CI: run tests with both Pageserver VirtualFile IO engines

Apart from sticking closer to the comment above the function,
this reduces the diff in the next patch.

.github/workflows/build_and_test.yml

@@ -341,7 +341,9 @@ jobs:
 
       - name: Run rust tests
         run: |
-          ${cov_prefix} cargo nextest run $CARGO_FLAGS $CARGO_FEATURES
+          for io_engine in std-fs tokio-epoll-uring ; do
+            NEON_PAGESERVER_UNIT_TEST_VIRTUAL_FILE_IOENGINE=$io_engine ${cov_prefix} cargo nextest run $CARGO_FLAGS $CARGO_FEATURES
+          done
 
           # Run separate tests for real S3
           export ENABLE_REAL_S3_REMOTE_STORAGE=nonempty
@@ -426,6 +428,7 @@ jobs:
       matrix:
         build_type: [ debug, release ]
         pg_version: [ v14, v15, v16 ]
+        pageserver_virtual_file_io_engine: [ std-fs, tokio-epoll-uring ]
     steps:
       - name: Checkout
         uses: actions/checkout@v3
@@ -448,6 +451,7 @@ jobs:
           TEST_RESULT_CONNSTR: ${{ secrets.REGRESS_TEST_RESULT_CONNSTR_NEW }}
           CHECK_ONDISK_DATA_COMPATIBILITY: nonempty
           BUILD_TAG: ${{ needs.tag.outputs.build-tag }}
+          PAGESERVER_VIRTUAL_FILE_IO_ENGINE: ${{ matrix.pageserver_virtual_file_io_engine }}
 
       - name: Merge and upload coverage data
         if: matrix.build_type == 'debug' && matrix.pg_version == 'v14'
@@ -466,6 +470,7 @@ jobs:
       matrix:
         pytest_split_group: [ 1, 2, 3, 4 ]
         build_type: [ release ]
+        pageserver_virtual_file_io_engine: [ std-fs, tokio-epoll-uring ]
     steps:
       - name: Checkout
         uses: actions/checkout@v3
@@ -482,6 +487,7 @@ jobs:
           VIP_VAP_ACCESS_TOKEN: "${{ secrets.VIP_VAP_ACCESS_TOKEN }}"
           PERF_TEST_RESULT_CONNSTR: "${{ secrets.PERF_TEST_RESULT_CONNSTR }}"
           TEST_RESULT_CONNSTR: "${{ secrets.REGRESS_TEST_RESULT_CONNSTR_NEW }}"
+          PAGESERVER_VIRTUAL_FILE_IO_ENGINE: "${{ matrix.pageserver_virtual_file_io_engine }}"
       # XXX: no coverage data handling here, since benchmarks are run on release builds,
       # while coverage is currently collected for the debug ones
 

Cargo.lock

@@ -2520,6 +2520,16 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "io-uring"
+version = "0.6.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "460648e47a07a43110fbfa2e0b14afb2be920093c31e5dccc50e49568e099762"
+dependencies = [
+ "bitflags 1.3.2",
+ "libc",
+]
+
 [[package]]
 name = "ipnet"
 version = "2.9.0"
@@ -3315,6 +3325,7 @@ dependencies = [
  "tenant_size_model",
  "thiserror",
  "tokio",
+ "tokio-epoll-uring",
  "tokio-io-timeout",
  "tokio-postgres",
  "tokio-stream",
@@ -5334,18 +5345,18 @@ dependencies = [
 
 [[package]]
 name = "thiserror"
-version = "1.0.40"
+version = "1.0.47"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "978c9a314bd8dc99be594bc3c175faaa9794be04a5a5e153caba6915336cebac"
+checksum = "97a802ec30afc17eee47b2855fc72e0c4cd62be9b4efe6591edde0ec5bd68d8f"
 dependencies = [
  "thiserror-impl",
 ]
 
 [[package]]
 name = "thiserror-impl"
-version = "1.0.40"
+version = "1.0.47"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f9456a42c5b0d803c8cd86e73dd7cc9edd429499f37a3550d286d5e86720569f"
+checksum = "6bb623b56e39ab7dcd4b1b98bb6c8f8d907ed255b18de254088016b27a8ee19b"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -5469,6 +5480,21 @@ dependencies = [
  "windows-sys 0.48.0",
 ]
 
+[[package]]
+name = "tokio-epoll-uring"
+version = "0.1.0"
+source = "git+https://github.com/neondatabase/tokio-epoll-uring.git?branch=main#9c5ea716add1357dc8c180167e43a2ae596eba68"
+dependencies = [
+ "futures",
+ "once_cell",
+ "scopeguard",
+ "thiserror",
+ "tokio",
+ "tokio-util",
+ "tracing",
+ "uring-common",
+]
+
 [[package]]
 name = "tokio-io-timeout"
 version = "1.2.0"
@@ -6020,6 +6046,15 @@ dependencies = [
  "webpki-roots 0.23.1",
 ]
 
+[[package]]
+name = "uring-common"
+version = "0.1.0"
+source = "git+https://github.com/neondatabase/tokio-epoll-uring.git?branch=main#9c5ea716add1357dc8c180167e43a2ae596eba68"
+dependencies = [
+ "io-uring",
+ "libc",
+]
+
 [[package]]
 name = "url"
 version = "2.3.1"

Cargo.toml

@@ -150,6 +150,8 @@ test-context = "0.1"
 thiserror = "1.0"
 tls-listener = { version = "0.7", features = ["rustls", "hyper-h1"] }
 tokio = { version = "1.17", features = ["macros"] }
+#tokio-epoll-uring = { path = "../tokio-epoll-uring/tokio-epoll-uring" }
+tokio-epoll-uring = { git = "https://github.com/neondatabase/tokio-epoll-uring.git" , branch = "main" }
 tokio-io-timeout = "1.2.0"
 tokio-postgres-rustls = "0.10.0"
 tokio-rustls = "0.24"

pageserver/Cargo.toml

@@ -61,6 +61,7 @@ sync_wrapper.workspace = true
 tokio-tar.workspace = true
 thiserror.workspace = true
 tokio = { workspace = true, features = ["process", "sync", "fs", "rt", "io-util", "time"] }
+tokio-epoll-uring.workspace = true
 tokio-io-timeout.workspace = true
 tokio-postgres.workspace = true
 tokio-stream.workspace = true

pageserver/ctl/src/layer_map_analyzer.rs

@@ -18,7 +18,7 @@ use pageserver::tenant::block_io::FileBlockReader;
 use pageserver::tenant::disk_btree::{DiskBtreeReader, VisitDirection};
 use pageserver::tenant::storage_layer::delta_layer::{Summary, DELTA_KEY_SIZE};
 use pageserver::tenant::storage_layer::range_overlaps;
-use pageserver::virtual_file::VirtualFile;
+use pageserver::virtual_file::{self, VirtualFile};
 
 use utils::{bin_ser::BeSer, lsn::Lsn};
 
