From: Amit Kapila <amit.kapila@huawei.com>
To: 'Peter Geoghegan' <peter@2ndquadrant.com>
Cc: 'PG Hackers' <pgsql-hackers@postgresql.org>
Subject: Re: Help me develop new commit_delay advice
Date: Thu, 2 Aug 2012 16:45:15 +0530
Message-ID: <002401cd70a0$1837a2b0$48a6e810$@kapila@huawei.com> (raw)
In-Reply-To: <CAEYLb_WmUjTLctsJKTCCO+VVKpKa=tWywEhkRP9D6k=hOPSs+w@mail.gmail.com>
References: <CAEYLb_WtD+Ew3k6RZuL6ydsowoYbMKJWa6w+cNH-kzngAzN16g@mail.gmail.com>
<-5853706607335123168@unknownmsgid>
<CAEYLb_WmUjTLctsJKTCCO+VVKpKa=tWywEhkRP9D6k=hOPSs+w@mail.gmail.com>
> From: Peter Geoghegan [mailto:peter@2ndquadrant.com]
> Sent: Wednesday, August 01, 2012 8:49 PM
On 1 August 2012 15:14, Amit Kapila <amit.kapila@huawei.com> wrote:
>> I shall look into this aspect also(setting commit_delay based on raw
sync).
>> You also suggest if you want to run the test with different
configuration.
> Well, I was specifically interested in testing if half of raw sync
> time was a widely useful setting, across a variety of different,
> though representative I/O subsystems. Unfortunately, without some
> context about raw sync speed to go along with your numbers, I cannot
> advance or disprove that idea.
Raw sync speed data
--------------------------
2 seconds per test
O_DIRECT supported on this platform for open_datasync and open_sync.
Compare file sync methods using one 8kB write:
(in wal_sync_method preference order, except fdatasync
is Linux's default)
open_datasync n/a
fdatasync 165.506 ops/sec
fsync 166.647 ops/sec
fsync_writethrough n/a
open_sync 164.654 ops/sec
165.506 * 8KB operations can perform in one sec.
so 1 * 8KB operation takes 6.042 msec.
> It would also have been nice to see a baseline number of 0 too, to get
> an idea of how effective commit_delay may now be. However, that's
> secondary.
In the data sent yesterday commit_delay=0 was there.
With Regards,
Amit Kapila.
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To: pgsql-performance@postgresql.org
Cc: amit.kapila@huawei.com, peter@2ndquadrant.com, pgsql-hackers@postgresql.org
Subject: Re: Help me develop new commit_delay advice
In-Reply-To: <002401cd70a0$1837a2b0$48a6e810$@kapila@huawei.com>
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