linux-kernel - Re: high system cpu load during intense disk i/o

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Date:	Tue, 07 Aug 2007 00:12:46 +0200
From:	Rafał Bilski <rafalbilski@...eria.pl>
To:	Dimitrios Apostolou <jimis@....net>
Cc:	linux-kernel@...r.kernel.org
Subject: Re: high system cpu load during intense disk i/o

> Hello Rafal,
Hello, 
> However I find it quite possible to have reached the throughput limit 
> because of software (driver) problems. I have done various testing 
> (mostly "hdparm -tT" with exactly the same PC and disks since about 
> kernel 2.6.8 (maybe even earlier). I remember with certainty that read 
> throughput the early days was about 50MB/s for each of the big disks, 
> and combined with RAID 0 I got ~75MB/s. Those figures have been dropping 
> gradually with each new kernel release and the situation today, with 
> 2.6.22, is that hdparm gives maximum throughput 20MB/s for each disk, 
> and for RAID 0 too!
Just tested (plain curiosity).
via82cxxx average result @533MHz:
/dev/hda:
 Timing cached reads:   232 MB in  2.00 seconds = 115.93 MB/sec
 Timing buffered disk reads:   64 MB in  3.12 seconds =  20.54 MB/sec
pata_via average result @533MHz:
/dev/sda:
 Timing cached reads:   234 MB in  2.01 seconds = 116.27 MB/sec
 Timing buffered disk reads:   82 MB in  3.05 seconds =  26.92 MB/sec

Same 2.6.23-rc1-git11 kernel. 
Yes - constant 6MB/s difference (31%). Cool.
> Dimitris
Regards
Rafał

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