Messages in this thread | | | Date | Thu, 8 Jun 2006 09:43:56 +0200 | From | Voluspa <> | Subject | Re: [PATCH] readahead: initial method - expected read size - fix fastcall |
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On Tue, 6 Jun 2006 10:57:28 +0800 Fengguang Wu wrote: [...] > Would you test two simple commands by the way? > > time (find / >/dev/null) > (repeat and drop the first result) > > dd if=/dev/zero of=sparse bs=1M seek=5000 count=1 > > time cp sparse /dev/null > (repeat and drop the first result) > > These commands measure the pure cpu(or software) overhead of the > readahead logics, without ever hitting the physical device. I have > no 64bit cpu numbers for them yet ;)
The commands don't make sense (I'm in bash)... Also, I refuse to overwrite /dev/null ;-) I've done a test with "cat" but the first and second run of it are the same, so it does touch the disk, it seems:
root:sleipner:~# grep setra /etc/rc.d/rc.local #/sbin/blockdev --setra 2048 /dev/hda /sbin/blockdev --setra 256 /dev/hda root:sleipner:~# uname -r 2.6.17-rc5-git10-ar2
root:sleipner:~# time find / >/dev/null
real 3m34.119s user 0m1.118s sys 0m5.844s root:sleipner:~# time find / >/dev/null
real 0m2.949s user 0m0.691s sys 0m2.253s root:sleipner:~# dd if=/dev/zero of=sparse bs=1M seek=5000 count=1 1+0 records in 1+0 records out root:sleipner:~# time cat sparse >/dev/null
real 0m9.377s user 0m0.140s sys 0m8.715s root:sleipner:~# time cat sparse >/dev/null
real 0m9.593s user 0m0.138s sys 0m8.680s *******************************************************************
root:sleipner:~# grep setra /etc/rc.d/rc.local /sbin/blockdev --setra 2048 /dev/hda #/sbin/blockdev --setra 256 /dev/hda root:sleipner:~# uname -r 2.6.17-rc5-git10-ar2
root:sleipner:~# time find / >/dev/null
real 3m33.037s user 0m1.112s sys 0m5.821s root:sleipner:~# time find / >/dev/null
real 0m2.538s user 0m0.622s sys 0m1.911s root:sleipner:~# dd if=/dev/zero of=sparse bs=1M seek=5000 count=1 1+0 records in 1+0 records out root:sleipner:~# time cat sparse >/dev/null
real 0m11.279s user 0m0.163s sys 0m10.340s root:sleipner:~# time cat sparse >/dev/null
real 0m11.268s user 0m0.154s sys 0m10.412s
Mvh Mats Johannesson -- - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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