Horton

Re: AIO v2.5

Andres Freund <andres@anarazel.de>

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From: Andres Freund <andres@anarazel.de>
To: Noah Misch <noah@leadboat.com>
Cc: Thomas Munro <thomas.munro@gmail.com>, Antonin Houska <ah@cybertec.at>, pgsql-hackers@postgresql.org, Heikki Linnakangas <hlinnaka@iki.fi>, Robert Haas <robertmhaas@gmail.com>, Jakub Wartak <jakub.wartak@enterprisedb.com>, Jelte Fennema-Nio <postgres@jeltef.nl>
Date: 2025-03-25T20:56:53Z
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 aio: Fix reference to outdated name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

Attachments

Hi,

On 2025-03-25 13:18:50 -0700, Noah Misch wrote:
> On Tue, Mar 25, 2025 at 04:07:35PM -0400, Andres Freund wrote:
> > On 2025-03-25 12:39:56 -0700, Noah Misch wrote:
> > > On Tue, Mar 25, 2025 at 02:58:37PM -0400, Andres Freund wrote:
> > > > There are 2 1/2 ways around this:
> > > > 
> > > > 1) Stop using IOSQE_ASYNC heuristic
> > > > 2a) Wait for all in-flight IOs when any FD gets closed
> > > > 2b) Wait for all in-flight IOs using FD when it gets closed
> > > > 
> > > > Given that we have clear evidence that io_uring doesn't completely support
> > > > closing FDs while IOs are in flight, be it a bug or intentional, it seems
> > > > clearly better to go for 2a or 2b.
> > > 
> > > Agreed.  If a workload spends significant time on fd.c closing files, I
> > > suspect that workload already won't have impressive benchmark numbers.
> > > Performance-seeking workloads will already want to tune FD usage high enough
> > > to keep FDs long-lived.  So (1) clearly loses, and neither (2a) nor (2b)
> > > clearly beats the other.  I'd try (2b) first but, if complicated, quickly
> > > abandon it in favor of (2a).  What other considerations could be important?
> > 
> > The only other consideration I can think of is whether this should happen for
> > all io_methods or not.
> 
> Either way is fine, I think.

Here's a draft incremental patch (attached as a .fixup to avoid triggering
cfbot) implementing 2b).


> > I'm inclined to do it via a bool in IoMethodOps, but I guess one could argue
> > it's a bit weird to have a bool in a struct called *Ops.
> 
> That wouldn't bother me.  IndexAmRoutine has many bools, and "Ops" is
> basically a synonym of "Routine".

Cool. Done that way.

The repeated-iteration approach taken in pgaio_closing_fd() isn't the
prettiest, but it's hard to to imagine that ever being a noticeable.


This survives a testrun where I use your torture patch and where I force all
IOs to use ASYNC. Previously that did not get very far.  I also did verify
that, if I allow a small number of FDs, we do not wrongly wait for all IOs.

Greetings,

Andres Freund