| From: | Jeff Janes <jeff(dot)janes(at)gmail(dot)com> |
|---|---|
| To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
| Cc: | Claudio Freire <klaussfreire(at)gmail(dot)com>, Tatsuo Ishii <ishii(at)postgresql(dot)org>, KONDO Mitsumasa <kondo(dot)mitsumasa(at)lab(dot)ntt(dot)co(dot)jp>, Magnus Hagander <magnus(at)hagander(dot)net>, Josh Berkus <josh(at)agliodbs(dot)com>, Stefan Kaltenbrunner <stefan(at)kaltenbrunner(dot)cc>, "Joshua D(dot) Drake" <jd(at)commandprompt(dot)com>, PostgreSQL-Dev <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Why we are going to have to go DirectIO |
| Date: | 2013-12-11 02:33:46 |
| Message-ID: | CAMkU=1xu-1g6a7Kv3TmNXieA15sP+t0v4UXzFgkL=QsCged7Kg@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Tuesday, December 10, 2013, Tom Lane wrote:
> Jeff Janes <jeff(dot)janes(at)gmail(dot)com <javascript:;>> writes:
> > On Tue, Dec 3, 2013 at 11:39 PM, Claudio Freire <klaussfreire(at)gmail(dot)com<javascript:;>
> >wrote:
> >> Problem is, Postgres relies on a working kernel cache for checkpoints.
> >> Checkpoint logic would have to be heavily reworked to account for an
> >> impaired kernel cache.
>
> > I don't think it would need anything more than a sorted checkpoint.
>
> Nonsense. We don't have access to the physical-disk-layout information
> needed to do reasonable sorting; to say nothing of doing something
> intelligent in a multi-spindle environment, or whenever any other I/O
> is going on concurrently.
>
The proposal I was responding to was simply to increase shared_buffers to
80% of RAM *instead of* implementing directIO.
Cheers,
Jeff
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