pageserver: don't evict metadata layers

.cargo/config.toml

@@ -1,17 +1,3 @@
-# The binaries are really slow, if you compile them in 'dev' mode with the defaults.
-# Enable some optimizations even in 'dev' mode, to make tests faster. The basic
-# optimizations enabled by "opt-level=1" don't affect debuggability too much.
-#
-# See https://www.reddit.com/r/rust/comments/gvrgca/this_is_a_neat_trick_for_getting_good_runtime/
-#
-[profile.dev.package."*"]
-# Set the default for dependencies in Development mode.
-opt-level = 3
-
-[profile.dev]
-# Turn on a small amount of optimization in Development mode.
-opt-level = 1
-
 [build]
 # This is only present for local builds, as it will be overridden
 # by the RUSTDOCFLAGS env var in CI.

pageserver/src/keyspace.rs

@@ -1,4 +1,7 @@
-use crate::repository::{key_range_size, singleton_range, Key};
+use crate::{
+    pgdatadir_mapping::{BASEBACKUP_CUT, METADATA_CUT},
+    repository::{key_range_size, singleton_range, Key},
+};
 use postgres_ffi::BLCKSZ;
 use std::ops::Range;
 
@@ -22,13 +25,22 @@ impl KeySpace {
         let target_nblocks = (target_size / BLCKSZ as u64) as usize;
 
         let mut parts = Vec::new();
-        let mut current_part = Vec::new();
+        let mut current_part: Vec<Range<Key>> = Vec::new();
         let mut current_part_size: usize = 0;
         for range in &self.ranges {
+            let last = current_part
+                .last()
+                .map(|r| r.end)
+                .unwrap_or(Key::from_i128(0));
+            let cut_here = (range.start >= METADATA_CUT && last < METADATA_CUT)
+                || (range.start >= BASEBACKUP_CUT && last < BASEBACKUP_CUT);
+
             // If appending the next contiguous range in the keyspace to the current
             // partition would cause it to be too large, start a new partition.
             let this_size = key_range_size(range) as usize;
-            if current_part_size + this_size > target_nblocks && !current_part.is_empty() {
+            if cut_here
+                || current_part_size + this_size > target_nblocks && !current_part.is_empty()
+            {
                 parts.push(KeySpace {
                     ranges: current_part,
                 });

pageserver/src/metrics.rs

@@ -40,9 +40,6 @@ pub enum StorageTimeOperation {
     #[strum(serialize = "logical size")]
     LogicalSize,
 
-    #[strum(serialize = "imitate logical size")]
-    ImitateLogicalSize,
-
     #[strum(serialize = "load layer map")]
     LoadLayerMap,
 
@@ -1364,7 +1361,6 @@ pub struct TimelineMetrics {
     pub compact_time_histo: StorageTimeMetrics,
     pub create_images_time_histo: StorageTimeMetrics,
     pub logical_size_histo: StorageTimeMetrics,
-    pub imitate_logical_size_histo: StorageTimeMetrics,
     pub load_layer_map_histo: StorageTimeMetrics,
     pub garbage_collect_histo: StorageTimeMetrics,
     pub last_record_gauge: IntGauge,
@@ -1393,11 +1389,6 @@ impl TimelineMetrics {
             StorageTimeMetrics::new(StorageTimeOperation::CreateImages, &tenant_id, &timeline_id);
         let logical_size_histo =
             StorageTimeMetrics::new(StorageTimeOperation::LogicalSize, &tenant_id, &timeline_id);
-        let imitate_logical_size_histo = StorageTimeMetrics::new(
-            StorageTimeOperation::ImitateLogicalSize,
-            &tenant_id,
-            &timeline_id,
-        );
         let load_layer_map_histo =
             StorageTimeMetrics::new(StorageTimeOperation::LoadLayerMap, &tenant_id, &timeline_id);
         let garbage_collect_histo =
@@ -1430,7 +1421,6 @@ impl TimelineMetrics {
             compact_time_histo,
             create_images_time_histo,
             logical_size_histo,
-            imitate_logical_size_histo,
             garbage_collect_histo,
             load_layer_map_histo,
             last_record_gauge,

pageserver/src/pgdatadir_mapping.rs

@@ -662,20 +662,21 @@ impl Timeline {
         ctx: &RequestContext,
     ) -> Result<KeySpace, CollectKeySpaceError> {
         // Iterate through key ranges, greedily packing them into partitions
+        // This function is responsible for appending keys in order, using implicit
+        // knowledge of how keys are defined.
         let mut result = KeySpaceAccum::new();
 
