| From: | Simon Riggs <simon(at)2ndQuadrant(dot)com> |
|---|---|
| To: | Amit Kapila <amit(dot)kapila(at)huawei(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Andres Freund <andres(at)2ndquadrant(dot)com>, Greg Smith <greg(at)2ndquadrant(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Move unused buffers to freelist |
| Date: | 2013-07-03 12:39:53 |
| Message-ID: | CA+U5nMK+kGz8FM-oDepsYszd6xTiF9ghEJvsE1G41cg_HaA6DQ@mail.gmail.com |
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| Lists: | pgsql-hackers |
On 3 July 2013 12:56, Amit Kapila <amit(dot)kapila(at)huawei(dot)com> wrote:
> >My perspectives here would be
>
> > * BufFreelistLock is a huge issue. Finding a next victim block needs to
> be
> an O(1) operation, yet it is currently much worse than that. Measuring
> > contention on that lock hides that problem, since having shared buffers
> lock up for 100ms or more but only occasionally is a huge problem, even if
> it
> > doesn't occur frequently enough for the averaged contention to show as an
> issue.
>
> To optimize finding next victim buffer, I am planning to run the clock
> sweep in background. Apart from that do you have any idea to make it closer
> to O(1)?
>
Yes, I already posted patches to attentuate the search time. Please check
back last few CFs of 9.3
--
Simon Riggs http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services
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