@@ -142,7 +142,7 @@ pub(crate) async fn main(cmd: &AnalyzeLayerMapCmd) -> Result<()> {
     let ctx = RequestContext::new(TaskKind::DebugTool, DownloadBehavior::Error);
 
     // Initialize virtual_file (file desriptor cache) and page cache which are needed to access layer persistent B-Tree.
-    pageserver::virtual_file::init(10);
+    pageserver::virtual_file::init(10, virtual_file::IoEngineKind::StdFs);
     pageserver::page_cache::init(100);
 
     let mut total_delta_layers = 0usize;

pageserver/ctl/src/layers.rs

@@ -59,7 +59,7 @@ pub(crate) enum LayerCmd {
 
 async fn read_delta_file(path: impl AsRef<Path>, ctx: &RequestContext) -> Result<()> {
     let path = Utf8Path::from_path(path.as_ref()).expect("non-Unicode path");
-    virtual_file::init(10);
+    virtual_file::init(10, virtual_file::IoEngineKind::StdFs);
     page_cache::init(100);
     let file = FileBlockReader::new(VirtualFile::open(path).await?);
     let summary_blk = file.read_blk(0, ctx).await?;
@@ -187,7 +187,7 @@ pub(crate) async fn main(cmd: &LayerCmd) -> Result<()> {
             new_tenant_id,
             new_timeline_id,
         } => {
-            pageserver::virtual_file::init(10);
+            pageserver::virtual_file::init(10, virtual_file::IoEngineKind::StdFs);
             pageserver::page_cache::init(100);
 
             let ctx = RequestContext::new(TaskKind::DebugTool, DownloadBehavior::Error);

pageserver/ctl/src/main.rs

@@ -123,7 +123,7 @@ fn read_pg_control_file(control_file_path: &Utf8Path) -> anyhow::Result<()> {
 
 async fn print_layerfile(path: &Utf8Path) -> anyhow::Result<()> {
     // Basic initialization of things that don't change after startup
-    virtual_file::init(10);
+    virtual_file::init(10, virtual_file::IoEngineKind::StdFs);
     page_cache::init(100);
     let ctx = RequestContext::new(TaskKind::DebugTool, DownloadBehavior::Error);
     dump_layerfile_from_path(path, true, &ctx).await

pageserver/src/bin/pageserver.rs

@@ -130,7 +130,7 @@ fn main() -> anyhow::Result<()> {
     let scenario = failpoint_support::init();
 
     // Basic initialization of things that don't change after startup
-    virtual_file::init(conf.max_file_descriptors);
+    virtual_file::init(conf.max_file_descriptors, conf.virtual_file_io_engine);
     page_cache::init(conf.page_cache_size);
 
     start_pageserver(launch_ts, conf).context("Failed to start pageserver")?;

pageserver/src/config.rs

@@ -36,6 +36,7 @@ use crate::tenant::config::TenantConfOpt;
 use crate::tenant::{
     TENANTS_SEGMENT_NAME, TENANT_DELETED_MARKER_FILE_NAME, TIMELINES_SEGMENT_NAME,
 };
+use crate::virtual_file;
 use crate::{
     IGNORED_TENANT_FILE_NAME, METADATA_FILE_NAME, TENANT_CONFIG_NAME, TENANT_HEATMAP_BASENAME,
     TENANT_LOCATION_CONFIG_NAME, TIMELINE_DELETE_MARK_SUFFIX, TIMELINE_UNINIT_MARK_SUFFIX,
@@ -43,6 +44,8 @@ use crate::{
 
 use self::defaults::DEFAULT_CONCURRENT_TENANT_WARMUP;
 
+use self::defaults::DEFAULT_VIRTUAL_FILE_IO_ENGINE;
+
 pub mod defaults {
     use crate::tenant::config::defaults::*;
     use const_format::formatcp;
@@ -79,6 +82,8 @@ pub mod defaults {
 
     pub const DEFAULT_INGEST_BATCH_SIZE: u64 = 100;
 
+    pub const DEFAULT_VIRTUAL_FILE_IO_ENGINE: &str = "std-fs";
+
     ///
     /// Default built-in configuration file.
     ///
@@ -114,6 +119,8 @@ pub mod defaults {
 
 #ingest_batch_size = {DEFAULT_INGEST_BATCH_SIZE}
 
+#virtual_file_io_engine = '{DEFAULT_VIRTUAL_FILE_IO_ENGINE}'
+
 [tenant_config]
 #checkpoint_distance = {DEFAULT_CHECKPOINT_DISTANCE} # in bytes
 #checkpoint_timeout = {DEFAULT_CHECKPOINT_TIMEOUT}
@@ -247,6 +254,8 @@ pub struct PageServerConf {
 
     /// Maximum number of WAL records to be ingested and committed at the same time
     pub ingest_batch_size: u64,
+
+    pub virtual_file_io_engine: virtual_file::IoEngineKind,
 }
 
 /// We do not want to store this in a PageServerConf because the latter may be logged
@@ -331,6 +340,8 @@ struct PageServerConfigBuilder {
     secondary_download_concurrency: BuilderValue<usize>,
 
     ingest_batch_size: BuilderValue<u64>,
+
+    virtual_file_io_engine: BuilderValue<virtual_file::IoEngineKind>,
 }
 
 impl Default for PageServerConfigBuilder {
@@ -406,6 +417,8 @@ impl Default for PageServerConfigBuilder {
             secondary_download_concurrency: Set(DEFAULT_SECONDARY_DOWNLOAD_CONCURRENCY),
 
             ingest_batch_size: Set(DEFAULT_INGEST_BATCH_SIZE),
+
+            virtual_file_io_engine: Set(DEFAULT_VIRTUAL_FILE_IO_ENGINE.parse().unwrap()),
         }
     }
 }
@@ -562,6 +575,10 @@ impl PageServerConfigBuilder {
         self.ingest_batch_size = BuilderValue::Set(ingest_batch_size)
     }
 