-        // The dbdir metadata always exists
-        result.add_key(DBDIR_KEY);
-
         // Fetch list of database dirs and iterate them
         let buf = self.get(DBDIR_KEY, lsn, ctx).await?;
         let dbdir = DbDirectory::des(&buf)?;
 
+        let mut metadata_keys = Vec::new();
+
         let mut dbs: Vec<(Oid, Oid)> = dbdir.dbdirs.keys().cloned().collect();
         dbs.sort_unstable();
         for (spcnode, dbnode) in dbs {
-            result.add_key(relmap_file_key(spcnode, dbnode));
-            result.add_key(rel_dir_to_key(spcnode, dbnode));
+            metadata_keys.push(relmap_file_key(spcnode, dbnode));
+            metadata_keys.push(rel_dir_to_key(spcnode, dbnode));
 
             let mut rels: Vec<RelTag> = self
                 .list_rels(spcnode, dbnode, lsn, ctx)
@@ -689,7 +690,7 @@ impl Timeline {
                 let relsize = buf.get_u32_le();
 
                 result.add_range(rel_block_to_key(rel, 0)..rel_block_to_key(rel, relsize));
-                result.add_key(relsize_key);
+                metadata_keys.push(relsize_key);
             }
         }
 
@@ -732,6 +733,13 @@ impl Timeline {
         if self.get(AUX_FILES_KEY, lsn, ctx).await.is_ok() {
             result.add_key(AUX_FILES_KEY);
         }
+
+        // The dbdir metadata always exists
+        result.add_key(DBDIR_KEY);
+        for key in metadata_keys {
+            result.add_key(key);
+        }
+
         Ok(result.to_keyspace())
     }
 
@@ -1474,21 +1482,11 @@ static ZERO_PAGE: Bytes = Bytes::from_static(&[0u8; BLCKSZ as usize]);
 //
 // Below is a full list of the keyspace allocation:
 //
-// DbDir:
-// 00 00000000 00000000 00000000 00   00000000
-//
-// Filenodemap:
-// 00 SPCNODE  DBNODE   00000000 00   00000000
-//
-// RelDir:
-// 00 SPCNODE  DBNODE   00000000 00   00000001 (Postgres never uses relfilenode 0)
+
 //
 // RelBlock:
 // 00 SPCNODE  DBNODE   RELNODE  FORK BLKNUM
 //
-// RelSize:
-// 00 SPCNODE  DBNODE   RELNODE  FORK FFFFFFFF
-//
 // SlruDir:
 // 01 kind     00000000 00000000 00   00000000
 //
@@ -1513,11 +1511,31 @@ static ZERO_PAGE: Bytes = Bytes::from_static(&[0u8; BLCKSZ as usize]);
 // AuxFiles:
 // 03 00000000 00000000 00000000 00   00000002
 //
+// DbDir:
+// 04 00000000 00000000 00000000 00   00000000
+//
+// Filenodemap:
+// 04 SPCNODE  DBNODE   00000000 00   00000000
+//
+// RelDir:
+// 04 SPCNODE  DBNODE   00000000 00   00000001 (Postgres never uses relfilenode 0)
+//
+// RelSize:
+// 04 SPCNODE  DBNODE   RELNODE  FORK FFFFFFFF
 
 //-- Section 01: relation data and metadata
 
+/// Keys above this Key are required to serve a basebackup request
+pub(crate) const BASEBACKUP_CUT: Key = slru_dir_to_key(SlruKind::Clog);
+
+/// Keys aboe this Key are needed to make a logical size calculation
+///
+/// Ensuring that such keys are stored above the main range of user relation
+/// blocks enables much more efficient space management.
+pub(crate) const METADATA_CUT: Key = CONTROLFILE_KEY;
+
 const DBDIR_KEY: Key = Key {
-    field1: 0x00,
+    field1: 0x04,
     field2: 0,
     field3: 0,
     field4: 0,
@@ -1527,14 +1545,14 @@ const DBDIR_KEY: Key = Key {
 
