On Thu, Jun 17, 2010 at 09:41:18AM +0800, Shaohua Li wrote: > On Mon, Jun 14, 2010 at 09:28:29PM +0800, Chris Mason wrote: > > On Sun, Jun 13, 2010 at 02:50:06PM +0800, Shaohua Li wrote: > > > On Fri, Jun 11, 2010 at 10:32:07AM +0800, Yan, Zheng wrote: > > > > On Fri, Jun 11, 2010 at 9:12 AM, Shaohua Li <shaohua.li@xxxxxxxxx> wrote: > > > > > On Fri, Jun 11, 2010 at 01:41:41AM +0800, Jerome Ibanes wrote: > > > > >> List, > > > > >> > > > > >> I ran into a hang issue (race condition: cpu is high when the server is > > > > >> idle, meaning that btrfs is hanging, and IOwait is high as well) running > > > > >> 2.6.34 on debian/lenny on a x86_64 server (dual Opteron 275 w/ 16GB ram). > > > > >> The btrfs filesystem live on 18x300GB scsi spindles, configured as Raid-0, > > > > >> as shown below: > > > > >> > > > > >> Label: none uuid: bc6442c6-2fe2-4236-a5aa-6b7841234c52 > > > > >> Total devices 18 FS bytes used 2.94TB > > > > >> devid 5 size 279.39GB used 208.33GB path /dev/cciss/c1d0 > > > > >> devid 17 size 279.39GB used 208.34GB path /dev/cciss/c1d8 > > > > >> devid 16 size 279.39GB used 209.33GB path /dev/cciss/c1d7 > > > > >> devid 4 size 279.39GB used 208.33GB path /dev/cciss/c0d4 > > > > >> devid 1 size 279.39GB used 233.72GB path /dev/cciss/c0d1 > > > > >> devid 13 size 279.39GB used 208.33GB path /dev/cciss/c1d4 > > > > >> devid 8 size 279.39GB used 208.33GB path /dev/cciss/c1d11 > > > > >> devid 12 size 279.39GB used 208.33GB path /dev/cciss/c1d3 > > > > >> devid 3 size 279.39GB used 208.33GB path /dev/cciss/c0d3 > > > > >> devid 9 size 279.39GB used 208.33GB path /dev/cciss/c1d12 > > > > >> devid 6 size 279.39GB used 208.33GB path /dev/cciss/c1d1 > > > > >> devid 11 size 279.39GB used 208.33GB path /dev/cciss/c1d2 > > > > >> devid 14 size 279.39GB used 208.33GB path /dev/cciss/c1d5 > > > > >> devid 2 size 279.39GB used 233.70GB path /dev/cciss/c0d2 > > > > >> devid 15 size 279.39GB used 209.33GB path /dev/cciss/c1d6 > > > > >> devid 10 size 279.39GB used 208.33GB path /dev/cciss/c1d13 > > > > >> devid 7 size 279.39GB used 208.33GB path /dev/cciss/c1d10 > > > > >> devid 18 size 279.39GB used 208.34GB path /dev/cciss/c1d9 > > > > >> Btrfs v0.19-16-g075587c-dirty > > > > >> > > > > >> The filesystem, mounted in /mnt/btrfs is hanging, no existing or new > > > > >> process can access it, however 'df' still displays the disk usage (3TB out > > > > >> of 5). The disks appear to be physically healthy. Please note that a > > > > >> significant number of files were placed on this filesystem, between 20 and > > > > >> 30 million files. > > > > >> > > > > >> The relevant kernel messages are displayed below: > > > > >> > > > > >> INFO: task btrfs-submit-0:4220 blocked for more than 120 seconds. > > > > >> "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. > > > > >> btrfs-submit- D 000000010042e12f 0 4220 2 0x00000000 > > > > >> ffff8803e584ac70 0000000000000046 0000000000004000 0000000000011680 > > > > >> ffff8803f7349fd8 ffff8803f7349fd8 ffff8803e584ac70 0000000000011680 > > > > >> 0000000000000001 ffff8803ff99d250 ffffffff8149f020 0000000081150ab0 > > > > >> Call Trace: > > > > >> [<ffffffff813089f3>] ? io_schedule+0x71/0xb1 > > > > >> [<ffffffff811470be>] ? get_request_wait+0xab/0x140 > > > > >> [<ffffffff810406f4>] ? autoremove_wake_function+0x0/0x2e > > > > >> [<ffffffff81143a4d>] ? elv_rq_merge_ok+0x89/0x97 > > > > >> [<ffffffff8114a245>] ? blk_recount_segments+0x17/0x27 > > > > >> [<ffffffff81147429>] ? __make_request+0x2d6/0x3fc > > > > >> [<ffffffff81145b16>] ? generic_make_request+0x207/0x268 > > > > >> [<ffffffff81145c12>] ? submit_bio+0x9b/0xa2 > > > > >> [<ffffffffa01aa081>] ? btrfs_requeue_work+0xd7/0xe1 [btrfs] > > > > >> [<ffffffffa01a5365>] ? run_scheduled_bios+0x297/0x48f [btrfs] > > > > >> [<ffffffffa01aa687>] ? worker_loop+0x17c/0x452 [btrfs] > > > > >> [<ffffffffa01aa50b>] ? worker_loop+0x0/0x452 [btrfs] > > > > >> [<ffffffff81040331>] ? kthread+0x79/0x81 > > > > >> [<ffffffff81003674>] ? kernel_thread_helper+0x4/0x10 > > > > >> [<ffffffff810402b8>] ? kthread+0x0/0x81 > > > > >> [<ffffffff81003670>] ? kernel_thread_helper+0x0/0x10 > > > > > This looks like