+    pub fn virtual_file_io_engine(&mut self, value: virtual_file::IoEngineKind) {
+        self.virtual_file_io_engine = BuilderValue::Set(value);
+    }
+
     pub fn build(self) -> anyhow::Result<PageServerConf> {
         let concurrent_tenant_warmup = self
             .concurrent_tenant_warmup
@@ -669,6 +686,9 @@ impl PageServerConfigBuilder {
             ingest_batch_size: self
                 .ingest_batch_size
                 .ok_or(anyhow!("missing ingest_batch_size"))?,
+            virtual_file_io_engine: self
+                .virtual_file_io_engine
+                .ok_or(anyhow!("missing virtual_file_io_engine"))?,
         })
     }
 }
@@ -920,6 +940,9 @@ impl PageServerConf {
                     builder.secondary_download_concurrency(parse_toml_u64(key, item)? as usize)
                 },
                 "ingest_batch_size" => builder.ingest_batch_size(parse_toml_u64(key, item)?),
+                "virtual_file_io_engine" => {
+                    builder.virtual_file_io_engine(parse_toml_from_str("virtual_file_io_engine", item)?)
+                }
                 _ => bail!("unrecognized pageserver option '{key}'"),
             }
         }
@@ -993,6 +1016,7 @@ impl PageServerConf {
             heatmap_upload_concurrency: defaults::DEFAULT_HEATMAP_UPLOAD_CONCURRENCY,
             secondary_download_concurrency: defaults::DEFAULT_SECONDARY_DOWNLOAD_CONCURRENCY,
             ingest_batch_size: defaults::DEFAULT_INGEST_BATCH_SIZE,
+            virtual_file_io_engine: DEFAULT_VIRTUAL_FILE_IO_ENGINE.parse().unwrap(),
         }
     }
 }
@@ -1224,6 +1248,7 @@ background_task_maximum_delay = '334 s'
                 heatmap_upload_concurrency: defaults::DEFAULT_HEATMAP_UPLOAD_CONCURRENCY,
                 secondary_download_concurrency: defaults::DEFAULT_SECONDARY_DOWNLOAD_CONCURRENCY,
                 ingest_batch_size: defaults::DEFAULT_INGEST_BATCH_SIZE,
+                virtual_file_io_engine: DEFAULT_VIRTUAL_FILE_IO_ENGINE.parse().unwrap(),
             },
             "Correct defaults should be used when no config values are provided"
         );
@@ -1287,6 +1312,7 @@ background_task_maximum_delay = '334 s'
                 heatmap_upload_concurrency: defaults::DEFAULT_HEATMAP_UPLOAD_CONCURRENCY,
                 secondary_download_concurrency: defaults::DEFAULT_SECONDARY_DOWNLOAD_CONCURRENCY,
                 ingest_batch_size: 100,
+                virtual_file_io_engine: DEFAULT_VIRTUAL_FILE_IO_ENGINE.parse().unwrap(),
             },
             "Should be able to parse all basic config values correctly"
         );

pageserver/src/lib.rs

@@ -1,3 +1,4 @@
+#![recursion_limit = "300"]
 #![deny(clippy::undocumented_unsafe_blocks)]
 
 mod auth;

pageserver/src/metrics.rs

@@ -941,6 +941,7 @@ pub(crate) static STORAGE_IO_SIZE: Lazy<IntGaugeVec> = Lazy::new(|| {
     .expect("failed to define a metric")
 });
 
+#[cfg(not(test))]
 pub(crate) mod virtual_file_descriptor_cache {
     use super::*;
 

pageserver/src/tenant/block_io.rs

@@ -5,10 +5,10 @@
 use super::ephemeral_file::EphemeralFile;
 use super::storage_layer::delta_layer::{Adapter, DeltaLayerInner};
 use crate::context::RequestContext;
-use crate::page_cache::{self, PageReadGuard, ReadBufResult, PAGE_SZ};
+use crate::page_cache::{self, PageReadGuard, PageWriteGuard, ReadBufResult, PAGE_SZ};
 use crate::virtual_file::VirtualFile;
 use bytes::Bytes;
-use std::ops::{Deref, DerefMut};
+use std::ops::Deref;
 
 /// This is implemented by anything that can read 8 kB (PAGE_SZ)
 /// blocks, using the page cache
@@ -39,6 +39,8 @@ pub enum BlockLease<'a> {
     EphemeralFileMutableTail(&'a [u8; PAGE_SZ]),
     #[cfg(test)]
     Arc(std::sync::Arc<[u8; PAGE_SZ]>),
+    #[cfg(test)]
+    Vec(Vec<u8>),
 }
 
 impl From<PageReadGuard<'static>> for BlockLease<'static> {
@@ -63,6 +65,13 @@ impl<'a> Deref for BlockLease<'a> {
             BlockLease::EphemeralFileMutableTail(v) => v,
             #[cfg(test)]
             BlockLease::Arc(v) => v.deref(),
+            #[cfg(test)]
+            BlockLease::Vec(v) => {
+                let v: &Vec<u8> = v;
+                assert_eq!(v.len(), PAGE_SZ, "caller must ensure that v has PAGE_SZ");
+                // Safety: see above assertion.
+                unsafe { &*(v.as_ptr() as *const [u8; PAGE_SZ]) }
+            }
         }
     }
 }
@@ -169,10 +178,14 @@ impl FileBlockReader {
     }
 
     /// Read a page from the underlying file into given buffer.
-    async fn fill_buffer(&self, buf: &mut [u8], blkno: u32) -> Result<(), std::io::Error> {
+    async fn fill_buffer(
+        &self,
+        buf: PageWriteGuard<'static>,
+        blkno: u32,
+    ) -> Result<PageWriteGuard<'static>, std::io::Error> {
         assert!(buf.len() == PAGE_SZ);
         self.file
-            .read_exact_at(buf, blkno as u64 * PAGE_SZ as u64)
+            .read_exact_at_page(buf, blkno as u64 * PAGE_SZ as u64)
             .await
     }
     /// Read a block.
@@ -196,9 +209,9 @@ impl FileBlockReader {
                 )
             })? {
             ReadBufResult::Found(guard) => Ok(guard.into()),
-            ReadBufResult::NotFound(mut write_guard) => {
+            ReadBufResult::NotFound(write_guard) => {
                 // Read the page from disk into the buffer
-                self.fill_buffer(write_guard.deref_mut(), blknum).await?;
+                let write_guard = self.fill_buffer(write_guard, blknum).await?;
                 Ok(write_guard.mark_valid().into())
             }
         }

pageserver/src/tenant/ephemeral_file.rs

@@ -5,11 +5,11 @@ use crate::config::PageServerConf;
 use crate::context::RequestContext;
 use crate::page_cache::{self, PAGE_SZ};
 use crate::tenant::block_io::{BlockCursor, BlockLease, BlockReader};
-use crate::virtual_file::VirtualFile;
+use crate::virtual_file::{self, VirtualFile};
 use camino::Utf8PathBuf;
 use pageserver_api::shard::TenantShardId;
 use std::cmp::min;
-use std::fs::OpenOptions;
+
 use std::io::{self, ErrorKind};
 use std::ops::DerefMut;
 use std::sync::atomic::AtomicU64;
@@ -47,7 +47,10 @@ impl EphemeralFile {
 
         let file = VirtualFile::open_with_options(
             &filename,
-            OpenOptions::new().read(true).write(true).create(true),
+            virtual_file::OpenOptions::new()
+                .read(true)
+                .write(true)
+                .create(true),
         )
         .await?;
 
