| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Andres Freund <andres(at)2ndquadrant(dot)com> |
| Cc: | pgsql-performance(at)postgresql(dot)org, Maxim Boguk <maxim(dot)boguk(at)gmail(dot)com>, David Kerr <dmk(at)mr-paradox(dot)net> |
| Subject: | Re: Massive I/O spikes during checkpoint |
| Date: | 2012-07-10 13:36:35 |
| Message-ID: | CAMkU=1zq2DDFnnoqK_TnFgzz7WF5SSTjvAVU7ga2Ljbpu_yECQ@mail.gmail.com |
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| Lists: | pgsql-performance |
On Tue, Jul 10, 2012 at 5:44 AM, Andres Freund <andres(at)2ndquadrant(dot)com> wrote:
> On Tuesday, July 10, 2012 08:14:00 AM Maxim Boguk wrote:
>>
>> So kernel doesn't start write any pages out in background before it has at
>> least 13Gb dirty pages in kernel memory.
>> And at end of the checkpoint kernel trying flush all dirty pages to disk.
> Thast not entirely true. The kernel will also writeout pages which haven't
> been written to for dirty_expire_centisecs.
There seems to be many situations in which it totally fails to do that.
Although I've never been able to categorize just what those situations are.
Cheers,
Jeff
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