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: 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>, Antonin Houska <ah@cybertec.at>
Date: 2025-03-29T13:41:43Z
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 aio: Fix reference to outdated name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 Fri, Mar 28, 2025 at 11:35:23PM -0400, Andres Freund wrote:
> The number of combinations is annoyingly large. It's e.g. plausible to use
> ignore_checksum_failure=on and zero_damaged_pages=on at the same time for
> recovery.

That's intricate indeed.

> But I finally got to a point where the code ends up readable, without undue
> duplication.  It would, leaving some nasty hack aside, require a
> errhint_internal() - but I can't imagine a reason against introducing that,
> given we have it for the errmsg and errhint.

Introducing that is fine.

> Here's the relevant code:
> 
> 	/*
> 	 * Treat a read that had both zeroed buffers *and* ignored checksums as a
> 	 * special case, it's too irregular to be emitted the same way as the other
> 	 * cases.
> 	 */
> 	if (zeroed_any && ignored_any)
> 	{
> 		Assert(zeroed_any && ignored_any);
> 		Assert(nblocks > 1);	/* same block can't be both zeroed and ignored */
> 		Assert(result.status != PGAIO_RS_ERROR);
> 		affected_count = zeroed_or_error_count;
> 
> 		ereport(elevel,
> 				errcode(ERRCODE_DATA_CORRUPTED),
> 				errmsg("zeroing %u pages and ignoring %u checksum failures among blocks %u..%u of relation %s",
> 					   affected_count, checkfail_count, first, last, rpath.str),

Translation stumbles on this one, because each of the first two %u are
plural-sensitive.  I'd do one of:

- Call ereport() twice, once for zeroed pages and once for ignored checksums.
  Since elevel <= ERROR here, that doesn't lose the second call.

- s/pages/page(s)/ like msgid "There are %d other session(s) and %d prepared
  transaction(s) using the database."

- Something more like the style of VACUUM VERBOSE, e.g. "INTRO_TEXT: %u
  zeroed, %u checksums ignored".  I've not written INTRO_TEXT, and this
  doesn't really resolve pluralization.  Probably don't use this option.

> 				affected_count > 1 ?
> 				errdetail("Block %u held first zeroed page.",
> 						  first + first_off) : 0,
> 				errhint("See server log for details about the other %u invalid blocks.",
> 						affected_count + checkfail_count - 1));
> 		return;
> 	}
> 
> 	/*
> 	 * The other messages are highly repetitive. To avoid duplicating a long
> 	 * and complicated ereport(), gather the translated format strings
> 	 * separately and then do one common ereport.
> 	 */
> 	if (result.status == PGAIO_RS_ERROR)
> 	{
> 		Assert(!zeroed_any);	/* can't have invalid pages when zeroing them */
> 		affected_count = zeroed_or_error_count;
> 		msg_one = _("invalid page in block %u of relation %s");
> 		msg_mult = _("%u invalid pages among blocks %u..%u of relation %s");
> 		det_mult = _("Block %u held first invalid page.");
> 		hint_mult = _("See server log for the other %u invalid blocks.");

For each hint_mult, we would usually use ngettext() instead of _().  (Would be
errhint_plural() if not separated from its ereport().)  Alternatively,
s/blocks/block(s)/ is fine.

> 	}
> 	else if (zeroed_any && !ignored_any)
> 	{
> 		affected_count = zeroed_or_error_count;
> 		msg_one = _("invalid page in block %u of relation %s; zeroing out page");
> 		msg_mult = _("zeroing out %u invalid pages among blocks %u..%u of relation %s");
> 		det_mult = _("Block %u held first zeroed page.");
> 		hint_mult = _("See server log for the other %u zeroed blocks.");
> 	}
> 	else if (!zeroed_any && ignored_any)
> 	{
> 		affected_count = checkfail_count;
> 		msg_one = _("ignoring checksum failure in block %u of relation %s");
> 		msg_mult = _("ignoring %u checksum failures among blocks %u..%u of relation %s");
> 		det_mult = _("Block %u held first ignored page.");
> 		hint_mult = _("See server log for the other %u ignored blocks.");
> 	}
> 	else
> 		pg_unreachable();
> 
> 	ereport(elevel,
> 			errcode(ERRCODE_DATA_CORRUPTED),
> 			affected_count == 1 ?
> 			errmsg_internal(msg_one, first + first_off, rpath.str) :
> 			errmsg_internal(msg_mult, affected_count, first, last, rpath.str),
> 			affected_count > 1 ? errdetail_internal(det_mult, first + first_off) : 0,
> 			affected_count > 1 ? errhint_internal(hint_mult, affected_count - 1) : 0);
> 
> Does that approach make sense?

Yes.

> What do you think about using
>   "zeroing invalid page in block %u of relation %s"
> instead of
>   "invalid page in block %u of relation %s; zeroing out page"

I like the replacement.  It moves the important part to the front, and it's
shorter.

> I thought about instead translating "ignoring", "ignored", "zeroing",
> "zeroed", etc separately, but I have doubts about how well that would actually
> translate.

Agreed, I wouldn't have high hopes for that.  An approach like that would
probably need messages that separate the independently-translated part
grammatically, e.g.:

  /* last %s is translation of "ignore" or "zero-fill" */
  "invalid page in block %u of relation %s; resolved by method \"%s\""

(Again, I'm not recommending that.)