Horton

Re: AIO v2.2

Heikki Linnakangas <hlinnaka@iki.fi>

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From: Heikki Linnakangas <hlinnaka@iki.fi>
To: Andres Freund <andres@anarazel.de>, pgsql-hackers@postgresql.org
Date: 2025-01-07T16:08:51Z
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 aio: Fix reference to outdated name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 LWLockDisown():

> +/*
> + * Stop treating lock as held by current backend.
> + *
> + * After calling this function it's the callers responsibility to ensure that
> + * the lock gets released, even in case of an error. This only is desirable if
> + * the lock is going to be released in a different process than the process
> + * that acquired it.
> + *
> + * Returns the mode in which the lock was held by the current backend.

Returning the lock mode feels a bit ad hoc..

> + * NB: This will leave lock->owner pointing to the current backend (if
> + * LOCK_DEBUG is set). We could add a separate flag indicating that, but it
> + * doesn't really seem worth it.

Hmm. I won't insist, but I feel it probably would be worth it. This is 
only in LOCK_DEBUG mode so there's no performance penalty in non-debug 
builds, and when you do compile with LOCK_DEBUG you probably appreciate 
any extra information.

> + * NB: This does not call RESUME_INTERRUPTS(), but leaves that responsibility
> + * of the caller.
> + */

That feels weird. The only caller outside lwlock.c does call 
RESUME_INTERRUPTS() immediately.

Perhaps it'd make for a better external interface if LWLockDisown() did 
call RESUME_INTERRUPTS(), and there was a separate internal version that 
didn't. And it might make more sense for the external version to return 
'void' while we're at it. Returning a value that the caller ignores is 
harmless, of course, but it feels a bit weird. It makes you wonder what 
you're supposed to do with it.

> +	{
> +		{"io_method", PGC_POSTMASTER, RESOURCES_MEM,
> +			gettext_noop("Selects the method of asynchronous I/O to use."),
> +			NULL
> +		},
> +		&io_method,
> +		DEFAULT_IO_METHOD, io_method_options,
> +		NULL, assign_io_method, NULL
> +	},
> +

The description is a bit funny because synchronous I/O is one of the 
possible methods.

-- 
Heikki Linnakangas
Neon (https://neon.tech)