Horton

Re: shared-memory based stats collector

Kyotaro Horiguchi <horikyota.ntt@gmail.com>

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From: Kyotaro Horiguchi <horikyota.ntt@gmail.com>
To: thomas.munro@gmail.com
Cc: tomas.vondra@2ndquadrant.com, andres@anarazel.de, a.zakirov@postgrespro.ru, alvherre@2ndquadrant.com, ah@cybertec.at, magnus@hagander.net, robertmhaas@gmail.com, tgl@sss.pgh.pa.us, pgsql-hackers@postgresql.org
Date: 2019-07-10T04:35:52Z
Lists: pgsql-hackers 
At Thu, 04 Jul 2019 19:27:54 +0900 (Tokyo Standard Time), Kyotaro Horiguchi <horikyota.ntt@gmail.com> wrote in <20190704.192754.27063464.horikyota.ntt@gmail.com>
>     #db  #tbl  #clients  #iter  #xactlen #referers
> A1:   1     1         1  20000        10        0
> A2:   1     1         1  20000        10        1
> B1:   1     1        90   2000        10        0
> B2:   1     1        90   2000        10        1
> C1:   1    50        90   2000        10        0
> C2:   1    50        90   2000        10        1
> D1:  50     1        90   2000        10        0
> D2:  50     1        90   2000        10        1
> E1:  50     1        90   2000        10       10
> F1:  50     1        10   2000        10       90
> 
> 
> 
>                 master                               patched
>         updator       referrer               updator       referrer       
>        time / stdev  count / stdev          time / stdev   count / stdev    
> A1: 1769.13 / 71.87                      1729.97 / 61.58
> A2: 1903.94 / 75.65  2906.67 /  78.28    1849.41 / 43.00  2855.33 /  62.95
> B1: 2967.84 /  9.88                      2984.20 /  6.10
> B2: 3005.38 /  5.32   253.00 /  33.09    3007.26 /  5.70   253.33 /  60.63
> C1: 3066.14 / 13.80                      3069.34 / 11.65
> C2: 3353.66 /  8.14   282.92 /  20.65    3341.36 / 12.44   251.65 /  21.13
> D1: 2977.12 /  5.12                      2991.60 /  6.68
> D2: 3005.80 /  6.44   252.50 /  38.34    3010.58 /  7.34   282.33 /  57.07
> E1: 3255.47 /  8.91   244.02 /  17.03    3293.88 / 18.05   249.13 /  14.58
> F1: 2620.85 /  9.17   202.46 /   3.35    2668.60 / 41.04   208.19 /   6.79
> 
> 
> ratio (100: same, smaller value means patched version is faster)
> 
>           updator          referrer
>      patched/master(%)    master/patched (%)
> A1:          97.79            -
> A2:          97.14          101.80
> B1:         100.55
> B2:         100.06           99.87
> C1:         100.10
> C2:          99.63          112.43
> D1:         100.49
> D2:         100.16           89.43
> E1:         101.18           97.95
> F1:         101.82           97.25
> 
> 
> Mmm... I don't see distinctive tendency.. Referrer side shows
> larger fluctuation but I'm not sure that suggests something
> meaningful.
> 
> I'll rerun the bencmarks with loger period (many itererations).

I put more puressure to the system.

G1: 1 db, 400 clients, 1000 tables, 20000 loops/client, 1000 query/tr, 0 reader
G2: 1 db, 400 clients, 1000 tables, 20000 loops/client, 1000 query/tr, 1 reader


Result:
                master                               patched
           updator        referrer               updator       referrer       
         time / stdev   count / stdev          time / stdev   count / stdev    
G1: 125946.22 / 796.83                    125227.24 / 89.82
G2: 126463.47 / 81.87 1985.70 /  33.96    125427.95 / 82.35 1985.60 /  55.24

Ratio: (100: same, smaller value means patched version is faster)

          updator          referrer
     patched/master(%)    master/patched (%)
G1:          99.40            -
G2:          99.18          100.0

Slightly faster, or maybe significantly enough considering the
stdev. More crucial difference is shown outside the
numbers. Non-patched version complained that (incorrectly) "stats
collector not respond, used stale stats" many times, which is not
seen on patched version. That means that the reader reads older
numbers as far as 1 second ago. (It might be good that writer
should complain about update holdoff for more than, say 0.75s.)


CF-bot warned that it doesn't work on Windows. I'm experiencing
an very painful time to wait for tortoise git is walking slowly
as its name suggests. It would be fixed in the next version.

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.