[7849] in linux-scsi channel archive
Re: Performance question
daemon@ATHENA.MIT.EDU (D. Lance Robinson)
Mon Jan 17 19:37:58 2000
Message-ID: <388358CE.64983907@airways.com>
Date: Mon, 17 Jan 2000 11:00:46 -0700
From: "D. Lance Robinson" <lancer@airways.com>
Reply-To: lancer@airways.com
MIME-Version: 1.0
To: Achim Leubner <achim@vortex.de>
Cc: linux-scsi@vger.rutgers.edu, linux-kernel@vger.rutgers.edu
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Achim,
I'm not familiar with your driver, but there may be a scatter gather limit
which only allows 64KB at a time.
<>< Lance.
Achim Leubner wrote:
> Hello,
>
> I'm the maintainer of the ICP Disk Array Controller driver (gdth) and
> I have a performance question.
> I read a big file on an ext2 filesystem under Linux 2.2.xx with "dd"
> with a read block size of 1 MB.
> In the gdth scsi driver and therefore on the controller I see
> 1. read commands with a size of <= 64 KB only
> 2. max. 2 simultaneous read commands only
> If the commands are splitted into 64 KB I/O's, why I don't see 16
> simultaneous commands (64 KB * 16 = 1 MB) ?
> Could the reason be the read ahead cache implemented in
> mm/filemap.c ?
> Is there any possibility to change any filesystem/kernel parameters
> to get I/O's with greater size or to get more simultaneous I/O's ?
>
> Any hints are greatly appreciated.
>
> Regards
> Achim
>
>
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