the issue we saw too, http://lkml.org/lkml/2010/6/8/375. > > > > > This is reproduceable in our setup. > > > > > > > > I think I know the cause of http://lkml.org/lkml/2010/6/8/375. > > > > The code in the first do-while loop in btrfs_commit_transaction > > > > set current process to TASK_UNINTERRUPTIBLE state, then calls > > > > btrfs_start_delalloc_inodes, btrfs_wait_ordered_extents and > > > > btrfs_run_ordered_operations(). All of these function may call > > > > cond_resched(). > > > Hi, > > > When I test random write, I saw a lot of threads jump into btree_writepages() > > > and do noting and io throughput is zero for some time. Looks like there is a > > > live lock. See the code of btree_writepages(): > > > if (wbc->sync_mode == WB_SYNC_NONE) { > > > struct btrfs_root *root = BTRFS_I(mapping->host)->root; > > > u64 num_dirty; > > > unsigned long thresh = 32 * 1024 * 1024; > > > > > > if (wbc->for_kupdate) > > > return 0; > > > > > > /* this is a bit racy, but that's ok */ > > > num_dirty = root->fs_info->dirty_metadata_bytes; > > > >>>>>> if (num_dirty < thresh) > > > return 0; > > > } > > > The marked line is quite intrusive. In my test, the live lock is caused by the thresh > > > check. The dirty_metadata_bytes < 32M. Without it, I can't see the live lock. Not > > > sure if this is related to the hang. > > > > How much ram do you have? The goal of the check is to avoid writing > > metadata blocks because once we write them we have to do more IO to cow > > them again if they are changed later. > > > > It shouldn't be looping hard in btrfs there, what was the workload? > This is a fio randomwrite. Yep, I limited memory to a small size (~500M), because it makes > me easily to produce a 'xxx blocked for more than 120 seconds' issue. I can understand small > memory could be an issue, but this still looks intrusive, right? > > The issue Yanmin reported is under 2.6.35-rc1, so might not be the > 'TASK_UNINTERRUPTIBLE' issue, but we will try -rc3 too. I still get below message with 2.6.35-rc3. The system is still running, because my fio test finished even with the message. INFO: task flush-btrfs-134:14144 blocked for more than 120 seconds. "echo 0 > /proc/sys/kernel/hung_task_timeout_secs" disables this message. flush-btrfs-1 D 0000000100346d5c 4480 14144 2 0x00000000 ffff88016fd51530 0000000000000046 0000000000000001 ffff880100000000 ffff88023ef0f100 0000000000013ac0 0000000000013ac0 0000000000004000 0000000000013ac0 ffff88018be2dfd8 ffff88016fd51530 ffff88018be2dfd8 Call Trace: [<ffffffff8124be61>] ? wait_block_group_cache_progress+0xc0/0xe4 [<ffffffff81052977>] ? autoremove_wake_function+0x0/0x2a [<ffffffff81052977>] ? autoremove_wake_function+0x0/0x2a [<ffffffff8124f956>] ? find_free_extent+0x694/0x9c4 [<ffffffff8124fd53>] ? btrfs_reserve_extent+0xcd/0x189 [<ffffffff81262803>] ? cow_file_range+0x19e/0x2fc [<ffffffff81262fe0>] ? run_delalloc_range+0xa7/0x393 [<ffffffff8127832e>] ? test_range_bit+0x2b/0x127 [<ffffffff8127b44e>] ? find_lock_delalloc_range+0x1af/0x1d1 [<ffffffff8127b655>] ? __extent_writepage+0x1e5/0x61f [<ffffffff812c1fac>] ? prio_tree_next+0x1c0/0x221 [<ffffffff812bf3c8>] ? cpumask_any_but+0x28/0x37 [<ffffffff810b4af7>] ? page_mkclean+0x120/0x148 [<ffffffff8127bed2>] ? extent_write_cache_pages.clone.0+0x15e/0x26c [<ffffffff8127c0db>] ? extent_writepages+0x41/0x5a [<ffffffff81264319>] ? btrfs_get_extent+0x0/0x798 [<ffffffff810e6fcb>] ? writeback_single_inode+0xd1/0x2e8 [<ffffffff810e7d02>] ? writeback_inodes_wb+0x40d/0x51f [<ffffffff810e7f47>] ? wb_writeback+0x133/0x1b2 [<ffffffff810e81ae>] ? wb_do_writeback+0x148/0x15e [<ffffffff810e81fe>] ? bdi_writeback_task+0x3a/0x113 [<ffffffff81052897>] ? bit_waitqueue+0x14/0xa4 [<ffffffff810a9b19>] ? bdi_start_fn+0x0/0xc2 [<ffffffff810a9b7c>] ? bdi_start_fn+0x63/0xc2 [<ffffffff810a9b19>] ? bdi_start_fn+0x0/0xc2 [<ffffffff81052525>] ? kthread+0x75/0x7d [<ffffffff81003654>] ? kernel_thread_helper+0x4/0x10 [<ffffffff810524b0>] ? kthread+0x0/0x7d [<ffffffff81003650>] ? kernel_thread_helper+0x0/0x10 -- To unsubscribe from this list: send the line "unsubscribe linux-btrfs" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
