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

Rafał Bilski
2007-08-06T22:13:13Z

> 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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