Files
neon/pageserver/benches/bench_ingest.rs
Yuchen Liang 49d5e56c08 pageserver: use direct IO for delta and image layer reads (#9326)
Part of #8130 

## Problem

Pageserver previously goes through the kernel page cache for all the
IOs. The kernel page cache makes light-loaded pageserver have deceptive
fast performance. Using direct IO would offer predictable latencies of
our virtual file IO operations.

In particular for reads, the data pages also have an extremely low
temporal locality because the most frequently accessed pages are cached
on the compute side.

## Summary of changes

This PR enables pageserver to use direct IO for delta layer and image
layer reads. We can ship them separately because these layers are
write-once, read-many, so we will not be mixing buffered IO with direct
IO.

- implement `IoBufferMut`, an buffer type with aligned allocation
(currently set to 512).
- use `IoBufferMut` at all places we are doing reads on image + delta
layers.
- leverage Rust type system and use `IoBufAlignedMut` marker trait to
guarantee that the input buffers for the IO operations are aligned.
- page cache allocation is also made aligned.

_* in-memory layer reads and the write path will be shipped separately._

## Testing

Integration test suite run with O_DIRECT enabled:
https://github.com/neondatabase/neon/pull/9350

## Performance

We evaluated performance based on the `get-page-at-latest-lsn`
benchmark. The results demonstrate a decrease in the number of IOps, no
sigificant change in the latency mean, and an slight improvement on the
p99.9 and p99.99 latencies.


[Benchmark](https://www.notion.so/neondatabase/Benchmark-O_DIRECT-for-image-and-delta-layers-2024-10-01-112f189e00478092a195ea5a0137e706?pvs=4)

## Rollout

We will add `virtual_file_io_mode=direct` region by region to enable
direct IO on image + delta layers.

