From: | "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com> |
---|---|
To: | Andres Freund <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com> |
Cc: | "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: large regression for parallel COPY |
Date: | 2016-03-30 20:18:44 |
Message-ID: | 56FC34A4.4060008@commandprompt.com |
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Lists: | pgsql-hackers |
On 03/30/2016 01:10 PM, Andres Freund wrote:
> On 2016-03-30 15:50:21 -0400, Robert Haas wrote:
>> On Thu, Mar 10, 2016 at 8:29 PM, Andres Freund <andres(at)anarazel(dot)de> wrote:
>>> Allow to trigger kernel writeback after a configurable number of writes.
>>
>> While testing out Dilip Kumar's relation extension patch today, I
>> discovered (with some help from Andres) that this causes nasty
>> regressions when doing parallel COPY on hydra (3.2.6-3.fc16.ppc64,
>> lousy disk subsystem).
Unless Fedora/Redhat fixed the 3.2 kernel in a subsequent patch (.6-3?)
then I would look hard right at that. The kernel from 3.2 - 3.8 is going
to be miserable for anything that is doing concurrent writes. I
understand that this is a regression regardless but I think we need
wider testing to see if the changes are somehow related.
Sincerely,
jD
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