Am 20.08.2013 19:15, schrieb Mihai T. Lazarescu: > On Tue, Aug 20, 2013 at 03:56:56PM +0200, Heinz Diehl wrote: >> All these numbers are pointless, because when I see >> your results I'm quite shure you did run the test without >> generating loads of disk I/O in parallel. What you actually >> measured is the latency in idle state ;-) >> >> Open a console and run >> while : ; do time sh -c "dd if=/dev/zero of=bigfile bs=8M count=256 ; sync; >> rm bigfile"; done >> >> Then, open another one and run fsync-tester. The numbers >> that count to compare different elevators on your system >> is the output fsync-tester generates while your machine is >> generating the "bigfile". > > Thanks Heinz! Indeed, I took every precaution to leave the > machine still. :-) > > Here are the program numbers while running the script: > > CFQ: > write time: 0.0010s fsync time: 0.8647s > write time: 0.1340s fsync time: 3.1220s > write time: 2.1435s fsync time: 2.8134s > write time: 0.1458s fsync time: 8.3726s > write time: 0.0005s fsync time: 1.0401s > write time: 0.0175s fsync time: 1.0270s > write time: 4.0406s fsync time: 0.0321s > write time: 0.0005s fsync time: 4.8683s > write time: 0.0004s fsync time: 0.3178s > > Deadline run1: > write time: 0.0009s fsync time: 82.3477s > > Deadline run2: > write time: 0.0007s fsync time: 659.2289s
all these numbers are also pointless because the moment of the sync-command in the dd-loop makes the most difference and depending when it happens exactly it slows down other things however, i had running the loop and below the first result is "cfq" and the second one "deadline" on a simple Software-RAID10 with 4x2 TB 7200 RPM ROTATING disks looking at all values "deadline" is faster because far away from 12 seconds and in reality there is no difference between both while on IO-workloads like virtualization "deadline" is usually faster __________________________________________________________ [root@srv-rhsoft:/data]$ fsync-tester.sh setting up random write file done setting up random write file starting fsync run starting random io! write time: 0.0005s fsync time: 1.3178s write time: 0.0004s fsync time: 0.1273s write time: 0.0495s fsync time: 5.1039s write time: 0.0719s fsync time: 3.6246s write time: 0.0005s fsync time: 0.3371s write time: 0.0003s fsync time: 12.1480s write time: 0.0006s fsync time: 0.6380s write time: 0.0004s fsync time: 2.1844s write time: 0.0004s fsync time: 2.3435s write time: 0.0006s fsync time: 0.4382s run done 10 fsyncs total, killing random writer setting up random write file done setting up random write file starting fsync run starting random io! write time: 0.0005s fsync time: 0.0607s write time: 0.0003s fsync time: 5.3616s write time: 0.1376s fsync time: 2.7067s write time: 0.0003s fsync time: 0.1988s write time: 0.0003s fsync time: 0.5727s write time: 0.0003s fsync time: 3.0089s write time: 0.0256s fsync time: 1.2177s write time: 0.0212s fsync time: 0.0670s write time: 0.0179s fsync time: 0.2713s write time: 0.0002s fsync time: 1.2871s write time: 0.0162s fsync time: 2.8389s write time: 0.0319s fsync time: 1.8701s run done 12 fsyncs total, killing random writer __________________________________________________________ [root@srv-rhsoft:/data]$ cat /scripts/fsync-tester.sh #!/usr/bin/bash cd /data/ # while : ; do time sh -c "dd if=/dev/zero of=bigfile bs=8M count=256 ; sync; rm bigfile"; done echo cfq > /sys/block/sda/queue/scheduler echo cfq > /sys/block/sdb/queue/scheduler echo cfq > /sys/block/sdc/queue/scheduler echo cfq > /sys/block/sdd/queue/scheduler rm -f /data/fsync-tester*file sync echo "" fsync-tester echo deadline > /sys/block/sda/queue/scheduler echo deadline > /sys/block/sdb/queue/scheduler echo deadline > /sys/block/sdc/queue/scheduler echo deadline > /sys/block/sdd/queue/scheduler rm -f /data/fsync-tester*file sync echo "" fsync-tester __________________________________________________________ /dev/md1 ext4 29G 6,0G 23G 21% / /dev/md0 ext4 477M 30M 443M 7% /boot /dev/md2 ext4 3,6T 1,7T 1,9T 48% /mnt/data Personalities : [raid10] [raid1] md2 : active raid10 sdd3[0] sdc3[5] sda3[4] sdb3[3] 3875222528 blocks super 1.1 512K chunks 2 near-copies [4/4] [UUUU] bitmap: 5/29 pages [20KB], 65536KB chunk md1 : active raid10 sda2[4] sdb2[3] sdc2[5] sdd2[0] 30716928 blocks super 1.1 512K chunks 2 near-copies [4/4] [UUUU] bitmap: 0/1 pages [0KB], 65536KB chunk md0 : active raid1 sdb1[3] sda1[4] sdd1[0] sdc1[5] 511988 blocks super 1.0 [4/4] [UUUU] unused devices: <none>
signature.asc
Description: OpenPGP digital signature
-- users mailing list users@lists.fedoraproject.org To unsubscribe or change subscription options: https://admin.fedoraproject.org/mailman/listinfo/users Fedora Code of Conduct: http://fedoraproject.org/code-of-conduct Guidelines: http://fedoraproject.org/wiki/Mailing_list_guidelines Have a question? Ask away: http://ask.fedoraproject.org