@@ -89,11 +92,10 @@ impl EphemeralFile {
                 page_cache::ReadBufResult::Found(guard) => {
                     return Ok(BlockLease::PageReadGuard(guard))
                 }
-                page_cache::ReadBufResult::NotFound(mut write_guard) => {
-                    let buf: &mut [u8] = write_guard.deref_mut();
-                    debug_assert_eq!(buf.len(), PAGE_SZ);
-                    self.file
-                        .read_exact_at(&mut buf[..], blknum as u64 * PAGE_SZ as u64)
+                page_cache::ReadBufResult::NotFound(write_guard) => {
+                    let write_guard = self
+                        .file
+                        .read_exact_at_page(write_guard, blknum as u64 * PAGE_SZ as u64)
                         .await?;
                     let read_guard = write_guard.mark_valid();
                     return Ok(BlockLease::PageReadGuard(read_guard));

pageserver/src/tenant/storage_layer/delta_layer.rs

@@ -36,7 +36,7 @@ use crate::tenant::block_io::{BlockBuf, BlockCursor, BlockLease, BlockReader, Fi
 use crate::tenant::disk_btree::{DiskBtreeBuilder, DiskBtreeReader, VisitDirection};
 use crate::tenant::storage_layer::{Layer, ValueReconstructResult, ValueReconstructState};
 use crate::tenant::Timeline;
-use crate::virtual_file::VirtualFile;
+use crate::virtual_file::{self, VirtualFile};
 use crate::{walrecord, TEMP_FILE_SUFFIX};
 use crate::{DELTA_FILE_MAGIC, STORAGE_FORMAT_VERSION};
 use anyhow::{bail, ensure, Context, Result};
@@ -649,7 +649,7 @@ impl DeltaLayer {
     {
         let file = VirtualFile::open_with_options(
             path,
-            &*std::fs::OpenOptions::new().read(true).write(true),
+            virtual_file::OpenOptions::new().read(true).write(true),
         )
         .await
         .with_context(|| format!("Failed to open file '{}'", path))?;

pageserver/src/tenant/storage_layer/image_layer.rs

@@ -34,7 +34,7 @@ use crate::tenant::storage_layer::{
     LayerAccessStats, ValueReconstructResult, ValueReconstructState,
 };
 use crate::tenant::Timeline;
-use crate::virtual_file::VirtualFile;
+use crate::virtual_file::{self, VirtualFile};
 use crate::{IMAGE_FILE_MAGIC, STORAGE_FORMAT_VERSION, TEMP_FILE_SUFFIX};
 use anyhow::{bail, ensure, Context, Result};
 use bytes::Bytes;
@@ -327,7 +327,7 @@ impl ImageLayer {
     {
         let file = VirtualFile::open_with_options(
             path,
-            &*std::fs::OpenOptions::new().read(true).write(true),
+            virtual_file::OpenOptions::new().read(true).write(true),
         )
         .await
         .with_context(|| format!("Failed to open file '{}'", path))?;
@@ -492,11 +492,15 @@ impl ImageLayerWriterInner {
             },
         );
         info!("new image layer {path}");
-        let mut file = VirtualFile::open_with_options(
-            &path,
-            std::fs::OpenOptions::new().write(true).create_new(true),
-        )
-        .await?;
+        let mut file = {
+            VirtualFile::open_with_options(
+                &path,
+                virtual_file::OpenOptions::new()
+                    .write(true)
+                    .create_new(true),
+            )
+            .await?
+        };
         // make room for the header block
         file.seek(SeekFrom::Start(PAGE_SZ as u64)).await?;
         let blob_writer = BlobWriter::new(file, PAGE_SZ as u64);

pageserver/src/virtual_file.rs

@@ -11,17 +11,27 @@
 //! src/backend/storage/file/fd.c
 //!
 use crate::metrics::{StorageIoOperation, STORAGE_IO_SIZE, STORAGE_IO_TIME_METRIC};
+
+use crate::page_cache::PageWriteGuard;
 use crate::tenant::TENANTS_SEGMENT_NAME;
 use camino::{Utf8Path, Utf8PathBuf};
 use once_cell::sync::OnceCell;
-use std::fs::{self, File, OpenOptions};
+use std::fs::{self, File};
 use std::io::{Error, ErrorKind, Seek, SeekFrom};
+use tokio_epoll_uring::IoBufMut;
+
+use std::os::fd::{AsRawFd, FromRawFd, IntoRawFd, OwnedFd, RawFd};
 use std::os::unix::fs::FileExt;
 use std::sync::atomic::{AtomicBool, AtomicUsize, Ordering};
 use tokio::sync::{RwLock, RwLockReadGuard, RwLockWriteGuard};
 use tokio::time::Instant;
 use utils::fs_ext;
 
+mod io_engine;
+mod open_options;
+pub use io_engine::IoEngineKind;
+pub(crate) use open_options::*;
+
 ///
 /// A virtual file descriptor. You can use this just like std::fs::File, but internally
 /// the underlying file is closed if the system is low on file descriptors,
@@ -104,7 +114,38 @@ struct SlotInner {
     tag: u64,
 
     /// the underlying file
-    file: Option<File>,
+    file: Option<OwnedFd>,
+}
+
+/// Impl of [`tokio_epoll_uring::IoBuf`] and [`tokio_epoll_uring::IoBufMut`] for [`PageWriteGuard`].
+struct PageWriteGuardBuf {
+    page: PageWriteGuard<'static>,
+    init_up_to: usize,
+}
+// Safety: the [`PageWriteGuard`] gives us exclusive ownership of the page cache slot,
+// and the location remains stable even if [`Self`] or the [`PageWriteGuard`] is moved.
+unsafe impl tokio_epoll_uring::IoBuf for PageWriteGuardBuf {
+    fn stable_ptr(&self) -> *const u8 {
+        self.page.as_ptr()
+    }
+    fn bytes_init(&self) -> usize {
+        self.init_up_to
+    }
+    fn bytes_total(&self) -> usize {
+        self.page.len()
+    }
+}
+// Safety: see above, plus: the ownership of [`PageWriteGuard`] means exclusive access,
+// hence it's safe to hand out the `stable_mut_ptr()`.
+unsafe impl tokio_epoll_uring::IoBufMut for PageWriteGuardBuf {
+    fn stable_mut_ptr(&mut self) -> *mut u8 {
+        self.page.as_mut_ptr()
+    }
+
+    unsafe fn set_init(&mut self, pos: usize) {
+        assert!(pos <= self.page.len());
+        self.init_up_to = pos;
+    }
 }
 
 impl OpenFiles {
@@ -272,6 +313,10 @@ macro_rules! with_file {
         let $ident = $this.lock_file().await?;
         observe_duration!($op, $($body)*)
     }};
+    ($this:expr, $op:expr, | mut $ident:ident | $($body:tt)*) => {{
+        let mut $ident = $this.lock_file().await?;
+        observe_duration!($op, $($body)*)
+    }};
 }
 
 impl VirtualFile {
@@ -315,7 +360,9 @@ impl VirtualFile {
         // NB: there is also StorageIoOperation::OpenAfterReplace which is for the case
         // where our caller doesn't get to use the returned VirtualFile before its
         // slot gets re-used by someone else.
-        let file = observe_duration!(StorageIoOperation::Open, open_options.open(path))?;
+        let file = observe_duration!(StorageIoOperation::Open, {
+            open_options.open(path.as_std_path()).await?
+        });
 
