Re: LWLock optimization for multicore Power machines

From: Bernd Helmle <mailings(at)oopsware(dot)de>
To: Alexander Korotkov <a(dot)korotkov(at)postgrespro(dot)ru>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: LWLock optimization for multicore Power machines
Date: 2017-02-21 14:54:14
Message-ID: 1487688854.3143.3.camel@oopsware.de
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Am Dienstag, den 14.02.2017, 15:53 +0300 schrieb Alexander Korotkov:
> +1
> And you could try to use pg_wait_sampling
> <https://github.com/postgrespro/pg_wait_sampling> to sampling of wait
> events.

I've tried this with your example from your blog post[1] and got this:

(pgbench scale 1000)

pgbench -Mprepared -S -n -c 100 -j 100 -T 300 -P2 pgbench2

SELECT-only:

SELECT * FROM profile_log ;
             ts             |  event_type   |     event     | count 
----------------------------+---------------+---------------+-------
 2017-02-21 15:21:52.45719  | LWLockNamed   | ProcArrayLock |     8
 2017-02-21 15:22:11.19594  | LWLockTranche | lock_manager  |     1
 2017-02-21 15:22:11.19594  | LWLockNamed   | ProcArrayLock |    24
 2017-02-21 15:22:31.220803 | LWLockNamed   | ProcArrayLock |     1
 2017-02-21 15:23:01.255969 | LWLockNamed   | ProcArrayLock |     1
 2017-02-21 15:23:11.272254 | LWLockNamed   | ProcArrayLock |     2
 2017-02-21 15:23:41.313069 | LWLockNamed   | ProcArrayLock |     1
 2017-02-21 15:24:31.37512  | LWLockNamed   | ProcArrayLock |    19
 2017-02-21 15:24:41.386974 | LWLockNamed   | ProcArrayLock |     1
 2017-02-21 15:26:41.530399 | LWLockNamed   | ProcArrayLock |     1
(10 rows)

writes pgbench runs have far more events logged, see the attached text
file. Maybe this is of interest...

[1] http://akorotkov.github.io/blog/2016/03/25/wait_monitoring_9_6/

Attachment Content-Type Size
wait_sampling_profile_writes.txt text/plain 22.8 KB

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