Messages in this thread | | | Date | Mon, 12 Nov 2007 04:58:42 -0800 (PST) | From | Martin Knoblauch <> | Subject | Re: iozone write 50% regression in kernel 2.6.24-rc1 |
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----- Original Message ---- > From: "Zhang, Yanmin" <yanmin_zhang@linux.intel.com> > To: Martin Knoblauch <knobi@knobisoft.de> > Cc: a.p.zijlstra@chello.nl; LKML <linux-kernel@vger.kernel.org> > Sent: Monday, November 12, 2007 1:45:57 AM > Subject: Re: iozone write 50% regression in kernel 2.6.24-rc1 > > On Fri, 2007-11-09 at 04:36 -0800, Martin Knoblauch wrote: > > ----- Original Message ---- > > > From: "Zhang, Yanmin" > > > To: a.p.zijlstra@chello.nl > > > Cc: LKML > > > Sent: Friday, November 9, 2007 10:47:52 AM > > > Subject: iozone write 50% regression in kernel 2.6.24-rc1 > > > > > > Comparing with 2.6.23, iozone sequential write/rewrite (512M) has > > > 50% > > > > > regression > > > in kernel 2.6.24-rc1. 2.6.24-rc2 has the same regression. > > > > > > My machine has 8 processor cores and 8GB memory. > > > > > > By bisect, I located patch > > > > > http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h > = > > > 04fbfdc14e5f48463820d6b9807daa5e9c92c51f. > > > > > > > > > Another behavior: with kernel 2.6.23, if I run iozone for many > > > times > > > > > after rebooting machine, > > > the result looks stable. But with 2.6.24-rc1, the first run of > > > iozone > > > > > got a very small result and > > > following run has 4Xorig_result. > > > > > > What I reported is the regression of 2nd/3rd run, because first run > > > has > > > > > bigger regression. > > > > > > I also tried to change > > > /proc/sys/vm/dirty_ratio,dirty_backgroud_ratio > > > > > and didn't get improvement. > > could you tell us the exact iozone command you are using? > iozone -i 0 -r 4k -s 512m >
OK, I definitely do not see the reported effect. On a HP Proliant with a RAID5 on CCISS I get:
2.6.19.2: 654-738 MB/sec write, 1126-1154 MB/sec rewrite 2.6.24-rc2: 772-820 MB/sec write, 1495-1539 MB/sec rewrite
The first run is always slowest, all subsequent runs are faster and the same speed.
> > > I would like to repeat it on my setup, because I definitely see > the > opposite behaviour in 2.6.24-rc1/rc2. The speed there is much > better > than in 2.6.22 and before (I skipped 2.6.23, because I was waiting > for > the per-bdi changes). I definitely do not see the difference between > 1st > and subsequent runs. But then, I do my tests with 5GB file sizes like: > > > > iozone3_283/src/current/iozone -t 5 -F /scratch/X1 > /scratch/X2 > /scratch/X3 /scratch/X4 /scratch/X5 -s 5000M -r 1024 -c -e -i 0 -i 1 > My machine uses SATA (AHCI) disk. >
4x72GB SCSI disks building a RAID5 on a CCISS controller with battery backed write cache. Systems are 2 CPUs (64-bit) with 8 GB memory. I could test on some IBM boxes (2x dual core, 8 GB) with RAID5 on "aacraid", but I need some time to free up one of the boxes.
Cheers Martin
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