Horton

Re: shared-memory based stats collector

Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>

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From: Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp>
To: andres@anarazel.de
Cc: tomas.vondra@2ndquadrant.com, alvherre@2ndquadrant.com, ah@cybertec.at, magnus@hagander.net, robertmhaas@gmail.com, tgl@sss.pgh.pa.us, pgsql-hackers@postgresql.org
Date: 2019-02-18T12:35:31Z
Lists: pgsql-hackers

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At Fri, 15 Feb 2019 17:29:00 +0900 (Tokyo Standard Time), Kyotaro HORIGUCHI <horiguchi.kyotaro@lab.ntt.co.jp> wrote in <20190215.172900.84235698.horiguchi.kyotaro@lab.ntt.co.jp>
> > I don't think this is all that close to being committable :(
> 
> I'm going to work harder on this. The remaining taks just now are
> the follows:
> 
> - Separte shared database stats from db_stats hash.

Finally I didn't do that. It lead to more complexy.

> - Consider relaxing dbentry locking.

Lock on a dbenty by dshash was useless to protect it from DROP
DB, so I relaxed locking on dbentry so that the dshash lock is
immediately released after fetching it.  On the other hand table
and function counter hash are just destroyed at the time of a
counter reset ant it required some kind of arbitration. I could
introduce dshash_reset() but it requires many lwlocks, which
would be too-much. Instaed, I inroduced two-set of hash_handles
and reference counter in PgStat_StatDBEntry to stash out
to-be-removed-but-currently-accessed hash. pin_hashes() and
unpin_hashes(), and reset_dbentry_counters() are that.

After all, dbentries are no longer isolated by dshash partition
lock on updates, so every dbentry instead has LWLock to do
that. (tabentries/funcentries are still isolated by dshash).

pgstat_apply_tabstats() runs single-pass. Previously ran
two-passes, shared db and my database.

We could eliminate pgStatPendingTabHash, but manipulating TSA

I'm trying removing pgStatPendingTabHash it does't work yet. I'll
include it in the next version.

> - Try removing pgStatPendingFunctions

Done. pgStatPendingDeadLocks and pgStatPendingTempfiles are also
removed.

> - ispell on it.

I fixed many misspellings..

- Fixed several silly mistakes in the previous version.

I'll post the next version soon.

regards.

-- 
Kyotaro Horiguchi
NTT Open Source Software Center

Commits

  1. Improve comment about dropped entries in pgstat.c

  2. Fix temporary memory leak in system table index scans

  3. pgstat: set timestamps of fixed-numbered stats after a crash.

  4. pgstat: Update docs to match the shared memory stats reality.

  5. pgstat: Hide instability in stats.spec with -DCATCACHE_FORCE_RELEASE.

  6. pgstat: add/extend tests for resetting various kinds of stats.

  7. Add minimal tests for recovery conflict handling.

  8. pgstat: test stats interactions with physical replication.

  9. pgstat: add tests for handling of restarts, including crashes.

  10. pgstat: add tests for transaction behaviour, 2PC, function stats.

  11. pgstat: add pg_stat_have_stats() test helper.

  12. pgstat: add pg_stat_force_next_flush(), use it to simplify tests.

  13. pgstat: move pgstat.c to utils/activity.

  14. pgstat: store statistics in shared memory.

  15. pgstat: remove stats_temp_directory.

  16. pgstat: rename STATS_COLLECTOR GUC group to STATS_CUMULATIVE.

  17. pgstat: revise replication slot API in preparation for shared memory stats.

  18. pgstat: scaffolding for transactional stats creation / drop.

  19. pgstat: introduce PgStat_Kind enum.

  20. pgstat: prepare APIs used by pgstatfuncs for shared memory stats.

  21. pgstat: add pgstat_copy_relation_stats().

  22. pgstat: rename some pgstat_send_* functions to pgstat_report_*.

  23. pgstat: stats collector references in comments.

  24. pgstat: move transactional code into pgstat_xact.c.

  25. dsm: allow use in single user mode.

  26. dshash: revise sequential scan support.

  27. pgstat: remove some superflous comments from pgstat.h.

  28. pgstat: reorder pgstat.[ch] contents.

  29. pgstat: split different types of stats into separate files.

  30. pgstat: introduce pgstat_relation_should_count().

  31. pgstat: separate "xact level" handling out of relation specific functions.

  32. pgstat: rename pgstat_initstats() to pgstat_relation_init().

  33. pgstat: split out WAL handling from pgstat_{initialize,report_stat}.

  34. pgstat: run pgindent on pgstat.c/h.

  35. pgstat: split relation, database handling out of pgstat_report_stat().

  36. Move code around in StartupXLOG().

  37. pgstat: Prepare to use mechanism for truncated rels also for droppped rels.

  38. pgstat: Split out relation stats handling from AtEO[Sub]Xact_PgStat() etc.

  39. pgstat: Schedule per-backend pgstat shutdown via before_shmem_exit().

  40. Schedule ShutdownXLOG() in single user mode using before_shmem_exit().

  41. Make parallel worker shutdown complete entirely via before_shmem_exit().

  42. pgstat: Bring up pgstat in BaseInit() to fix uninitialized use of pgstat by AV.

  43. pgstat: split reporting/fetching of bgwriter and checkpointer stats.

  44. Split backend status and progress related functionality out of pgstat.c.

  45. Split wait event related code from pgstat.[ch] into wait_event.[ch].

  46. Make archiver process an auxiliary process.

  47. Force to send remaining WAL stats to the stats collector at walwriter exit.

  48. Add pg_stat_database counters for sessions and session time

  49. Collect statistics about SLRU caches

  50. Don't run atexit callbacks in quickdie signal handlers.

  51. Create a "fast path" for acquiring weak relation locks.