Horton

Re: AIO v2.3

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Thomas Munro <thomas.munro@gmail.com>
Cc: pgsql-hackers@postgresql.org, Heikki Linnakangas <hlinnaka@iki.fi>, Robert Haas <robertmhaas@gmail.com>, Noah Misch <noah@leadboat.com>, Jakub Wartak <jakub.wartak@enterprisedb.com>
Date: 2025-02-11T21:43:22Z
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 aio: Fix reference to outdated name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

Hi,

On 2025-02-11 11:48:38 +1300, Thomas Munro wrote:
> Would the API be better like this?:  When you want to create a batch
> of I/Os submitted together, you wrap the work in pgaio_begin_batch()
> and pgaio_submit_batch(), eg the loop in read_stream_lookahead().

One annoying detail is that an API like this would afaict need resowner
support or something along those lines (e.g. xact callbacks plus code in each
aux process' sigsetjmp() block). Otherwise I don't know how we would ensure
that the "batch-is-in-progress" flag/counter would get reset.

Alternatively we could make pgaio_batch_begin() basically start a critical
section, but that doesn't seem like a good idea, because too much that needs
to happen around buffered IO isn't compatible with critical sections.


Does anybody see a need for batches to be nested? I'm inclined to think that
that would be indicative of bugs and should therefore error/assert out.


One way we could avoid the need for a mechanism to reset-batch-in-progress
would be to make batch submission controlled by a flag on the IO. Something
like
    pgaio_io_set_flag(ioh, PGAIO_HF_BATCH_SUBMIT)

IFF PGAIO_HF_BATCH_SUBMIT is set, the IOs would need to be explicitly
submitted using something like the existing
    pgaio_submit_staged();
(although renaming it to something with batch in the name might be
appropriate)

That way there's no explicit "we are in a batch" state that needs to be reset
in case of errors.

Greetings,

Andres Freund