         // Strip all options other than read and write.
         //
@@ -388,15 +435,13 @@ impl VirtualFile {
 
     /// Call File::sync_all() on the underlying File.
     pub async fn sync_all(&self) -> Result<(), Error> {
-        with_file!(self, StorageIoOperation::Fsync, |file| file
-            .as_ref()
-            .sync_all())
+        with_file!(self, StorageIoOperation::Fsync, |file_guard| file_guard
+            .with_std_file(|std_file| std_file.sync_all()))
     }
 
     pub async fn metadata(&self) -> Result<fs::Metadata, Error> {
-        with_file!(self, StorageIoOperation::Metadata, |file| file
-            .as_ref()
-            .metadata())
+        with_file!(self, StorageIoOperation::Metadata, |file_guard| file_guard
+            .with_std_file(|std_file| std_file.metadata()))
     }
 
     /// Helper function internal to `VirtualFile` that looks up the underlying File,
@@ -405,7 +450,7 @@ impl VirtualFile {
     ///
     /// We are doing it via a macro as Rust doesn't support async closures that
     /// take on parameters with lifetimes.
-    async fn lock_file(&self) -> Result<FileGuard<'_>, Error> {
+    async fn lock_file(&self) -> Result<FileGuard, Error> {
         let open_files = get_open_files();
 
         let mut handle_guard = {
@@ -451,10 +496,9 @@ impl VirtualFile {
         // NB: we use StorageIoOperation::OpenAferReplace for this to distinguish this
         // case from StorageIoOperation::Open. This helps with identifying thrashing
         // of the virtual file descriptor cache.
-        let file = observe_duration!(
-            StorageIoOperation::OpenAfterReplace,
-            self.open_options.open(&self.path)
-        )?;
+        let file = observe_duration!(StorageIoOperation::OpenAfterReplace, {
+            self.open_options.open(self.path.as_std_path()).await?
+        });
 
         // Store the File in the slot and update the handle in the VirtualFile
         // to point to it.
@@ -479,9 +523,8 @@ impl VirtualFile {
                 self.pos = offset;
             }
             SeekFrom::End(offset) => {
-                self.pos = with_file!(self, StorageIoOperation::Seek, |file| file
-                    .as_ref()
-                    .seek(SeekFrom::End(offset)))?
+                self.pos = with_file!(self, StorageIoOperation::Seek, |mut file_guard| file_guard
+                    .with_std_file_mut(|std_file| std_file.seek(SeekFrom::End(offset))))?
             }
             SeekFrom::Current(offset) => {
                 let pos = self.pos as i128 + offset as i128;
@@ -501,24 +544,48 @@ impl VirtualFile {
     }
 
     // Copied from https://doc.rust-lang.org/1.72.0/src/std/os/unix/fs.rs.html#117-135
-    pub async fn read_exact_at(&self, mut buf: &mut [u8], mut offset: u64) -> Result<(), Error> {
-        while !buf.is_empty() {
-            match self.read_at(buf, offset).await {
-                Ok(0) => {
-                    return Err(Error::new(
-                        std::io::ErrorKind::UnexpectedEof,
-                        "failed to fill whole buffer",
-                    ))
-                }
+    pub async fn read_exact_at<B>(&self, buf: B, mut offset: u64) -> Result<B, Error>
+    where
+        B: IoBufMut + Send,
+    {
+        use tokio_epoll_uring::BoundedBuf;
+        let mut buf: tokio_epoll_uring::Slice<B> = buf.slice_full();
+        while buf.bytes_total() != 0 {
+            let res;
+            (buf, res) = self.read_at(buf, offset).await;
+            match res {
+                Ok(0) => break,
                 Ok(n) => {
-                    buf = &mut buf[n..];
+                    buf = buf.slice(n..);
                     offset += n as u64;
                 }
                 Err(ref e) if e.kind() == std::io::ErrorKind::Interrupted => {}
                 Err(e) => return Err(e),
             }
         }
-        Ok(())
+        if !buf.is_empty() {
+            Err(std::io::Error::new(
+                std::io::ErrorKind::UnexpectedEof,
+                "failed to fill whole buffer",
+            ))
+        } else {
+            Ok(buf.into_inner())
+        }
+    }
+
+    /// Like [`Self::read_exact_at`] but for [`PageWriteGuard`].
+    pub async fn read_exact_at_page(
+        &self,
+        page: PageWriteGuard<'static>,
+        offset: u64,
+    ) -> Result<PageWriteGuard<'static>, Error> {
+        let buf = PageWriteGuardBuf {
+            page,
+            init_up_to: 0,
+        };
+        let res = self.read_exact_at(buf, offset).await;
+        res.map(|PageWriteGuardBuf { page, .. }| page)
+            .map_err(|e| Error::new(ErrorKind::Other, e))
     }
 
     // Copied from https://doc.rust-lang.org/1.72.0/src/std/os/unix/fs.rs.html#219-235
@@ -568,22 +635,30 @@ impl VirtualFile {
         Ok(n)
     }
 
-    pub async fn read_at(&self, buf: &mut [u8], offset: u64) -> Result<usize, Error> {
-        let result = with_file!(self, StorageIoOperation::Read, |file| file
-            .as_ref()
-            .read_at(buf, offset));
-        if let Ok(size) = result {
-            STORAGE_IO_SIZE
-                .with_label_values(&["read", &self.tenant_id, &self.timeline_id])
-                .add(size as i64);
-        }
-        result
+    pub(crate) async fn read_at<B>(&self, buf: B, offset: u64) -> (B, Result<usize, Error>)
+    where
+        B: tokio_epoll_uring::BoundedBufMut + Send,
+    {
+        let file_guard = match self.lock_file().await {
+            Ok(file_guard) => file_guard,
+            Err(e) => return (buf, Err(e)),
+        };
+
+        observe_duration!(StorageIoOperation::Read, {
+            let ((_file_guard, buf), res) = io_engine::get().read_at(file_guard, offset, buf).await;
+            if let Ok(size) = res {
+                STORAGE_IO_SIZE
+                    .with_label_values(&["read", &self.tenant_id, &self.timeline_id])
+                    .add(size as i64);
+            }
+            (buf, res)
+        })
     }
 
     async fn write_at(&self, buf: &[u8], offset: u64) -> Result<usize, Error> {
-        let result = with_file!(self, StorageIoOperation::Write, |file| file
-            .as_ref()
-            .write_at(buf, offset));
+        let result = with_file!(self, StorageIoOperation::Write, |file_guard| {
+            file_guard.with_std_file(|std_file| std_file.write_at(buf, offset))
+        });
         if let Ok(size) = result {
             STORAGE_IO_SIZE
                 .with_label_values(&["write", &self.tenant_id, &self.timeline_id])
@@ -593,18 +668,54 @@ impl VirtualFile {
     }
 }
 
