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Date: Sun, 3 Nov 2002 16:00:41 +0100
From: Jens Axboe <axboe@suse.de>
To: Brian Gerst <bgerst@quark.didntduck.org>
Cc: vasya vasyaev <vasya197@yahoo.com>, linux-kernel@vger.kernel.org
Subject: Re: Machine's high load when HIGHMEM is enabled
Message-ID: <20021103150041.GM807@suse.de>
References: <20021103141753.50480.qmail@web20503.mail.yahoo.com> <3DC5337C.4090506@quark.didntduck.org>
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On Sun, Nov 03 2002, Brian Gerst wrote:
> vasya vasyaev wrote:
> >Hello,
> >
> >I have some strange kind of problem:
> >When HIGHMEM-enabled kernel is used, there is too high
> >CPU load on any task - computer get loaded high while
> >it is doing some minor, usual jobs (load average grows
> >significantly).
> 
> 2.4 can only do I/O to and from lowmem.  This means highmem pages have 

2.4.19 and below, 2.4.20-pre/rc can dma to/from highmem pages just fine.

> to use bounce buffers in lowmem, and th edata is copied to/from highmem 
> which is causing the cpu load.  This has been corrected in 2.5, which 
> can do I/O to any page the device can DMA from.

I seriously doubt this is his problem, sounds like something else. For
gzip to be disk bound (and thus bounce bound) you would need a seriously
fast cpu. And the ssh problem cannot be explained by bouncing either.

-- 
Jens Axboe

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