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pageserver: do big reads to fetch slru segment (#11029)

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## Problem

Each page of the slru segment is fetched individually when it's loaded
on demand.

## Summary of Changes

Use `Timeline::get_vectored` to fetch 16 at a time.
This commit is contained in:
Vlad Lazar
2025-03-05 11:55:55 +00:00
committed by GitHub
parent 38a883118a
commit abae7637d6
1 changed files with 61 additions and 31 deletions
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92
pageserver/src/pgdatadir_mapping.rs
View File

@@ -602,28 +602,36 @@ impl Timeline {
let n_blocks = self
.get_slru_segment_size(kind, segno, Version::Lsn(lsn), ctx)
.await?;
let mut segment = BytesMut::with_capacity(n_blocks as usize * BLCKSZ as usize);
for blkno in 0..n_blocks {
let block = self
.get_slru_page_at_lsn(kind, segno, blkno, lsn, ctx)
.await?;
segment.extend_from_slice(&block[..BLCKSZ as usize]);
}
Ok(segment.freeze())
}
/// Look up given SLRU page version.
pub(crate) async fn get_slru_page_at_lsn(
&self,
kind: SlruKind,
segno: u32,
blknum: BlockNumber,
lsn: Lsn,
ctx: &RequestContext,
) -> Result<Bytes, PageReconstructError> {
assert!(self.tenant_shard_id.is_shard_zero());
let key = slru_block_to_key(kind, segno, blknum);
self.get(key, lsn, ctx).await
let keyspace = KeySpace::single(
slru_block_to_key(kind, segno, 0)..slru_block_to_key(kind, segno, n_blocks),
);
let batches = keyspace.partition(
self.get_shard_identity(),
Timeline::MAX_GET_VECTORED_KEYS * BLCKSZ as u64,
);
let io_concurrency = IoConcurrency::spawn_from_conf(
self.conf,
self.gate
.enter()
.map_err(|_| PageReconstructError::Cancelled)?,
);
let mut segment = BytesMut::with_capacity(n_blocks as usize * BLCKSZ as usize);
for batch in batches.parts {
let blocks = self
.get_vectored(batch, lsn, io_concurrency.clone(), ctx)
.await?;
for (_key, block) in blocks {
let block = block?;
segment.extend_from_slice(&block[..BLCKSZ as usize]);
}
}
Ok(segment.freeze())
}
/// Get size of an SLRU segment
@@ -832,19 +840,41 @@ impl Timeline {
let nblocks = self
.get_slru_segment_size(SlruKind::Clog, segno, Version::Lsn(probe_lsn), ctx)
.await?;
for blknum in (0..nblocks).rev() {
let clog_page = self
.get_slru_page_at_lsn(SlruKind::Clog, segno, blknum, probe_lsn, ctx)
let keyspace = KeySpace::single(
slru_block_to_key(SlruKind::Clog, segno, 0)
..slru_block_to_key(SlruKind::Clog, segno, nblocks),
);
let batches = keyspace.partition(
self.get_shard_identity(),
Timeline::MAX_GET_VECTORED_KEYS * BLCKSZ as u64,
);
let io_concurrency = IoConcurrency::spawn_from_conf(
self.conf,
self.gate
.enter()
.map_err(|_| PageReconstructError::Cancelled)?,
);
for batch in batches.parts.into_iter().rev() {
let blocks = self
.get_vectored(batch, probe_lsn, io_concurrency.clone(), ctx)
.await?;
if clog_page.len() == BLCKSZ as usize + 8 {
let mut timestamp_bytes = [0u8; 8];
timestamp_bytes.copy_from_slice(&clog_page[BLCKSZ as usize..]);
let timestamp = TimestampTz::from_be_bytes(timestamp_bytes);
for (_key, clog_page) in blocks.into_iter().rev() {
let clog_page = clog_page?;
match f(timestamp) {
ControlFlow::Break(b) => return Ok(b),
ControlFlow::Continue(()) => (),
if clog_page.len() == BLCKSZ as usize + 8 {
let mut timestamp_bytes = [0u8; 8];
timestamp_bytes.copy_from_slice(&clog_page[BLCKSZ as usize..]);
let timestamp = TimestampTz::from_be_bytes(timestamp_bytes);
match f(timestamp) {
ControlFlow::Break(b) => return Ok(b),
ControlFlow::Continue(()) => (),
}
}
}
}