Horton

Re: AIO v2.5

Alexander Lakhin <exclusion@gmail.com>

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From: Alexander Lakhin <exclusion@gmail.com>
To: Andres Freund <andres@anarazel.de>
Cc: Noah Misch <noah@leadboat.com>, 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: 2025-04-13T06:00:01Z
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 aio: Fix reference to outdated name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

Hello Andres,

07.04.2025 22:10, Alexander Lakhin wrote:
>> I ran it for a while in a VM, it hasn't triggered yet. Neither on xfs nor on
>> tmpfs.
>
> Before sharing the script I tested it on two my machines, but I had
> anticipated that the error can be hard to reproduce. Will try to reduce
> the reproducer...

I've managed to reduce it to the following:
ulimit -n 4096

echo "
fsync = off
autovacuum = off

checkpoint_timeout = 30s

io_max_concurrency = 10
io_method = io_uring
" >> $PGDATA/postgresql.conf

pg_ctl -l server.log start

for i in `seq 1000`; do
   numjobs=$((20 + $RANDOM % 60))
   echo "iteration $i (jobs: $numjobs)"
   date
   for ((j=1;j<=numjobs;j++)); do
     (
       createdb db$j;
       for ((n=1;n<=50;n++)); do
         cat << EOF | psql -d db$j -a >>/dev/null 2>&1
DROP TABLE IF EXISTS tenk1;
CREATE TABLE tenk1 (
     unique1     int4,
     unique2     int4,
     two         int4,
     four        int4,
     ten         int4,
     twenty      int4,
     hundred     int4,
     thousand    int4,
     twothousand int4,
     fivethous   int4,
     tenthous    int4,
     odd         int4,
     even        int4,
     stringu1    name,
     stringu2    name,
     string4     name
);
COPY tenk1 FROM '.../src/test/regress/data/tenk.data';
EOF
       done;
     ) &
   done
   wait

   for ((j=1;j<=numjobs;j++)); do dropdb db$j & done
   wait
   grep -A3 -E '(ERROR|could not read blocks )' server.log && break;
done

pg_ctl stop

It fails for me as below:
iteration 13 (jobs: 25)
Sun Apr 13 05:31:47 AM UTC 2025
iteration 14 (jobs: 67)
Sun Apr 13 05:31:50 AM UTC 2025
dropdb: error: database removal failed: ERROR:  could not read blocks 0..0 in file "global/1213": Operation canceled
2025-04-13 05:31:58.930 UTC [1153451] LOG:  could not read blocks 0..0 in file "global/1213": Operation canceled
2025-04-13 05:31:58.930 UTC [1153451] CONTEXT:  completing I/O on behalf of process 1153456
2025-04-13 05:31:58.930 UTC [1153451] STATEMENT:  DROP DATABASE db5;
2025-04-13 05:31:58.930 UTC [1153456] ERROR:  could not read blocks 0..0 in file "global/1213": Operation canceled
2025-04-13 05:31:58.930 UTC [1153456] STATEMENT:  DROP DATABASE db6;
2025-04-13 05:31:58.931 UTC [1034758] LOG:  checkpoint complete: wrote 3 buffers (0.0%), wrote 0 SLRU buffers; 0 WAL 
file(s) added, 0 removed, 0 recycled; write=0.002 s, sync=0.001 s, total=0.002 s; sync files=0, longest=0.000 s, 
average=0.000 s; distance=18 kB, estimate=458931 kB; lsn=16/54589E08, redo lsn=16/54586F88
2025-04-13 05:31:58.931 UTC [1034758] LOG:  checkpoint starting: immediate force wait


I reproduced this error on three different machines (all are running
Ubuntu 24.04, two with kernel version 6.8, one with 6.11), with PGDATA
located on tmpfs.

Best regards,
Alexander Lakhin
Neon (https://neon.tech)