 fn dbdir_key_range(spcnode: Oid, dbnode: Oid) -> Range<Key> {
     Key {
-        field1: 0x00,
+        field1: 0x04,
         field2: spcnode,
         field3: dbnode,
         field4: 0,
         field5: 0,
         field6: 0,
     }..Key {
-        field1: 0x00,
+        field1: 0x04,
         field2: spcnode,
         field3: dbnode,
         field4: 0xffffffff,
@@ -1545,7 +1563,7 @@ fn dbdir_key_range(spcnode: Oid, dbnode: Oid) -> Range<Key> {
 
 fn relmap_file_key(spcnode: Oid, dbnode: Oid) -> Key {
     Key {
-        field1: 0x00,
+        field1: 0x04,
         field2: spcnode,
         field3: dbnode,
         field4: 0,
@@ -1556,7 +1574,7 @@ fn relmap_file_key(spcnode: Oid, dbnode: Oid) -> Key {
 
 fn rel_dir_to_key(spcnode: Oid, dbnode: Oid) -> Key {
     Key {
-        field1: 0x00,
+        field1: 0x04,
         field2: spcnode,
         field3: dbnode,
         field4: 0,
@@ -1578,7 +1596,7 @@ fn rel_block_to_key(rel: RelTag, blknum: BlockNumber) -> Key {
 
 fn rel_size_to_key(rel: RelTag) -> Key {
     Key {
-        field1: 0x00,
+        field1: 0x04,
         field2: rel.spcnode,
         field3: rel.dbnode,
         field4: rel.relnode,
@@ -1607,7 +1625,7 @@ fn rel_key_range(rel: RelTag) -> Range<Key> {
 
 //-- Section 02: SLRUs
 
-fn slru_dir_to_key(kind: SlruKind) -> Key {
+const fn slru_dir_to_key(kind: SlruKind) -> Key {
     Key {
         field1: 0x01,
         field2: match kind {

pageserver/src/tenant.rs

@@ -61,7 +61,6 @@ use self::mgr::TenantsMap;
 use self::remote_timeline_client::RemoteTimelineClient;
 use self::timeline::uninit::TimelineUninitMark;
 use self::timeline::uninit::UninitializedTimeline;
-use self::timeline::EvictionTaskTenantState;
 use self::timeline::TimelineResources;
 use crate::config::PageServerConf;
 use crate::context::{DownloadBehavior, RequestContext};
@@ -252,8 +251,6 @@ pub struct Tenant {
     cached_logical_sizes: tokio::sync::Mutex<HashMap<(TimelineId, Lsn), u64>>,
     cached_synthetic_tenant_size: Arc<AtomicU64>,
 
-    eviction_task_tenant_state: tokio::sync::Mutex<EvictionTaskTenantState>,
-
     pub(crate) delete_progress: Arc<tokio::sync::Mutex<DeleteTenantFlow>>,
 
     // Cancellation token fires when we have entered shutdown().  This is a parent of
@@ -2367,7 +2364,6 @@ impl Tenant {
             state,
             cached_logical_sizes: tokio::sync::Mutex::new(HashMap::new()),
             cached_synthetic_tenant_size: Arc::new(AtomicU64::new(0)),
-            eviction_task_tenant_state: tokio::sync::Mutex::new(EvictionTaskTenantState::default()),
             delete_progress: Arc::new(tokio::sync::Mutex::new(DeleteTenantFlow::default())),
             cancel: CancellationToken::default(),
             gate: Gate::new(format!("Tenant<{tenant_id}>")),

pageserver/src/tenant/storage_layer/layer_desc.rs

@@ -5,7 +5,7 @@ use utils::{
     lsn::Lsn,
 };
 
-use crate::repository::Key;
+use crate::{pgdatadir_mapping::METADATA_CUT, repository::Key};
 
 use super::{DeltaFileName, ImageFileName, LayerFileName};
 
@@ -49,6 +49,20 @@ impl PersistentLayerDesc {
         }
     }
 
+    /// Does this layer consist exclusively of metadata
+    /// content such as dbdir & relation sizes?  This is a
+    /// hint that the layer is likely to be small and should
+    /// not be a candidate for eviction under normal circumstances.
+    pub fn is_metadata_pages(&self) -> bool {
+        self.key_range.start >= METADATA_CUT
+    }
+
+    /// Does this layer consist exclusively of content
+    /// required to serve a basebackup request?
+    pub fn is_basebackup_pages(&self) -> bool {
+        self.key_range.start >= METADATA_CUT
+    }
+
     pub fn short_id(&self) -> impl Display {
         self.filename()
     }

