Re: large regression for parallel COPY

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@anarazel.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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