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Re: Async Commit, v21 (now: v22)

From: Heikki Linnakangas <heikki(at)enterprisedb(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Gregory Stark <stark(at)enterprisedb(dot)com>, Simon Riggs <simon(at)2ndquadrant(dot)com>, Peter Eisentraut <peter_e(at)gmx(dot)net>, pgsql-patches(at)postgresql(dot)org, Bruce Momjian <bruce(at)momjian(dot)us>
Subject: Re: Async Commit, v21 (now: v22)
Date: 2007-07-24 14:21:25
Message-ID: 46A60AE5.8080808@enterprisedb.com (view raw or flat)
Thread:
Lists: pgsql-patches
Tom Lane wrote:
> Gregory Stark <stark(at)enterprisedb(dot)com> writes:
>> Without async commits? Do we really want the walwriter doing the
>> majority of the wal-flushing work for normal commits? It seems like
>> that's not going to be any advantage over just having some random
>> backend do the commit.
> 
> Sure: the advantage is that the backends (ie, user query processing)
> don't get blocked on fsync's.  This is not really different from the
> rationale for having the bgwriter.  It's probably most useful for large
> transactions, which up to now generally had to stop and flush the WAL
> buffers every few pages worth of WAL output.

I wonder what it would take to offload the CRC calculation to the wal
writer. And if that would then become a bottleneck, making it actually
counterproductive.

No, not in this release :).

-- 
  Heikki Linnakangas
  EnterpriseDB   http://www.enterprisedb.com

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