pageserver/src/tenant/timeline.rs

@@ -81,8 +81,6 @@ use crate::task_mgr::TaskKind;
 use crate::ZERO_PAGE;
 
 use self::delete::DeleteTimelineFlow;
-pub(super) use self::eviction_task::EvictionTaskTenantState;
-use self::eviction_task::EvictionTaskTimelineState;
 use self::layer_manager::LayerManager;
 use self::logical_size::LogicalSize;
 use self::walreceiver::{WalReceiver, WalReceiverConf};
@@ -298,8 +296,6 @@ pub struct Timeline {
     /// timeline is being deleted. If 'true', the timeline has already been deleted.
     pub delete_progress: Arc<tokio::sync::Mutex<DeleteTimelineFlow>>,
 
-    eviction_task_timeline_state: tokio::sync::Mutex<EvictionTaskTimelineState>,
-
     /// Barrier to wait before doing initial logical size calculation. Used only during startup.
     initial_logical_size_can_start: Option<completion::Barrier>,
 
@@ -433,7 +429,6 @@ impl std::fmt::Display for PageReconstructError {
 pub enum LogicalSizeCalculationCause {
     Initial,
     ConsumptionMetricsSyntheticSize,
-    EvictionTaskImitation,
     TenantSizeHandler,
 }
 
@@ -1442,9 +1437,6 @@ impl Timeline {
 
                 state,
 
-                eviction_task_timeline_state: tokio::sync::Mutex::new(
-                    EvictionTaskTimelineState::default(),
-                ),
                 delete_progress: Arc::new(tokio::sync::Mutex::new(DeleteTimelineFlow::default())),
 
                 initial_logical_size_can_start,
@@ -1967,9 +1959,6 @@ impl Timeline {
             LogicalSizeCalculationCause::Initial
             | LogicalSizeCalculationCause::ConsumptionMetricsSyntheticSize
             | LogicalSizeCalculationCause::TenantSizeHandler => &self.metrics.logical_size_histo,
-            LogicalSizeCalculationCause::EvictionTaskImitation => {
-                &self.metrics.imitate_logical_size_histo
-            }
         };
         let timer = storage_time_metrics.start_timer();
         let logical_size = self
@@ -2746,18 +2735,18 @@ impl Timeline {
         partition_size: u64,
         ctx: &RequestContext,
     ) -> anyhow::Result<(KeyPartitioning, Lsn)> {
-        {
-            let partitioning_guard = self.partitioning.lock().unwrap();
-            let distance = lsn.0 - partitioning_guard.1 .0;
-            if partitioning_guard.1 != Lsn(0) && distance <= self.repartition_threshold {
-                debug!(
-                    distance,
-                    threshold = self.repartition_threshold,
-                    "no repartitioning needed"
-                );
-                return Ok((partitioning_guard.0.clone(), partitioning_guard.1));
-            }
-        }
+        // {
+        //     let partitioning_guard = self.partitioning.lock().unwrap();
+        //     let distance = lsn.0 - partitioning_guard.1 .0;
+        //     if partitioning_guard.1 != Lsn(0) && distance <= self.repartition_threshold {
+        //         debug!(
+        //             distance,
+        //             threshold = self.repartition_threshold,
+        //             "no repartitioning needed"
+        //         );
+        //         return Ok((partitioning_guard.0.clone(), partitioning_guard.1));
+        //     }
+        // }
         let keyspace = self.collect_keyspace(lsn, ctx).await?;
         let partitioning = keyspace.partition(partition_size);
 
@@ -4285,6 +4274,11 @@ impl Timeline {
             let file_size = l.file_size();
             max_layer_size = max_layer_size.map_or(Some(file_size), |m| Some(m.max(file_size)));
 
+            // Don't evict small layers required to serve a basebackup
+            if l.is_basebackup_pages() {
+                continue;
+            }
+
             let l = guard.get_from_desc(&l);
 
             let l = match l.keep_resident().await {

pageserver/src/tenant/timeline/eviction_task.rs

@@ -14,7 +14,6 @@
 //!
 //! See write-up on restart on-demand download spike: <https://gist.github.com/problame/2265bf7b8dc398be834abfead36c76b5>
 use std::{
-    collections::HashMap,
     ops::ControlFlow,
     sync::Arc,
     time::{Duration, SystemTime},
@@ -22,17 +21,15 @@ use std::{
 
 use tokio::time::Instant;
 use tokio_util::sync::CancellationToken;
-use tracing::{debug, error, info, info_span, instrument, warn, Instrument};
+use tracing::{debug, error, info, instrument, warn};
 
 use crate::{
     context::{DownloadBehavior, RequestContext},
-    pgdatadir_mapping::CollectKeySpaceError,
     task_mgr::{self, TaskKind, BACKGROUND_RUNTIME},
     tenant::{
         config::{EvictionPolicy, EvictionPolicyLayerAccessThreshold},
         tasks::{BackgroundLoopKind, RateLimitError},
         timeline::EvictionError,
-        LogicalSizeCalculationCause, Tenant,
     },
 };
 
