diff options
| author | Andres Freund <andres@anarazel.de> | 2024-10-08 11:37:45 -0400 |
|---|---|---|
| committer | Andres Freund <andres@anarazel.de> | 2024-10-08 11:37:45 -0400 |
| commit | 755a4c10d19dbe432a1860cced914c570ff3becc (patch) | |
| tree | 7e803b760da946a32987cac5c2b0d21b5b9a9a32 /src/include | |
| parent | 488f826c729bd570c36df369fa8ac90c9a5a1b46 (diff) | |
bufmgr/smgr: Don't cross segment boundaries in StartReadBuffers()
With real AIO it doesn't make sense to cross segment boundaries with one
IO. Add smgrmaxcombine() to allow upper layers to query which buffers can be
merged.
We could continue to cross segment boundaries when not using AIO, but it
doesn't really make sense, because md.c will never be able to perform the read
across the segment boundary in one system call. Which means we'll mark more
buffers as undergoing IO than really makes sense - if another backend desires
to read the same blocks, it'll be blocked longer than necessary. So it seems
better to just never cross the boundary.
Reviewed-by: Heikki Linnakangas <hlinnaka@iki.fi>
Reviewed-by: Noah Misch <noah@leadboat.com>
Discussion: https://postgr.es/m/1f6b50a7-38ef-4d87-8246-786d39f46ab9@iki.fi
Diffstat (limited to 'src/include')
| -rw-r--r-- | src/include/storage/md.h | 2 | ||||
| -rw-r--r-- | src/include/storage/smgr.h | 2 |
2 files changed, 4 insertions, 0 deletions
diff --git a/src/include/storage/md.h b/src/include/storage/md.h index 620f10abdeb..b72293c79a5 100644 --- a/src/include/storage/md.h +++ b/src/include/storage/md.h @@ -32,6 +32,8 @@ extern void mdzeroextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks, bool skipFsync); extern bool mdprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks); +extern uint32 mdmaxcombine(SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum); extern void mdreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, void **buffers, BlockNumber nblocks); extern void mdwritev(SMgrRelation reln, ForkNumber forknum, diff --git a/src/include/storage/smgr.h b/src/include/storage/smgr.h index e15b20a566a..899d0d681c5 100644 --- a/src/include/storage/smgr.h +++ b/src/include/storage/smgr.h @@ -92,6 +92,8 @@ extern void smgrzeroextend(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks, bool skipFsync); extern bool smgrprefetch(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, int nblocks); +extern uint32 smgrmaxcombine(SMgrRelation reln, ForkNumber forknum, + BlockNumber blocknum); extern void smgrreadv(SMgrRelation reln, ForkNumber forknum, BlockNumber blocknum, void **buffers, BlockNumber nblocks); |