Re: Terrible VM in 2.4.11+?

From: Jens Axboe (axboe@suse.de)
Date: Wed Jul 10 2002 - 03:49:04 EST


On Wed, Jul 10 2002, Thomas Tonino wrote:
> J.A. Magallon wrote:
>
> >Seriously, if you have that kind of problems, take the -aa kernel and use
> >it.
> >I use it regularly and it behaves as one would expect, and fast.
> >And please, report your results...
>
> I run a 2 cpu server with 16 disks and around 5 megabytes of writes a
> second. With plain 2.4.18 (using the feral.com qlogic driver) and 2GB
> ram, this seemed okay. Upgrading to 4GB ram slowed the system down, and
> normal shell commands became quite unresponsive with 4GB.
>
> So we built a second server, with 2.4.19-pre9-aa2 using the qlogic
> driver in the kernel. That driver needs patching, as it will otherwise
> get stuck in a 'no handle slots' condition. Used a patch that I posted
> to linux-scsi a while ago.

That's probably not just a mm issue, if you use stock 2.4.18 with 4GB
ram you will spend oodles of time bounce buffering i/o. 2.4.19-pre9-aa2
includes the block-highmem stuff, which enables direct-to-highmem i/o,
if you enabled the CONFIG_HIGHIO option.

In short, not an apples-to-apples comparison :-)

-- 
Jens Axboe

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