@@ -40,16 +37,6 @@ use utils::completion;
 
 use super::Timeline;
 
-#[derive(Default)]
-pub struct EvictionTaskTimelineState {
-    last_layer_access_imitation: Option<tokio::time::Instant>,
-}
-
-#[derive(Default)]
-pub struct EvictionTaskTenantState {
-    last_layer_access_imitation: Option<Instant>,
-}
-
 impl Timeline {
     pub(super) fn launch_eviction_task(
         self: &Arc<Self>,
@@ -178,7 +165,6 @@ impl Timeline {
         //    that were accessed to compute the value in the first place.
         // 3. Invalidate the caches at a period of < p.threshold/2, so that the values
         //    get re-computed from layers, thereby counting towards layer access stats.
-        // 4. Make the eviction task imitate the layer accesses that typically hit caches.
         //
         // We follow approach (4) here because in Neon prod deployment:
         // - page cache is quite small => high churn => low hit rate
@@ -190,10 +176,6 @@ impl Timeline {
         //
         // We should probably move to persistent caches in the future, or avoid
         // having inactive tenants attached to pageserver in the first place.
-        match self.imitate_layer_accesses(p, cancel, ctx).await {
-            ControlFlow::Break(()) => return ControlFlow::Break(()),
-            ControlFlow::Continue(()) => (),
-        }
 
         #[allow(dead_code)]
         #[derive(Debug, Default)]
@@ -215,6 +197,11 @@ impl Timeline {
             let layers = guard.layer_map();
             let mut candidates = Vec::new();
             for hist_layer in layers.iter_historic_layers() {
+                // Don't evict the small layers needed to serve a basebackup request.
+                if hist_layer.is_basebackup_pages() {
+                    continue;
+                }
+
                 let hist_layer = guard.get_from_desc(&hist_layer);
 
