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Date: Sun, 13 Jan 2002 19:55:14 -0500 (EST)
From: Bill Davidsen <davidsen@tmr.com>
To: Andrea Arcangeli <andrea@suse.de>
cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: Re: [2.4.17/18pre] VM and swap - it's really unusable
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On Tue, 8 Jan 2002, Andrea Arcangeli wrote:

> Note that some of them are bugfixes, without them an luser can hang the
> machine for several seconds on any box with some giga of ram by simple
> reading and writing into a large enough buffer. I think we never had
> time to care merging those bits into mainline yet and this is probably
> the main reason they're not integrated but it's something that should be
> in mainline IMHO.

Or just doing a large write while doing lots of reads... my personal
nemesis is "mkisofs" for backups, which reads lots of small files and
builds a CD image, which suddenly gets discovered by the kernel and
written, seemingly in a monolythic chunk. I MAY be able to improve this
with tuning the bdflush parameters, and I tried some tentative patches
which didn't make a huge gain.

I don't know if the solution lies in forcing write to start when a certain
size of buffers are queued regardless of percentages, or in better
scheduling of reads ahead of writes, or whatever.

-- 
bill davidsen <davidsen@tmr.com>
  CTO, TMR Associates, Inc
Doing interesting things with little computers since 1979.

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