| From: | Mike Ivanov <mikei(at)activestate(dot)com> |
|---|---|
| To: | Scott Carey <scott(at)richrelevance(dot)com> |
| Cc: | Scott Marlowe <scott(dot)marlowe(at)gmail(dot)com>, Sean Ma <seanxma(at)gmail(dot)com>, "pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: random slow query |
| Date: | 2009-07-01 00:58:46 |
| Message-ID: | 4A4AB4C6.8070808@activestate.com |
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| Thread: | |
| Lists: | pgsql-performance |
Scott Carey wrote:
> the OS can either quickly allocate to the process or
> the page cache from the free buffers, or more slowly take from the page
> cache, or even more slowly page out a process page.
>
Aha, now it all makes sense.
> I like to use the '5 second rule'. dirty_background_ratio should be sized
> so that it takes about 5 seconds to flush to disk in optimal conditions.
> dirty_ratio should be 2x to 5x this depending on your application's needs --
> for a system with well tuned postgres checkpoints, smaller tends to be
> better to limit stalls while waiting for the checkpoint fsync to finish.
>
Thanks a lot, this is invaluable information.
Regards,
Mike
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