Horton

Re: AIO v2.5

Noah Misch <noah@leadboat.com>

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From: Noah Misch <noah@leadboat.com>
To: Andres Freund <andres@anarazel.de>
Cc: Antonin Houska <ah@cybertec.at>, pgsql-hackers@postgresql.org, Thomas Munro <thomas.munro@gmail.com>, Heikki Linnakangas <hlinnaka@iki.fi>, Robert Haas <robertmhaas@gmail.com>, Jakub Wartak <jakub.wartak@enterprisedb.com>, Jelte Fennema-Nio <postgres@jeltef.nl>
Date: 2025-03-25T16:15:43Z
Lists: pgsql-hackers

Commits

Same data as JSON: GET /api/v1/messages/:b64id/commits the thread's linked commits as JSON, with link sources. API reference →

  1. aio: Fix assertion, clarify README

  2. aio: Fix reference to outdated name

  3. aio: Fix possible state confusions due to interrupt processing

  4. aio: Improve debug logging around waiting for IOs

  5. aio: Fix crash potential for pg_aios views due to late state update

  6. Increase BAS_BULKREAD based on effective_io_concurrency

  7. localbuf: Add Valgrind buffer access instrumentation

  8. aio: Make AIO more compatible with valgrind

  9. aio: Avoid spurious coverity warning

  10. tests: Fix incompatibility of test_aio with *_FORCE_RELEASE

  11. tests: Cope with WARNINGs during failed CREATE DB on windows

  12. aio: Add errcontext for processing I/Os for another backend

  13. aio: Add README.md explaining higher level design

  14. aio: Minor comment improvements

  15. aio: Add test_aio module

  16. aio: Add pg_aios view

  17. docs: Add acronym and glossary entries for I/O and AIO

  18. Enable IO concurrency on all systems

  19. read_stream: Introduce and use optional batchmode support

  20. docs: Reframe track_io_timing related docs as wait time

  21. bufmgr: Use AIO in StartReadBuffers()

  22. bufmgr: Implement AIO read support

  23. aio: Add WARNING result status

  24. Let caller of PageIsVerified() control ignore_checksum_failure

  25. pgstat: Allow checksum errors to be reported in critical sections

  26. Add errhint_internal()

  27. localbuf: Track pincount in BufferDesc as well

  28. aio, bufmgr: Comment fixes/improvements

  29. Fix mis-attribution of checksum failure stats to the wrong database

  30. aio: Implement support for reads in smgr/md/fd

  31. aio: Add io_method=io_uring

  32. aio: Add liburing dependency

  33. aio: Rename pgaio_io_prep_* to pgaio_io_start_*

  34. aio: Pass result of local callbacks to ->report_return

  35. aio: Be more paranoid about interrupts

  36. Redefine max_files_per_process to control additionally opened files

  37. aio: Change prefix of PgAioResultStatus values to PGAIO_RS_

  38. bufmgr: Improve stats when a buffer is read in concurrently

  39. aio: Add io_method=worker

  40. aio: Infrastructure for io_method=worker

  41. aio: Add core asynchronous I/O infrastructure

  42. aio: Basic subsystem initialization

  43. tests: Expand temp table tests to some pin related matters

  44. localbuf: Introduce FlushLocalBuffer()

  45. localbuf: Introduce TerminateLocalBufferIO()

  46. localbuf: Fix dangerous coding pattern in GetLocalVictimBuffer()

  47. localbuf: Introduce StartLocalBufferIO()

  48. localbuf: Introduce InvalidateLocalBuffer()

  49. Allow lwlocks to be disowned

  50. Make jsonb casts to scalar types translate JSON null to SQL NULL.

  51. bufmgr/smgr: Don't cross segment boundaries in StartReadBuffers()

  52. Use aux process resource owner in walsender

  53. bufmgr: Return early in ScheduleBufferTagForWriteback() if fsync=off

On Tue, Mar 25, 2025 at 11:57:58AM -0400, Andres Freund wrote:
> On 2025-03-25 07:11:20 -0700, Noah Misch wrote:
> > On Mon, Mar 24, 2025 at 10:52:19PM -0400, Andres Freund wrote:
> > > If we want to implement it, I think we could introduce PGAIO_RS_WARN, which
> > > then could tell the stager to issue the WARNING. It would add a bit of
> > > distributed cost, both to callbacks and users of AIO, but it might not be too
> > > bad.
> 
> FWIW, I prototyped this, it's not hard.
> 
> But it can't replace the current WARNING with 100% fidelity: If we read 60
> blocks in a single smgrreadv, we today would would emit 60 WARNINGs.  But we
> can't encode that many block offset in single PgAioResult, there's not enough
> space, and enlarging it far enough doesn't seem to make sense either.
> 
> 
> What we *could* do is to emit one WARNING for each bufmgr.c smgrstartreadv(),
> with that warning saying that there were N zeroed blocks in a read from block
> N to block Y and a HINT saying that there are more details in the server log.

Sounds fine.

> > Another thought on complete_shared running on other backends: I wonder if we
> > should push an ErrorContextCallback that adds "CONTEXT: completing I/O of
> > other process" or similar, so people wonder less about how "SELECT FROM a" led
> > to a log message about IO on table "b".
> 
> I've been wondering about that as well, and yes, we probably should.
> 
> I'd add the pid of the backend that started the IO to the message - although
> need to check whether we're trying to keep PIDs of other processes from
> unprivileged users.

We don't.

> I think we probably should add a similar, but not equivalent, context in io
> workers. Maybe "I/O worker executing I/O on behalf of process %d".

Sounds good.