Performance question

From: Achim Leubner (achim@vortex.de)
Date: Mon Jan 17 2000 - 07:15:04 EST


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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