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Re: BUG #4575: All page cache in shared_buffers pinned (duplicated by OS, always)

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Scott Carey <scott(at)richrelevance(dot)com>
Cc: "pgsql-bugs(at)postgresql(dot)org" <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: BUG #4575: All page cache in shared_buffers pinned (duplicated by OS, always)
Date: 2008-12-11 21:16:24
Message-ID: 11220.1229030184@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-bugs
Scott Carey <scott(at)richrelevance(dot)com> writes:
> I am 99.9% certian its not a fluke of "top" (or 'free').  Or a fluke with the drop_caches linux vm signal.  Otherwise, the system would not spin at 100% System cpu getting no work done if an attempt to allocate memory above that threshold, the original symptom that led me down this path of investigation.

That's certainly a kernel bug.

> If there are any ideas on how I could truly distinguish where this bug actually is, or further characterize it in ways that would be useful to that end, that would be great.

It's in the kernel.  Userland doesn't have any way to "pin" OS disk cache
pages in memory, which AFAICT is what you are claiming happens.

			regards, tom lane

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Next:From: Scott CareyDate: 2008-12-11 21:52:20
Subject: Re: BUG #4575: All page cache in shared_buffers pinned (duplicated by OS, always)
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Subject: BUG #4576: Postgres Windows service crashes

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