On Thu, Apr 19, 2012 at 11:46:02AM -0400, Josef 'Jeff' Sipek wrote: > On Thu, Apr 19, 2012 at 09:48:21AM +1000, Dave Chinner wrote: > > On Wed, Apr 18, 2012 at 11:11:40AM -0400, Josef 'Jeff' Sipek wrote: > > > Greetings! I have a file server that get a pretty nasty load (about 15 > > > million files created every day). After some time, I noticed that the load > > > average spiked up from the usual 30 to about 180. dmesg revealed: > > > > > > [434042.318401] INFO: task php:2185 blocked for more than 120 seconds. > > > [434042.318403] "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > > [434042.318405] php D 000000010675d6cd 0 2185 27306 0x00000000 > > > [434042.318408] ffff88008d735a48 0000000000000086 ffff88008d735938 ffffffff00000000 > > > [434042.318412] ffff88008d734010 ffff88000e28e340 0000000000012000 ffff88008d735fd8 > > > [434042.318416] ffff88008d735fd8 0000000000012000 ffff8807ef9966c0 ffff88000e28e340 > > > [434042.318419] Call Trace: > > > [434042.318442] [<ffffffffa0087a9b>] ? xfs_trans_brelse+0xee/0xf7 [xfs] > > > [434042.318464] [<ffffffffa00689de>] ? xfs_da_brelse+0x71/0x96 [xfs] > > > [434042.318485] [<ffffffffa006df10>] ? xfs_dir2_leaf_lookup_int+0x211/0x225 [xfs] > > > [434042.318489] [<ffffffff8141481e>] schedule+0x55/0x57 > > > [434042.318512] [<ffffffffa0083de2>] xlog_reserveq_wait+0x115/0x1c0 [xfs] > > > [434042.318515] [<ffffffff810381f1>] ? try_to_wake_up+0x23d/0x23d > > > [434042.318539] [<ffffffffa0083f45>] xlog_grant_log_space+0xb8/0x1be [xfs] > > > [434042.318562] [<ffffffffa0084164>] xfs_log_reserve+0x119/0x133 [xfs] > > > [434042.318585] [<ffffffffa0080cf1>] xfs_trans_reserve+0xca/0x199 [xfs] > > > [434042.318605] [<ffffffffa00500dc>] xfs_create+0x18d/0x467 [xfs] > > > [434042.318623] [<ffffffffa00485be>] xfs_vn_mknod+0xa0/0xf9 [xfs] > > > [434042.318640] [<ffffffffa0048632>] xfs_vn_create+0xb/0xd [xfs] > > > [434042.318644] [<ffffffff810f0c5d>] vfs_create+0x6e/0x9e > > > [434042.318647] [<ffffffff810f1c5e>] do_last+0x302/0x642 > > > [434042.318651] [<ffffffff810f2068>] path_openat+0xca/0x344 > > > [434042.318654] [<ffffffff810f23d1>] do_filp_open+0x38/0x87 > > > [434042.318658] [<ffffffff810fb22e>] ? alloc_fd+0x76/0x11e > > > [434042.318661] [<ffffffff810e40b1>] do_sys_open+0x10b/0x1a4 > > > [434042.318664] [<ffffffff810e4173>] sys_open+0x1b/0x1d > > > > > > It makes sense that'd the load average would spike up if some major lock got > > > held longer than it should have been. > > > > That's possibly just IO load. It's waiting for log space to become > > available, and that will only occur when metadata is written back to > > disk. > > Yeah, it could be... > > > What's the storage subsystem, what IO scheduler, the actually > > workload that is running at the time the spike occurs (e.g did > > someone run a directory traversal that changed every indoe?), and so > > on. > > fs3.ess ~ # MegaCli -CfgDsply -aAll > ============================================================================== > Adapter: 0 > Product Name: LSI MegaRAID SAS 9260-16i > Memory: 512MB > BBU: Present > ... > RAID Level : Primary-6, Secondary-0, RAID Level Qualifier-3 .... > /dev/sda4 /var/data/disk0 xfs rw,noatime,attr2,filestreams,delaylog,nobarrier,inode64,logbufs=8,logbsize=256k,noquota 0 0 Only unusual thing is the filestreams allocator is in use... > fs3.ess ~ # xfs_info /var/data/disk0/ > meta-data=/dev/sda4 isize=256 agcount=32, agsize=268435455 blks > = sectsz=512 attr=2 > data = bsize=4096 blocks=8519632640, imaxpct=5 > = sunit=0 swidth=0 blks > naming =version 2 bsize=4096 ascii-ci=0 > log =internal bsize=4096 blocks=521728, version=2 and it is a large log, so that's a definite candidate for long stalls pushing the tail of the log. The typical push that you'll get stalled on is trying to keep 25% fthe log space free, so there's potentially hundreds of megabytes of random 4/8k metadata writes to be done to free that space in the log... > = sectsz=512 sunit=0 blks, lazy-count=1 > realtime =none extsz=4096 blocks=0, rtextents=0 > > As far as the workload is concerned, there's the typical (for us) load of > create 15 million files in a day (pretty standard diurnal distribution as far > as the load is concerned). Half the files are about 300 bytes, and the other > half averages 20kB in size. On this system, the files are never read back. > Since we had a fs corruption recently (due to a power failure & disk caches > being on), our software managed to dump about 25 million files onto /. I've > been rsync'ing them to the data partition at the same time (yes, it's slow > because they are two partitions on the same array). The rsync aside, we've had > this workload going for a month on this particular server without any issues. > (The other server which is set up identically has been fine too.) On Monday, > we mkfs'd this server's sda4, mounted it as before and started the workload. What was the size of the log on the previous incarnation of the filesystem? > Then, on Tuesday and Wednesday, we saw two loadavg spikes for no apparent > reason. (Our system forks a bunch and then each child does network & disk I/O, > so 180 loadavg makes sense if the system gums up.) > > The following applies to all of the spikes, but I'm specifically talking about > the spike from this morning. During the ~45 minute spike, there seems to be > very little disk I/O (<1 MByte/s compared to the usual 10 MBytes/s). Since That sounds like it might have dropped into random 4k write IO or inode cluster RMW cycles - a single large RAID6 volume is going to be no faster than a single spindle at this. Can you get `iostat -d -m -x 5` output when the next slowdown occurs so we can see the IOPS and utilisation as well as the bandwidth? > all the I/O children get stuck waiting for disk (ps says they are in 'D' > state), the network utilization drops to essentially 0. The CPU usage also > drops to ~0%. > > I *think* things return to normal because our code eventually notices that > the children are stuck and it 'kill -9's them. (It's nicer at first.) you can't kill processes stuck waiting for log space IIRC. > > Also, getting the output of 'echo w > /proc/sysrq-trigger' whould be > > helpful here.... > > I assume you want this when the loadavg spikes up to 180. /me waits for the > next time it happens. Yup. Cheers, Dave. -- Dave Chinner david@xxxxxxxxxxxxx _______________________________________________ xfs mailing list xfs@xxxxxxxxxxx http://oss.sgi.com/mailman/listinfo/xfs
