Messages in this thread | | | Date | Sun, 22 Jun 2008 21:56:17 +0100 | From | "Daniel J Blueman" <> | Subject | Re: [2.6.26-rc7] shrink_icache from pagefault locking (nee: nfsd hangs for a few sec)... |
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On Sun, Jun 22, 2008 at 7:21 PM, Arjan van de Ven <arjan@infradead.org> wrote: > On Sun, 22 Jun 2008 19:10:11 +0100 > Mel Gorman <mel@csn.ul.ie> wrote: > >> On (22/06/08 10:58), Daniel J Blueman didst pronounce: >> > I'm seeing a similar issue [2] to what was recently reported [1] by >> > Alexander, but with another workload involving XFS and memory >> > pressure. >> > >> >> Is NFS involved or is this XFS only? It looks like XFS-only but no >> harm in being sure. >> >> I'm beginning to wonder if this is a problem where a lot of dirty >> inodes are being written back in this path and we stall while that >> happens. I'm still not getting why we are triggering this now and did >> not before 2.6.26-rc1 or why it bisects to the zonelist >> modifications. Diffing the reclaim and allocation paths between >> 2.6.25 and 2.6.26-rc1 has not yielded any candidates for me yet that >> would explain this. > > this sort of thing can easily be exposed with the latencytop tool... > it will at least tell you WHAT the system is blocking on. > (not so much the why, the tool isn't smart enough to automatically spit > out kernel patches yet)
Good plan. I reproduced this without NFS mounted, so pure XFS. I wasn't able to capture the same process's (ie 5480) latencytop trace, but it may have contributed to the list.
A fair amount of debugging was turned on, hurting the latency some (despite it being a 3.6GHz Penryn).
Daniel
--- [1]
$ vmstat 1 procs -----------memory---------- ---swap-- -----io---- -system-- ----cpu---- r b swpd free buff cache si so bi bo in cs us sy id wa <snip> 1 1 156 14424 12 2329672 0 0 0 110755 177 3820 57 6 36 0 2 1 156 14736 12 2348152 0 0 24 25172 204 26018 35 21 43 1 5 0 156 24252 12 2363800 0 0 59656 31 545 25292 35 14 28 23 4 0 156 14696 12 2317784 0 0 3824 0 38 23083 95 6 0 0 4 0 156 14440 12 2319304 0 0 4672 0 72 3372 93 3 3 2 2 0 156 14428 12 2318484 0 0 0 4 27 731 52 0 49 0 2 0 156 14480 12 2308512 0 0 0 12 32 36629 39 13 49 0 2 0 156 14572 12 2301220 0 0 3904 12316 117 10760 58 7 26 11
--- [2]
Cause Maximum Percentage down xfs_buf_lock _xfs_buf_find xfs_buf_get_flags 271.1 msec 0.4 % down xfs_buf_iowait xfs_buf_iostart xfs_buf_read_f206.1 msec 1.3 % down xfs_buf_lock xfs_getsb xfs_trans_getsb xfs_tr160.4 msec 0.5 % sync_page sync_page_killable __lock_page_killable 155.3 msec 26.1 % down xfs_buf_iowait xfs_buf_iostart xfs_buf_read_f101.6 msec 0.6 % down xfs_buf_iowait xfs_buf_iostart xfs_buf_read_f 99.1 msec 0.7 % sync_page __lock_page find_lock_page filemap_fault 84.0 msec 1.5 % down xfs_buf_iowait xfs_buf_iostart xfs_buf_read_f 70.8 msec 0.4 % sync_buffer __wait_on_buffer __block_prepare_write 66.4 msec 0.1 % o_sync_readv_writev do_readv_writev vfs_writev
Process AutopanoPro (4697) Total: 4693.4 msec down xfs_buf_lock xfs_getsb xfs_trans_getsb xfs_tr126.2 msec 2.7 %trans_commit xfs_create xfs_vn_mknod xfs_vn_create vfs_create do_filp_open do_sys_open sync_page sync_page_killable __lock_page_killable 89.3 msec 15.3 %_read __xfs_file_read xfs_file_aio_read do_sync_read vfs_read sys_read system_call_after down xfs_buf_iowait xfs_buf_iostart xfs_buf_read_f 88.5 msec 2.2 %fs_da_do_buf xfs_da_read_buf xfs_dir2_leaf_lookup_int xfs_dir2_leaf_lookup xfs_dir_looku Scheduler: waiting for cpu 49.4 msec 77.7 % congestion_wait __alloc_pages_internal __alloc_pag 19.8 msec 1.4 %e_fault error_exit congestion_wait __alloc_pages_internal __alloc_pag 19.4 msec 0.4 %ead ondemand_readahead page_cache_async_readahead generic_file_aio_read xfs_read __xfs_f ile_read xfs_file_aio_read do_sync_read vfs_read