-struct FileGuard<'a> {
-    slot_guard: RwLockReadGuard<'a, SlotInner>,
+struct FileGuard {
+    slot_guard: RwLockReadGuard<'static, SlotInner>,
 }
 
-impl<'a> AsRef<File> for FileGuard<'a> {
-    fn as_ref(&self) -> &File {
+impl AsRef<OwnedFd> for FileGuard {
+    fn as_ref(&self) -> &OwnedFd {
         // This unwrap is safe because we only create `FileGuard`s
         // if we know that the file is Some.
         self.slot_guard.file.as_ref().unwrap()
     }
 }
 
+impl FileGuard {
+    /// Soft deprecation: we'll move VirtualFile to async APIs and remove this function eventually.
+    fn with_std_file<F, R>(&self, with: F) -> R
+    where
+        F: FnOnce(&File) -> R,
+    {
+        // SAFETY:
+        // - lifetime of the fd: `file` doesn't outlive the OwnedFd stored in `self`.
+        // - `&` usage below: `self` is `&`, hence Rust typesystem guarantees there are is no `&mut`
+        let file = unsafe { File::from_raw_fd(self.as_ref().as_raw_fd()) };
+        let res = with(&file);
+        let _ = file.into_raw_fd();
+        res
+    }
+    /// Soft deprecation: we'll move VirtualFile to async APIs and remove this function eventually.
+    fn with_std_file_mut<F, R>(&mut self, with: F) -> R
+    where
+        F: FnOnce(&mut File) -> R,
+    {
+        // SAFETY:
+        // - lifetime of the fd: `file` doesn't outlive the OwnedFd stored in `self`.
+        // - &mut usage below: `self` is `&mut`, hence this call is the only task/thread that has control over the underlying fd
+        let mut file = unsafe { File::from_raw_fd(self.as_ref().as_raw_fd()) };
+        let res = with(&mut file);
+        let _ = file.into_raw_fd();
+        res
+    }
+}
+
+impl tokio_epoll_uring::IoFd for FileGuard {
+    unsafe fn as_fd(&self) -> RawFd {
+        let owned_fd: &OwnedFd = self.as_ref();
+        owned_fd.as_raw_fd()
+    }
+}
+
 #[cfg(test)]
 impl VirtualFile {
     pub(crate) async fn read_blk(
@@ -612,16 +723,19 @@ impl VirtualFile {
         blknum: u32,
     ) -> Result<crate::tenant::block_io::BlockLease<'_>, std::io::Error> {
         use crate::page_cache::PAGE_SZ;
-        let mut buf = [0; PAGE_SZ];
-        self.read_exact_at(&mut buf, blknum as u64 * (PAGE_SZ as u64))
+        let buf = vec![0; PAGE_SZ];
+        let buf = self
+            .read_exact_at(buf, blknum as u64 * (PAGE_SZ as u64))
             .await?;
-        Ok(std::sync::Arc::new(buf).into())
+        Ok(crate::tenant::block_io::BlockLease::Vec(buf))
     }
 
     async fn read_to_end(&mut self, buf: &mut Vec<u8>) -> Result<(), Error> {
+        let mut tmp = vec![0; 128];
         loop {
-            let mut tmp = [0; 128];
-            match self.read_at(&mut tmp, self.pos).await {
+            let res;
+            (tmp, res) = self.read_at(tmp, self.pos).await;
+            match res {
                 Ok(0) => return Ok(()),
                 Ok(n) => {
                     self.pos += n as u64;
@@ -697,10 +811,12 @@ impl OpenFiles {
 /// Initialize the virtual file module. This must be called once at page
 /// server startup.
 ///
-pub fn init(num_slots: usize) {
+#[cfg(not(test))]
+pub fn init(num_slots: usize, engine: IoEngineKind) {
     if OPEN_FILES.set(OpenFiles::new(num_slots)).is_err() {
         panic!("virtual_file::init called twice");
     }
+    io_engine::init(engine);
     crate::metrics::virtual_file_descriptor_cache::SIZE_MAX.set(num_slots as u64);
 }
 
@@ -745,10 +861,10 @@ mod tests {
     }
 
     impl MaybeVirtualFile {
-        async fn read_exact_at(&self, buf: &mut [u8], offset: u64) -> Result<(), Error> {
+        async fn read_exact_at(&self, mut buf: Vec<u8>, offset: u64) -> Result<Vec<u8>, Error> {
             match self {
                 MaybeVirtualFile::VirtualFile(file) => file.read_exact_at(buf, offset).await,
-                MaybeVirtualFile::File(file) => file.read_exact_at(buf, offset),
+                MaybeVirtualFile::File(file) => file.read_exact_at(&mut buf, offset).map(|()| buf),
             }
         }
         async fn write_all_at(&self, buf: &[u8], offset: u64) -> Result<(), Error> {
@@ -790,14 +906,14 @@ mod tests {
 
         // Helper function to slurp a portion of a file into a string
         async fn read_string_at(&mut self, pos: u64, len: usize) -> Result<String, Error> {
-            let mut buf = vec![0; len];
-            self.read_exact_at(&mut buf, pos).await?;
+            let buf = vec![0; len];
+            let buf = self.read_exact_at(buf, pos).await?;
             Ok(String::from_utf8(buf).unwrap())
         }
     }
 
     #[tokio::test]
-    async fn test_virtual_files() -> Result<(), Error> {
+    async fn test_virtual_files() -> anyhow::Result<()> {
         // The real work is done in the test_files() helper function. This
         // allows us to run the same set of tests against a native File, and
         // VirtualFile. We trust the native Files and wouldn't need to test them,
@@ -813,14 +929,17 @@ mod tests {
     }
 
     #[tokio::test]
-    async fn test_physical_files() -> Result<(), Error> {
+    async fn test_physical_files() -> anyhow::Result<()> {
         test_files("physical_files", |path, open_options| async move {
-            Ok(MaybeVirtualFile::File(open_options.open(path)?))
+            Ok(MaybeVirtualFile::File({
+                let owned_fd = open_options.open(path.as_std_path()).await?;
+                File::from(owned_fd)
+            }))
         })
         .await
     }
 
