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Re: lock contention on parallel COPY ?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>
Cc: Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: lock contention on parallel COPY ?
Date: 2008-09-26 16:38:14
Message-ID: 19475.1222447094@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc> writes:
> heh no log archiving - I actually said that I'm now playing with 
> --truncate-before-load which seems to cause a noticeable performance (as 
> in IO generated) increase but I still see >130000 context switches/s and 
> a profile that looks like:

> samples  %        symbol name
> 55526    16.5614  LWLockAcquire
> 29721     8.8647  DoCopy
> 26581     7.9281  CopyReadLine
> 25105     7.4879  LWLockRelease
> 15743     4.6956  PinBuffer
> 14725     4.3919  heap_formtuple

Still a lot of contention for something, then.  You might try turning on
LWLOCK_STATS (this only requires recompiling storage/lmgr/lwlock.c) to
get some evidence about what.

			regards, tom lane

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