[6167] in linux-scsi channel archive
Re: how to get maximum datarate from SCSI
daemon@ATHENA.MIT.EDU (Dietmar Stein)
Wed Mar 24 17:52:30 1999
Date: Wed, 24 Mar 1999 22:39:06 +0100
To: Mateu Batle i Sastre <mbatle@iname.com>, linux-scsi@vger.rutgers.edu
From: dstein2203@t-online.de (Dietmar Stein)
Hi
You can mount your disks with sync-option in order to go around the
buffer/cache. Have a try (e.g. mount -o sync /dev/sda1 /mnt) and compare the
performance.
I think you will go back to the async-mode very fast...
Dietmar
Mateu Batle i Sastre wrote:
> Hi everybody,
>
> I'm trying to get the maximum transfer datarate from several SCSI disks
> from a user application. I think the problem now is that all the transfers
> go through the buffer cache, which implies a lot of memory copy and this
> bounds the maximum I/O. It should be possible to access the SCSI disks
> bypassing the buffer cache of the block devices.
> Is there any easy way to do this ?
>
> My first option would be to use some special flag when openning the file
> to avoid going through the buffer cache. But I have not found anything
> similar.
>
> If not, I would have to modify the sd.c to to perform direct transfers
> without using the buffer cache.
>
> Bye,
> Mateu Batle
>
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