| From: | Robert Haas <robertmhaas(at)gmail(dot)com> |
|---|---|
| To: | James Bottomley <James(dot)Bottomley(at)hansenpartnership(dot)com> |
| Cc: | Andres Freund <andres(at)2ndquadrant(dot)com>, Josh Berkus <josh(at)agliodbs(dot)com>, Hannu Krosing <hannu(at)2ndquadrant(dot)com>, Trond Myklebust <trondmy(at)gmail(dot)com>, Kevin Grittner <kgrittn(at)ymail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org>, Dave Chinner <david(at)fromorbit(dot)com>, Joshua Drake <jd(at)commandprompt(dot)com>, Claudio Freire <klaussfreire(at)gmail(dot)com>, Mel Gorman <mgorman(at)suse(dot)de>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, "lsf-pc(at)lists(dot)linux-foundation(dot)org" <lsf-pc(at)lists(dot)linux-foundation(dot)org>, Magnus Hagander <magnus(at)hagander(dot)net> |
| Subject: | Re: [Lsf-pc] Linux kernel impact on PostgreSQL performance |
| Date: | 2014-01-14 17:14:07 |
| Message-ID: | CA+TgmoYng=xyC7a5cDSuX0u9r30akrDmFNnOjwam2z+NHYUDwA@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tue, Jan 14, 2014 at 12:12 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
> In terms of avoiding double-buffering, here's my thought after reading
> what's been written so far. Suppose we read a page into our buffer
> pool. Until the page is clean, it would be ideal for the mapping to
Correction: "For so long as the page is clean..."
> be shared between the buffer cache and our pool, sort of like
> copy-on-write. That way, if we decide to evict the page, it will
> still be in the OS cache if we end up needing it again (remember, the
> OS cache is typically much larger than our buffer pool). But if the
> page is dirtied, then instead of copying it, just have the buffer pool
> forget about it, because at that point we know we're going to write
> the page back out anyway before evicting it.
>
> This would be pretty similar to copy-on-write, except without the
> copying. It would just be forget-from-the-buffer-pool-on-write.
--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company
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