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

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Rafał Bilski wrote:
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
Interesting! I haven't tried libata myself on that system, I only have
remote access to it so I'm a bit afraid...
Rafal, I hope that system you run hdparm on isn't the archlinux one! Is
it easy to load an old kernel (even two years old) and do the same test?
If it is, please let me know of the results.

Thanks in advance,
Dimitris


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