-    async fn test_files<OF, FT>(testname: &str, openfunc: OF) -> Result<(), Error>
+    async fn test_files<OF, FT>(testname: &str, openfunc: OF) -> anyhow::Result<()>
     where
         OF: Fn(Utf8PathBuf, OpenOptions) -> FT,
         FT: Future<Output = Result<MaybeVirtualFile, std::io::Error>>,
@@ -964,11 +1083,11 @@ mod tests {
         for _threadno in 0..THREADS {
             let files = files.clone();
             let hdl = rt.spawn(async move {
-                let mut buf = [0u8; SIZE];
+                let mut buf = vec![0u8; SIZE];
                 let mut rng = rand::rngs::OsRng;
                 for _ in 1..1000 {
                     let f = &files[rng.gen_range(0..files.len())];
-                    f.read_exact_at(&mut buf, 0).await.unwrap();
+                    buf = f.read_exact_at(buf, 0).await.unwrap();
                     assert!(buf == SAMPLE);
                 }
             });

pageserver/src/virtual_file/io_engine.rs

@@ -0,0 +1,109 @@
+//! [`super::VirtualFile`] supports different IO engines.
+//!
+//! The [`IoEngineKind`] enum identifies them.
+//!
+//! The choice of IO engine is global.
+//! Initialize using [`init`].
+//!
+//! Then use [`get`] and  [`OpenOptions`].
+
+#[derive(
+    Copy,
+    Clone,
+    PartialEq,
+    Eq,
+    Hash,
+    strum_macros::EnumString,
+    strum_macros::Display,
+    serde_with::DeserializeFromStr,
+    serde_with::SerializeDisplay,
+    Debug,
+)]
+#[strum(serialize_all = "kebab-case")]
+pub enum IoEngineKind {
+    StdFs,
+    TokioEpollUring,
+}
+
+static IO_ENGINE: once_cell::sync::OnceCell<IoEngineKind> = once_cell::sync::OnceCell::new();
+
+#[cfg(not(test))]
+pub(super) fn init(engine: IoEngineKind) {
+    if IO_ENGINE.set(engine).is_err() {
+        panic!("called twice");
+    }
+}
+
+pub(super) fn get() -> &'static IoEngineKind {
+    #[cfg(test)]
+    {
+        let env_var_name = "NEON_PAGESERVER_UNIT_TEST_VIRTUAL_FILE_IOENGINE";
+        IO_ENGINE.get_or_init(|| match std::env::var(env_var_name) {
+            Ok(v) => match v.parse::<IoEngineKind>() {
+                Ok(engine_kind) => engine_kind,
+                Err(e) => {
+                    panic!("invalid VirtualFile io engine for env var {env_var_name}: {e:#}: {v:?}")
+                }
+            },
+            Err(std::env::VarError::NotPresent) => {
+                crate::config::defaults::DEFAULT_VIRTUAL_FILE_IO_ENGINE
+                    .parse()
+                    .unwrap()
+            }
+            Err(std::env::VarError::NotUnicode(_)) => {
+                panic!("env var {env_var_name} is not unicode");
+            }
+        })
+    }
+    #[cfg(not(test))]
+    IO_ENGINE.get().unwrap()
+}
+
+use std::os::unix::prelude::FileExt;
+
+use super::FileGuard;
+
+impl IoEngineKind {
+    pub(super) async fn read_at<B>(
+        &self,
+        file_guard: FileGuard,
+        offset: u64,
+        mut buf: B,
+    ) -> ((FileGuard, B), std::io::Result<usize>)
+    where
+        B: tokio_epoll_uring::BoundedBufMut + Send,
+    {
+        match self {
+            IoEngineKind::StdFs => {
+                // SAFETY: `dst` only lives at most as long as this match arm, during which buf remains valid memory.
+                let dst = unsafe {
+                    std::slice::from_raw_parts_mut(buf.stable_mut_ptr(), buf.bytes_total())
+                };
+                let res = file_guard.with_std_file(|std_file| std_file.read_at(dst, offset));
+                if let Ok(nbytes) = &res {
+                    assert!(*nbytes <= buf.bytes_total());
+                    // SAFETY: see above assertion
+                    unsafe {
+                        buf.set_init(*nbytes);
+                    }
+                }
+                #[allow(dropping_references)]
+                drop(dst);
+                ((file_guard, buf), res)
+            }
+            IoEngineKind::TokioEpollUring => {
+                let system = tokio_epoll_uring::thread_local_system().await;
+                let (resources, res) = system.read(file_guard, offset, buf).await;
+                (
+                    resources,
+                    res.map_err(|e| match e {
+                        tokio_epoll_uring::Error::Op(e) => e,
+                        tokio_epoll_uring::Error::System(system) => {
+                            std::io::Error::new(std::io::ErrorKind::Other, system)
+                        }
+                    }),
+                )
+            }
+        }
+    }
+}

pageserver/src/virtual_file/open_options.rs

@@ -0,0 +1,129 @@
+//! Enum-dispatch to the `OpenOptions` type of the respective [`super::IoEngineKind`];
+
+use std::{os::fd::OwnedFd, path::Path};
+
+use super::IoEngineKind;
+
+#[derive(Debug, Clone)]
+pub enum OpenOptions {
+    StdFs(std::fs::OpenOptions),
+    TokioEpollUring(tokio_epoll_uring::ops::open_at::OpenOptions),
+}
+
+impl Default for OpenOptions {
+    fn default() -> Self {
+        match super::io_engine::get() {
+            IoEngineKind::StdFs => Self::StdFs(std::fs::OpenOptions::new()),
+            IoEngineKind::TokioEpollUring => {
+                Self::TokioEpollUring(tokio_epoll_uring::ops::open_at::OpenOptions::new())
+            }
+        }
+    }
+}
+
+impl OpenOptions {
+    pub fn new() -> OpenOptions {
+        Self::default()
+    }
+
+    pub fn read(&mut self, read: bool) -> &mut OpenOptions {
+        match self {
+            OpenOptions::StdFs(x) => {
+                let _ = x.read(read);
+            }
+            OpenOptions::TokioEpollUring(x) => {
+                let _ = x.read(read);
+            }
+        }
+        self
+    }
+
+    pub fn write(&mut self, write: bool) -> &mut OpenOptions {
+        match self {
+            OpenOptions::StdFs(x) => {
+                let _ = x.write(write);
+            }
+            OpenOptions::TokioEpollUring(x) => {
+                let _ = x.write(write);
+            }
+        }
+        self
+    }
+
+    pub fn create(&mut self, create: bool) -> &mut OpenOptions {
+        match self {
+            OpenOptions::StdFs(x) => {
+                let _ = x.create(create);
+            }
+            OpenOptions::TokioEpollUring(x) => {
+                let _ = x.create(create);
+            }
+        }
+        self
+    }
+
+    pub fn create_new(&mut self, create_new: bool) -> &mut OpenOptions {
+        match self {
+            OpenOptions::StdFs(x) => {
+                let _ = x.create_new(create_new);
+            }
+            OpenOptions::TokioEpollUring(x) => {
+                let _ = x.create_new(create_new);
+            }
+        }
+        self
+    }
+
+    pub fn truncate(&mut self, truncate: bool) -> &mut OpenOptions {
+        match self {
+            OpenOptions::StdFs(x) => {
+                let _ = x.truncate(truncate);
+            }
+            OpenOptions::TokioEpollUring(x) => {
+                let _ = x.truncate(truncate);
+            }
+        }
+        self
+    }
+
+    pub(in crate::virtual_file) async fn open(&self, path: &Path) -> std::io::Result<OwnedFd> {
+        match self {
+            OpenOptions::StdFs(x) => x.open(path).map(|file| file.into()),
+            OpenOptions::TokioEpollUring(x) => {
+                let system = tokio_epoll_uring::thread_local_system().await;
+                system.open(path, x).await.map_err(|e| match e {
+                    tokio_epoll_uring::Error::Op(e) => e,
+                    tokio_epoll_uring::Error::System(system) => {
+                        std::io::Error::new(std::io::ErrorKind::Other, system)
+                    }
+                })
+            }
+        }
+    }
+}
+
+impl std::os::unix::prelude::OpenOptionsExt for OpenOptions {
+    fn mode(&mut self, mode: u32) -> &mut OpenOptions {
+        match self {
+            OpenOptions::StdFs(x) => {
+                let _ = x.mode(mode);
+            }
+            OpenOptions::TokioEpollUring(x) => {
+                let _ = x.mode(mode);
+            }
+        }
+        self
+    }
+
+    fn custom_flags(&mut self, flags: i32) -> &mut OpenOptions {
+        match self {
+            OpenOptions::StdFs(x) => {
+                let _ = x.custom_flags(flags);
+            }
+            OpenOptions::TokioEpollUring(x) => {
+                let _ = x.custom_flags(flags);
+            }
+        }
+        self
+    }
+}