Signed-off-by: Yuchen Liang <yuchen@neon.tech>
2024-10-21 11:01:25 -04:00

259 lines
8.2 KiB
Rust

use std::{env, num::NonZeroUsize};
use bytes::Bytes;
use camino::Utf8PathBuf;
use criterion::{criterion_group, criterion_main, Criterion};
use pageserver::{
config::PageServerConf,
context::{DownloadBehavior, RequestContext},
l0_flush::{L0FlushConfig, L0FlushGlobalState},
page_cache,
repository::Value,
task_mgr::TaskKind,
tenant::storage_layer::inmemory_layer::SerializedBatch,
tenant::storage_layer::InMemoryLayer,
virtual_file,
};
use pageserver_api::{key::Key, shard::TenantShardId};
use utils::{
bin_ser::BeSer,
id::{TenantId, TimelineId},
};
// A very cheap hash for generating non-sequential keys.
fn murmurhash32(mut h: u32) -> u32 {
h ^= h >> 16;
h = h.wrapping_mul(0x85ebca6b);
h ^= h >> 13;
h = h.wrapping_mul(0xc2b2ae35);
h ^= h >> 16;
h
}
enum KeyLayout {
/// Sequential unique keys
Sequential,
/// Random unique keys
Random,
/// Random keys, but only use the bits from the mask of them
RandomReuse(u32),
}
enum WriteDelta {
Yes,
No,
}
async fn ingest(
conf: &'static PageServerConf,
put_size: usize,
put_count: usize,
key_layout: KeyLayout,
write_delta: WriteDelta,
) -> anyhow::Result<()> {
let mut lsn = utils::lsn::Lsn(1000);
let mut key = Key::from_i128(0x0);
let timeline_id = TimelineId::generate();
let tenant_id = TenantId::generate();
let tenant_shard_id = TenantShardId::unsharded(tenant_id);
tokio::fs::create_dir_all(conf.timeline_path(&tenant_shard_id, &timeline_id)).await?;
let ctx = RequestContext::new(TaskKind::DebugTool, DownloadBehavior::Error);
let gate = utils::sync::gate::Gate::default();
let entered = gate.enter().unwrap();
let layer =
InMemoryLayer::create(conf, timeline_id, tenant_shard_id, lsn, entered, &ctx).await?;
let data = Value::Image(Bytes::from(vec![0u8; put_size]));
let data_ser_size = data.serialized_size().unwrap() as usize;
let ctx = RequestContext::new(
pageserver::task_mgr::TaskKind::WalReceiverConnectionHandler,
pageserver::context::DownloadBehavior::Download,
);
const BATCH_SIZE: usize = 16;
let mut batch = Vec::new();
for i in 0..put_count {
lsn += put_size as u64;
// Generate lots of keys within a single relation, which simulates the typical bulk ingest case: people
// usually care the most about write performance when they're blasting a huge batch of data into a huge table.
match key_layout {
KeyLayout::Sequential => {
// Use sequential order to illustrate the experience a user is likely to have
// when ingesting bulk data.
key.field6 = i as u32;
}
KeyLayout::Random => {
// Use random-order keys to avoid giving a false advantage to data structures that are
// faster when inserting on the end.
key.field6 = murmurhash32(i as u32);
}
KeyLayout::RandomReuse(mask) => {
// Use low bits only, to limit cardinality
key.field6 = murmurhash32(i as u32) & mask;
}
}
batch.push((key.to_compact(), lsn, data_ser_size, data.clone()));
if batch.len() >= BATCH_SIZE {
let this_batch = std::mem::take(&mut batch);
let serialized = SerializedBatch::from_values(this_batch).unwrap();
layer.put_batch(serialized, &ctx).await?;
}
}
if !batch.is_empty() {
let this_batch = std::mem::take(&mut batch);
let serialized = SerializedBatch::from_values(this_batch).unwrap();
layer.put_batch(serialized, &ctx).await?;
}
layer.freeze(lsn + 1).await;
if matches!(write_delta, WriteDelta::Yes) {
let l0_flush_state = L0FlushGlobalState::new(L0FlushConfig::Direct {
max_concurrency: NonZeroUsize::new(1).unwrap(),
});
let (_desc, path) = layer
.write_to_disk(&ctx, None, l0_flush_state.inner())
.await?
.unwrap();
tokio::fs::remove_file(path).await?;
}
Ok(())
}
/// Wrapper to instantiate a tokio runtime
fn ingest_main(
conf: &'static PageServerConf,
put_size: usize,
put_count: usize,
key_layout: KeyLayout,
write_delta: WriteDelta,
) {
let runtime = tokio::runtime::Builder::new_current_thread()
.enable_all()
.build()
.unwrap();
runtime.block_on(async move {
let r = ingest(conf, put_size, put_count, key_layout, write_delta).await;
if let Err(e) = r {
panic!("{e:?}");
}
});
}
/// Declare a series of benchmarks for the Pageserver's ingest write path.
///
/// This benchmark does not include WAL decode: it starts at InMemoryLayer::put_value, and ends either
/// at freezing the ephemeral layer, or writing the ephemeral layer out to an L0 (depending on whether WriteDelta is set).
///
/// Genuine disk I/O is used, so expect results to differ depending on storage. However, when running on
/// a fast disk, CPU is the bottleneck at time of writing.
fn criterion_benchmark(c: &mut Criterion) {
let temp_dir_parent: Utf8PathBuf = env::current_dir().unwrap().try_into().unwrap();
let temp_dir = camino_tempfile::tempdir_in(temp_dir_parent).unwrap();
eprintln!("Data directory: {}", temp_dir.path());
let conf: &'static PageServerConf = Box::leak(Box::new(
pageserver::config::PageServerConf::dummy_conf(temp_dir.path().to_path_buf()),
));
virtual_file::init(
16384,
virtual_file::io_engine_for_bench(),
conf.virtual_file_io_mode,
);
page_cache::init(conf.page_cache_size);
{
let mut group = c.benchmark_group("ingest-small-values");
let put_size = 100usize;
let put_count = 128 * 1024 * 1024 / put_size;
group.throughput(criterion::Throughput::Bytes((put_size * put_count) as u64));
group.sample_size(10);
group.bench_function("ingest 128MB/100b seq", |b| {
b.iter(|| {
ingest_main(
conf,
put_size,
put_count,
KeyLayout::Sequential,
WriteDelta::Yes,
)
})
});
group.bench_function("ingest 128MB/100b rand", |b| {
b.iter(|| {
ingest_main(
conf,
put_size,
put_count,
KeyLayout::Random,
WriteDelta::Yes,
)
})
});
group.bench_function("ingest 128MB/100b rand-1024keys", |b| {
b.iter(|| {
ingest_main(
conf,
put_size,
put_count,
KeyLayout::RandomReuse(0x3ff),
WriteDelta::Yes,
)
})
});
group.bench_function("ingest 128MB/100b seq, no delta", |b| {
b.iter(|| {
ingest_main(
conf,
put_size,
put_count,
KeyLayout::Sequential,
WriteDelta::No,
)
})
});
}
{
let mut group = c.benchmark_group("ingest-big-values");
let put_size = 8192usize;
let put_count = 128 * 1024 * 1024 / put_size;
group.throughput(criterion::Throughput::Bytes((put_size * put_count) as u64));
group.sample_size(10);
group.bench_function("ingest 128MB/8k seq", |b| {
b.iter(|| {
ingest_main(
conf,
put_size,
put_count,
KeyLayout::Sequential,
WriteDelta::Yes,
)
})
});
group.bench_function("ingest 128MB/8k seq, no delta", |b| {
b.iter(|| {
ingest_main(
conf,
put_size,
put_count,
KeyLayout::Sequential,
WriteDelta::No,
)
})
});
}
}
criterion_group!(benches, criterion_benchmark);
criterion_main!(benches);