Horton

Re: AIO v2.0

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: 陈宗志 <baotiao@gmail.com>
Cc: Heikki Linnakangas <hlinnaka@iki.fi>, pgsql-hackers@postgresql.org
Date: 2024-09-06T19:47:35Z
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 aio: Fix reference to outdated name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 2024-09-05 01:37:34 +0800, 陈宗志 wrote:
> I hope there can be a high-level design document that includes a
> description, high-level architecture, and low-level design.
> This way, others can also participate in reviewing the code.

Yep, that was already on my todo list. The version I just posted includes
that.


> For example, which paths were modified in the AIO module?
> Is it the path for writing WAL logs, or the path for flushing pages, etc.?

I don't think it's good to document this in a design document - that's just
bound to get out of date.

For now the patchset causes AIO to be used for

1) all users of read_stream.h, e.g. sequential scans

2) bgwriter / checkpointer, mainly to have way to exercise the write path. As
   mentioned in my email upthread, the code for that is in a somewhat rough
   shape as Thomas Munro is working on a more general abstraction for some of
   this.

The earlier patchset added a lot more AIO uses because I needed to know all
the design constraints. It e.g. added AIO use in WAL. While that allowed me to
learn a lot, it's not something that makes sense to continue working on for
now, as it requires a lot of work that's independent of AIO.  Thus I am
focusing on the above users for now.


> Also, I recommend keeping this patch as small as possible.

Yep. That's my goal (as mentioned upthread).


> For example, the first step could be to introduce libaio only, without
> considering io_uring, as that would make it too complex.

Currently the patchset doesn't contain libaio support and I am not planning to
work on using libaio. Nor do I think it makes sense for anybody else to do so
- libaio doesn't work for buffered IO, making it imo not particularly useful
for us.

The io_uring specific code isn't particularly complex / large compared to the
main AIO infrastructure.

Greetings,

Andres Freund