From: David Boreham <david_list@boreham.org>
To: pgsql-hackers@postgresql.org
Subject: Re: ice-broker scan thread
Date: Wed, 30 Nov 2005 07:33:18 -0700
Message-ID: <438DB82E.7060507@boreham.org> (raw)
In-Reply-To: <Pine.LNX.4.58.0511300826120.23317@linuxworld.com.au>
References: <Pine.LNX.4.58.0511282217470.13586@josh.db>
<Pine.LNX.4.58.0511291429330.18112@linuxworld.com.au>
<20051129110214.GA31333@svana.org>
<438C76DA.4060801@boreham.org>
<20051129164651.GF31333@svana.org>
<438C8FD9.3090302@boreham.org>
<Pine.LNX.4.58.0511300826120.23317@linuxworld.com.au>
>Yes. The O_DIRECT issue is my biggest concern about Linux at the moment.
>That being said, the plan is to only pre-fetch the next N blocks, where N
>< 32, and to read them into the local buffer cache. In a situation where
>space in the cache low (and prefetched pages might be pushed out before we
>even get to read them), we need to provide such information to the
>readahead mechanism so that it can reduce the number of blocks which it
>prefetches.
>
>
>
>
Would you open a separate handle O_DIRECT, just for the prefetch ?
My experience with O_DIRECT and databases in the past has not been
great : what you gain with being able to control your own caching you loose
(and more) in other ways.
BTW, has anyone tried O_DIRECT and the prefetch idea on Linux ?
I'm wondering if it may not work (because the read data won't get cached
in the fs cache due to O_DIRECT).
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To: pgsql-hackers@postgresql.org
Cc: david_list@boreham.org
Subject: Re: ice-broker scan thread
In-Reply-To: <438DB82E.7060507@boreham.org>
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