Re: Defaulting wal_sync_method to fdatasync on Linux for 9.1?

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Andres Freund <andres(at)anarazel(dot)de>
Cc: pgsql-performance(at)postgresql(dot)org, Josh Berkus <josh(at)agliodbs(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>
Subject: Re: Defaulting wal_sync_method to fdatasync on Linux for 9.1?
Date: 2010-11-17 01:04:28
Message-ID: 11113.1289955868@sss.pgh.pa.us
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Andres Freund <andres(at)anarazel(dot)de> writes:
> On Wednesday 17 November 2010 01:51:28 Tom Lane wrote:
>> Well, there's a forced fsync after writing the last page of an xlog
>> file, but I don't believe that proves that more than 16MB of xlog
>> buffers is useless. Other processes could still be busy filling the
>> buffers.

> Maybe I am missing something, but I think the relevant AdvanceXLInsertBuffer()
> is currently called with WALInsertLock held?

The fsync is associated with the write, which is not done with insert
lock held. We're not quite that dumb.

regards, tom lane

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