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Re: POC: Cache data in GetSnapshotData() - Mailing list pgsql-hackers

From Mithun Cy
Subject Re: POC: Cache data in GetSnapshotData()
Date
Msg-id CAD__OuiwEi5sHe2wwQCK36Ac9QMhvJuqG3CfPN+OFCMb7rdruQ@mail.gmail.com
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In response to Re: POC: Cache data in GetSnapshotData()  (Amit Kapila <amit.kapila16@gmail.com>)
Responses Re: POC: Cache data in GetSnapshotData()
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On Tue, Mar 1, 2016 at 12:59 PM, Amit Kapila <amit.kapila16@gmail.com> wrote:
>Don't we need to add this only when the xid of current transaction is valid?  Also, I think it will be better if we can explain why we need to add the our >own transaction id while caching the snapshot.
I have fixed the same thing and patch is attached.

Some more tests done after that

pgbench write tests: on 8 socket, 64 core machine.

/postgres -c shared_buffers=16GB -N 200 -c min_wal_size=15GB -c max_wal_size=20GB -c checkpoint_timeout=900 -c maintenance_work_mem=1GB -c checkpoint_completion_target=0.9

./pgbench -c $clients -j $clients -T 1800 -M prepared postgres

Inline image 3

A small improvement in performance at 64 thread.

LWLock_Stats data:

ProcArrayLock: Base.

=================

postgresql-2016-03-01_115252.log:PID 110019 lwlock main 4: shacq 1867601 exacq 35625 blk 134682 spindelay 128 dequeue self 28871

postgresql-2016-03-01_115253.log:PID 110115 lwlock main 4: shacq 2201613 exacq 43489 blk 155499 spindelay 127 dequeue self 32751

postgresql-2016-03-01_115253.log:PID 110122 lwlock main 4: shacq 2231327 exacq 44824 blk 159440 spindelay 128 dequeue self 33336

postgresql-2016-03-01_115254.log:PID 110126 lwlock main 4: shacq 2247983 exacq 44632 blk 158669 spindelay 131 dequeue self 33365

postgresql-2016-03-01_115254.log:PID 110059 lwlock main 4: shacq 2036809 exacq 38607 blk 143538 spindelay 117 dequeue self 31008


ProcArrayLock: With Patch.

=====================

postgresql-2016-03-01_124747.log:PID 1789 lwlock main 4: shacq 2273958 exacq 61605 blk 79581 spindelay 307 dequeue self 66088

postgresql-2016-03-01_124748.log:PID 1880 lwlock main 4: shacq 2456388 exacq 65996 blk 82300 spindelay 470 dequeue self 68770

postgresql-2016-03-01_124748.log:PID 1765 lwlock main 4: shacq 2244083 exacq 60835 blk 79042 spindelay 336 dequeue self 65212

postgresql-2016-03-01_124749.log:PID 1882 lwlock main 4: shacq 2489271 exacq 67043 blk 85650 spindelay 463 dequeue self 68401

postgresql-2016-03-01_124749.log:PID 1753 lwlock main 4: shacq 2232791 exacq 60647 blk 78659 spindelay 364 dequeue self 65180

postgresql-2016-03-01_124750.log:PID 1849 lwlock main 4: shacq 2374922 exacq 64075 blk 81860 spindelay 339 dequeue self 67584

-------------Block time of ProcArrayLock has reduced significantly.


ClogControlLock : Base.

===================

postgresql-2016-03-01_115302.log:PID 110040 lwlock main 11: shacq 586129 exacq 268808 blk 90570 spindelay 261 dequeue self 59619

postgresql-2016-03-01_115303.log:PID 110047 lwlock main 11: shacq 593492 exacq 271019 blk 89547 spindelay 268 dequeue self 59999

postgresql-2016-03-01_115303.log:PID 110078 lwlock main 11: shacq 620830 exacq 285244 blk 92939 spindelay 262 dequeue self 61912

postgresql-2016-03-01_115304.log:PID 110083 lwlock main 11: shacq 633101 exacq 289983 blk 93485 spindelay 262 dequeue self 62394

postgresql-2016-03-01_115305.log:PID 110105 lwlock main 11: shacq 646584 exacq 297598 blk 93331 spindelay 312 dequeue self 63279


ClogControlLock : With Patch.

=======================

postgresql-2016-03-01_124730.log:PID 1865 lwlock main 11: shacq 722881 exacq 330273 blk 106163 spindelay 468 dequeue self 80316

postgresql-2016-03-01_124731.log:PID 1857 lwlock main 11: shacq 713720 exacq 327158 blk 106719 spindelay 439 dequeue self 79996

postgresql-2016-03-01_124732.log:PID 1826 lwlock main 11: shacq 696762 exacq 317239 blk 104523 spindelay 448 dequeue self 79374

postgresql-2016-03-01_124732.log:PID 1862 lwlock main 11: shacq 721272 exacq 330350 blk 105965 spindelay 492 dequeue self 81036

postgresql-2016-03-01_124733.log:PID 1879 lwlock main 11: shacq 737398 exacq 335357 blk 105424 spindelay 520 dequeue self 80977

-------------Block time of ClogControlLock has increased slightly.


Will continue with further tests on lower clients.


--
Thanks and Regards
Mithun C Y

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