Hi Jeff, On 06/27/2010 09:48 PM, Jeff Moyer wrote: > Tao Ma writes: > >> Hi Jeff, >> >> On 06/23/2010 05:30 PM, Tao Ma wrote: >>> Hi Jeff, >>> >>> On 06/23/2010 05:34 AM, Jeff Moyer wrote: >>>> Hi, >>>> >>>> Running iozone with the fsync flag, or fs_mark, the performance of CFQ is >>>> far worse than that of deadline for enterprise class storage when dealing >>>> with file sizes of 8MB or less. I used the following command line as a >>>> representative test case: >>>> >>>> fs_mark -S 1 -D 10000 -N 100000 -d /mnt/test/fs_mark -s 65536 -t 1 -w >>>> 4096 -F >>>> >>>> When run using the deadline I/O scheduler, an average of the first 5 >>>> numbers >>>> will give you 448.4 files / second. CFQ will yield only 106.7. With >>>> this patch series applied (and the two patches I sent yesterday), CFQ now >>>> achieves 462.5 files / second. >>> which 2 patches? Could you paste the link or the subject? Just want to >>> make my test env like yours. ;) >>> As Joel mentioned in another mail, ocfs2 also use jbd/jbd2, so I'd like >>> to give it a try and give you some feedback about the test. >> I am sorry to say that the patch make jbd2 locked up when I tested >> fs_mark using ocfs2. >> I have attached the log from my netconsole server. After I reverted >> the patch [3/3], the box works again. > > I can't reproduce this, unfortunately. Also, when building with the > .config you sent me, the disassembly doesn't line up with the stack > trace you posted. > > I'm not sure why yielding the queue would cause a deadlock. The only > explanation I can come up with is that I/O is not being issued. I'm > assuming that no other I/O will be completed to the file system in > question. Is that right? Could you send along the output from sysrq-t? yes, I just mounted it and begin the test, so there should be no outstanding I/O. So do you need me to setup another disk for test? I have attached the sysrq output in sysrq.log. please check. btw, I also met with a NULL pointer deference in cfq_yield. I have attached the null.log also. This seems to be related to the previous deadlock and happens when I try to remount the same volume after reboot and ocfs2 try to do some recovery. Regards, Tao