                 // guard against eviction while we inspect it; it might be that eviction_task and
@@ -310,170 +297,4 @@ impl Timeline {
         }
         ControlFlow::Continue(())
     }
-
-    #[instrument(skip_all)]
-    async fn imitate_layer_accesses(
-        &self,
-        p: &EvictionPolicyLayerAccessThreshold,
-        cancel: &CancellationToken,
-        ctx: &RequestContext,
-    ) -> ControlFlow<()> {
-        let mut state = self.eviction_task_timeline_state.lock().await;
-
-        // Only do the imitate_layer accesses approximately as often as the threshold.  A little
-        // more frequently, to avoid this period racing with the threshold/period-th eviction iteration.
-        let inter_imitate_period = p.threshold.checked_sub(p.period).unwrap_or(p.threshold);
-
-        match state.last_layer_access_imitation {
-            Some(ts) if ts.elapsed() < inter_imitate_period => { /* no need to run */ }
-            _ => {
-                self.imitate_timeline_cached_layer_accesses(ctx).await;
-                state.last_layer_access_imitation = Some(tokio::time::Instant::now())
-            }
-        }
-        drop(state);
-
-        if cancel.is_cancelled() {
-            return ControlFlow::Break(());
-        }
-
-        // This task is timeline-scoped, but the synthetic size calculation is tenant-scoped.
-        // Make one of the tenant's timelines draw the short straw and run the calculation.
-        // The others wait until the calculation is done so that they take into account the
-        // imitated accesses that the winner made.
-        let tenant = match crate::tenant::mgr::get_tenant(self.tenant_id, true) {
-            Ok(t) => t,
-            Err(_) => {
-                return ControlFlow::Break(());
-            }
-        };
-        let mut state = tenant.eviction_task_tenant_state.lock().await;
-        match state.last_layer_access_imitation {
-            Some(ts) if ts.elapsed() < inter_imitate_period => { /* no need to run */ }
-            _ => {
-                self.imitate_synthetic_size_calculation_worker(&tenant, ctx, cancel)
-                    .await;
-                state.last_layer_access_imitation = Some(tokio::time::Instant::now());
-            }
-        }
-        drop(state);
-
-        if cancel.is_cancelled() {
-            return ControlFlow::Break(());
-        }
-
-        ControlFlow::Continue(())
-    }
-
-    /// Recompute the values which would cause on-demand downloads during restart.
-    #[instrument(skip_all)]
-    async fn imitate_timeline_cached_layer_accesses(&self, ctx: &RequestContext) {
-        let lsn = self.get_last_record_lsn();
-
-        // imitiate on-restart initial logical size
-        let size = self
-            .calculate_logical_size(lsn, LogicalSizeCalculationCause::EvictionTaskImitation, ctx)
-            .instrument(info_span!("calculate_logical_size"))
-            .await;
-
-        match &size {
-            Ok(_size) => {
-                // good, don't log it to avoid confusion
-            }
-            Err(_) => {
-                // we have known issues for which we already log this on consumption metrics,
-                // gc, and compaction. leave logging out for now.
-                //
-                // https://github.com/neondatabase/neon/issues/2539
-            }
-        }
-
-        // imitiate repartiting on first compactation
-        if let Err(e) = self
-            .collect_keyspace(lsn, ctx)
-            .instrument(info_span!("collect_keyspace"))
-            .await
-        {
-            // if this failed, we probably failed logical size because these use the same keys
-            if size.is_err() {
-                // ignore, see above comment
-            } else {
-                match e {
-                    CollectKeySpaceError::Cancelled => {
-                        // Shutting down, ignore
-                    }
-                    err => {
-                        warn!(
-                            "failed to collect keyspace but succeeded in calculating logical size: {err:#}"
-                        );
-                    }
-                }
-            }
-        }
-    }
-
-    // Imitate the synthetic size calculation done by the consumption_metrics module.
-    #[instrument(skip_all)]
-    async fn imitate_synthetic_size_calculation_worker(
-        &self,
-        tenant: &Arc<Tenant>,
-        ctx: &RequestContext,
-        cancel: &CancellationToken,
-    ) {
-        if self.conf.metric_collection_endpoint.is_none() {
-            // We don't start the consumption metrics task if this is not set in the config.
-            // So, no need to imitate the accesses in that case.
-            return;
-        }
-
-        // The consumption metrics are collected on a per-tenant basis, by a single
-        // global background loop.
-        // It limits the number of synthetic size calculations using the global
-        // `concurrent_tenant_size_logical_size_queries` semaphore to not overload
-        // the pageserver. (size calculation is somewhat expensive in terms of CPU and IOs).
-        //
-        // If we used that same semaphore here, then we'd compete for the
-        // same permits, which may impact timeliness of consumption metrics.
-        // That is a no-go, as consumption metrics are much more important
-        // than what we do here.
-        //
-        // So, we have a separate semaphore, initialized to the same
-        // number of permits as the `concurrent_tenant_size_logical_size_queries`.
-        // In the worst, we would have twice the amount of concurrenct size calculations.
-        // But in practice, the `p.threshold` >> `consumption metric interval`, and
-        // we spread out the eviction task using `random_init_delay`.
-        // So, the chance of the worst case is quite low in practice.
-        // It runs as a per-tenant task, but the eviction_task.rs is per-timeline.
-        // So, we must coordinate with other with other eviction tasks of this tenant.
-        let limit = self
-            .conf
-            .eviction_task_immitated_concurrent_logical_size_queries
-            .inner();
-
-        let mut throwaway_cache = HashMap::new();
-        let gather = crate::tenant::size::gather_inputs(
-            tenant,
-            limit,
-            None,
-            &mut throwaway_cache,
-            LogicalSizeCalculationCause::EvictionTaskImitation,
-            ctx,
-        )
-        .instrument(info_span!("gather_inputs"));
-
-        tokio::select! {
-            _ = cancel.cancelled() => {}
-            gather_result = gather => {
-                match gather_result {
-                    Ok(_) => {},
-                    Err(e) => {
-                        // We don't care about the result, but, if it failed, we should log it,
-                        // since consumption metric might be hitting the cached value and
-                        // thus not encountering this error.
-                        warn!("failed to imitate synthetic size calculation accesses: {e:#}")
-                    }
-                }
-           }
-        }
-    }
 }