test_runner/fixtures/neon_fixtures.py

@@ -440,6 +440,7 @@ class NeonEnvBuilder:
         preserve_database_files: bool = False,
         initial_tenant: Optional[TenantId] = None,
         initial_timeline: Optional[TimelineId] = None,
+        pageserver_virtual_file_io_engine: Optional[str] = None,
     ):
         self.repo_dir = repo_dir
         self.rust_log_override = rust_log_override
@@ -473,6 +474,8 @@ class NeonEnvBuilder:
         self.test_overlay_dir = test_overlay_dir
         self.overlay_mounts_created_by_us: List[Tuple[str, Path]] = []
 
+        self.pageserver_virtual_file_io_engine: Optional[str] = pageserver_virtual_file_io_engine
+
         assert test_name.startswith(
             "test_"
         ), "Unexpectedly instantiated from outside a test function"
@@ -870,6 +873,8 @@ class NeonEnv:
         self.control_plane_api: str = f"http://127.0.0.1:{attachment_service_port}"
         self.attachment_service: NeonAttachmentService = NeonAttachmentService(self)
 
+        self.pageserver_virtual_file_io_engine = config.pageserver_virtual_file_io_engine
+
         # Create a config file corresponding to the options
         cfg: Dict[str, Any] = {
             "default_tenant_id": str(self.initial_tenant),
@@ -901,6 +906,9 @@ class NeonEnv:
                 "pg_auth_type": pg_auth_type,
                 "http_auth_type": http_auth_type,
             }
+            if self.pageserver_virtual_file_io_engine is not None:
+                ps_cfg["virtual_file_io_engine"] = self.pageserver_virtual_file_io_engine
+
             # Create a corresponding NeonPageserver object
             self.pageservers.append(
                 NeonPageserver(
@@ -1040,6 +1048,7 @@ def _shared_simple_env(
     neon_binpath: Path,
     pg_distrib_dir: Path,
     pg_version: PgVersion,
+    pageserver_virtual_file_io_engine: str,
 ) -> Iterator[NeonEnv]:
     """
     # Internal fixture backing the `neon_simple_env` fixture. If TEST_SHARED_FIXTURES
@@ -1068,6 +1077,7 @@ def _shared_simple_env(
         preserve_database_files=pytestconfig.getoption("--preserve-database-files"),
         test_name=request.node.name,
         test_output_dir=test_output_dir,
+        pageserver_virtual_file_io_engine=pageserver_virtual_file_io_engine,
     ) as builder:
         env = builder.init_start()
 
@@ -1105,6 +1115,7 @@ def neon_env_builder(
     run_id: uuid.UUID,
     request: FixtureRequest,
     test_overlay_dir: Path,
+    pageserver_virtual_file_io_engine: str,
 ) -> Iterator[NeonEnvBuilder]:
     """
     Fixture to create a Neon environment for test.
@@ -1133,6 +1144,7 @@ def neon_env_builder(
         broker=default_broker,
         run_id=run_id,
         preserve_database_files=pytestconfig.getoption("--preserve-database-files"),
+        pageserver_virtual_file_io_engine=pageserver_virtual_file_io_engine,
         test_name=request.node.name,
         test_output_dir=test_output_dir,
         test_overlay_dir=test_overlay_dir,

test_runner/fixtures/parametrize.py

@@ -8,7 +8,7 @@ from _pytest.python import Metafunc
 from fixtures.pg_version import PgVersion
 
 """
-Dynamically parametrize tests by Postgres version and build type (debug/release/remote)
+Dynamically parametrize tests by Postgres version, build type (debug/release/remote), and possibly by other parameters
 """
 
 
@@ -31,11 +31,12 @@ def build_type(request: FixtureRequest) -> Optional[str]:
     return None
 
 
-def pytest_generate_tests(metafunc: Metafunc):
-    # Do not parametrize performance tests yet, we need to prepare grafana charts first
-    if "test_runner/performance" in metafunc.definition._nodeid:
-        return
+@pytest.fixture(scope="function", autouse=True)
+def pageserver_virtual_file_io_engine(request: FixtureRequest) -> Optional[str]:
+    return None
 
+
+def pytest_generate_tests(metafunc: Metafunc):
     if (v := os.environ.get("DEFAULT_PG_VERSION")) is None:
         pg_versions = [version for version in PgVersion if version != PgVersion.NOT_SET]
     else:
@@ -46,5 +47,14 @@ def pytest_generate_tests(metafunc: Metafunc):
     else:
         build_types = [bt.lower()]
 
+    # A hacky way to parametrize performance tests only for `pageserver_virtual_file_io_engine=tokio-epoll-uring`
+    # And do not change test name for default `pageserver_virtual_file_io_engine=std-fs` to keep perf tests statistics
+    if (io_engine := os.environ.get("PAGESERVER_VIRTUAL_FILE_IO_ENGINE", "")) not in ("", "std-fs"):
+        metafunc.parametrize("pageserver_virtual_file_io_engine", [io_engine])
+
+    # Do not parametrize performance tests yet by Postgres version or build type, we need to prepare grafana charts first
+    if "test_runner/performance" in metafunc.definition._nodeid:
+        return
+
     metafunc.parametrize("build_type", build_types)
     metafunc.parametrize("pg_version", pg_versions, ids=map(lambda v: f"pg{v}", pg_versions))