Re: READAHEAD

[age]

Andrew Morton wrote:
> Andrew Morton <akpm@xxxxxxxx> wrote:
>
> > Please, just use time, cat, dd, etc.
> >
> > 	mount /dev/xxx /mnt/yyy
> > 	dd if=/dev/zero of=/mnt/yyy/x bs=1M count=1024
> > 	umount /dev/xxx
> > 	mount /dev/xxx /mnt/yyy
> > 	time cat /mnt/yyy/x > /dev/null
>
>
> And you can do the same against /dev/hdaN if you have a scratch
> partition; that would be interesting.


Hi Andrew,

Here are the new test results.


hdparm -a0
Timing buffered disk reads:   52 MB in  3.07 seconds =  16.94 MB/sec

wuuk:~# dd if=/dev/zero of=/home/test/test bs=1M count=34000
34000+0 records in
34000+0 records out
35651584000 bytes transferred in 922.018299 seconds (38666894 bytes/sec)

wuuk:~# time cat /home/test/test > /dev/null

real    33m21.785s
user    0m19.263s
sys     16m31.853s
wuuk:~# time rm /home/test/test

real    1m35.676s
user    0m0.001s
sys     0m6.679s

hdparm -a16
Timing buffered disk reads:  120 MB in  3.05 seconds =  39.39 MB/sec

wuuk:~# dd if=/dev/zero of=/home/test/test bs=1M count=34000
34000+0 records in
34000+0 records out
35651584000 bytes transferred in 920.669609 seconds (38723537 bytes/sec)

wuuk:~# time cat /home/test/test > /dev/null

real    22m4.180s
user    0m18.464s
sys     10m42.722s
wuuk:~# time rm /home/test/test

real    1m35.642s
user    0m0.003s
sys     0m6.635s

hdparm -a256
Timing buffered disk reads:  134 MB in  3.00 seconds =  44.61 MB/sec

wuuk:~# dd if=/dev/zero of=/home/test/test bs=1M count=34000
34000+0 records in
34000+0 records out
35651584000 bytes transferred in 920.412114 seconds (38734371 bytes/sec)

wuuk:~# time cat /home/test/test > /dev/null

real    13m24.228s
user    0m10.306s
sys     3m3.256s
wuuk:~# time rm /home/test/test

real    1m35.900s
user    0m0.002s
sys     0m6.695s

hdparm -a4096
Timing buffered disk reads:  168 MB in  3.01 seconds =  55.82 MB/sec

wuuk:~# dd if=/dev/zero of=/home/test/test bs=1M count=34000
34000+0 records in
34000+0 records out
35651584000 bytes transferred in 920.198902 seconds (38743346 bytes/sec)

wuuk:~# time cat /home/test/test > /dev/null

real    15m25.848s
user    0m10.716s
sys     3m5.103s
wuuk:~# time rm /home/test/test

real    1m36.205s
user    0m0.003s
sys     0m6.743s

I think you were right  :-)

groetjes,

Age Huisman













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