Re: POC: Cache data in GetSnapshotData()

On Tue, Mar 1, 2016 at 12:59 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)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

[image: 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
EnterpriseDB: http://www.enterprisedb.com