--- [3]
Cause Maximum Percentage sync_page sync_page_killable __lock_page_killable 103.9 msec 36.5 % Scheduler: waiting for cpu 37.0 msec 49.5 % sync_page __lock_page find_lock_page filemap_fault 28.6 msec 1.2 % congestion_wait __alloc_pages_internal __alloc_pag 19.5 msec 1.3 % congestion_wait __alloc_pages_internal __alloc_pag 19.2 msec 0.4 % congestion_wait __alloc_pages_internal __alloc_pag 19.2 msec 0.4 % do_page_fault error_exit d do_sync_read vfs_read 11.6 msec 0.5 % sys_mmap system_call_after_swapgs 7.8 msec 0.2 % do_select core_sys_select sys_select system_call_a 4.9 msec 8.1 %
Process AutopanoPro (4697) Total: 977.5 msec sync_page sync_page_killable __lock_page_killable 97.7 msec 76.6 %_read __xfs_file_read xfs_file_aio_read do_sync_read vfs_read sys_read system_call_after sync_page __lock_page find_lock_page filemap_fault 28.6 msec 5.6 %lt do_page_fault error_exit congestion_wait __alloc_pages_internal __alloc_pag 19.5 msec 2.0 %e_fault error_exit congestion_wait __alloc_pages_internal __alloc_pag 19.2 msec 2.0 %k_write_begin xfs_vm_write_begin generic_file_buffered_write xfs_write __xfs_file_write Scheduler: waiting for cpu_write vfs_write 16.5 msec 8.7 % do_page_fault error_exit 11.6 msec 2.3 %
--- [4]
======================================================= [ INFO: possible circular locking dependency detected ] 2.6.26-rc7-211c #2 ------------------------------------------------------- AutopanoPro/5480 is trying to acquire lock: (iprune_mutex){--..}, at: [<ffffffff802d2a5d>] shrink_icache_memory+0x7d/0x280
but task is already holding lock: (&(&ip->i_iolock)->mr_lock){----}, at: [<ffffffff803a459f>] xfs_ilock+0xbf/0x110
which lock already depends on the new lock.
the existing dependency chain (in reverse order) is:
-> #1 (&(&ip->i_iolock)->mr_lock){----}: [<ffffffff802769ad>] __lock_acquire+0xbdd/0x1020 [<ffffffff80276e55>] lock_acquire+0x65/0x90 [<ffffffff8026b41b>] down_write_nested+0x4b/0x90 [<ffffffff803a45df>] xfs_ilock+0xff/0x110 [<ffffffff803a47af>] xfs_ireclaim+0x3f/0x90 [<ffffffff803c9169>] xfs_finish_reclaim+0x59/0x220 [<ffffffff803cc3b5>] xfs_reclaim+0x185/0x190 [<ffffffff803d9211>] xfs_fs_clear_inode+0xe1/0x130 [<ffffffff802d25c7>] clear_inode+0x87/0x120 [<ffffffff802d290a>] dispose_list+0x2a/0x100 [<ffffffff802d2c06>] shrink_icache_memory+0x226/0x280 [<ffffffff8029d9c5>] shrink_slab+0x125/0x180 [<ffffffff8029dc52>] try_to_free_pages+0x232/0x360 [<ffffffff80297f0d>] __alloc_pages_internal+0x1ed/0x4a0 [<ffffffff802981db>] __alloc_pages+0xb/0x10 [<ffffffff802a312a>] handle_mm_fault+0x46a/0x6d0 [<ffffffff8060510a>] do_page_fault+0x3ca/0x830 [<ffffffff80602add>] error_exit+0x0/0xa9 [<ffffffffffffffff>] 0xffffffffffffffff
-> #0 (iprune_mutex){--..}: [<ffffffff80276817>] __lock_acquire+0xa47/0x1020 [<ffffffff80276e55>] lock_acquire+0x65/0x90 [<ffffffff8060059a>] mutex_lock_nested+0xba/0x2b0 [<ffffffff802d2a5d>] shrink_icache_memory+0x7d/0x280 [<ffffffff8029d9c5>] shrink_slab+0x125/0x180 [<ffffffff8029dc52>] try_to_free_pages+0x232/0x360 [<ffffffff80297f0d>] __alloc_pages_internal+0x1ed/0x4a0 [<ffffffff802981db>] __alloc_pages+0xb/0x10 [<ffffffff8029a6b6>] __do_page_cache_readahead+0x136/0x230 [<ffffffff8029aa08>] ondemand_readahead+0x128/0x1f0 [<ffffffff8029ab45>] page_cache_async_readahead+0x75/0xa0 [<ffffffff80293a8a>] generic_file_aio_read+0x28a/0x610 [<ffffffff803d78c4>] xfs_read+0x124/0x270 [<ffffffff803d4416>] __xfs_file_read+0x46/0x50 [<ffffffff803d4451>] xfs_file_aio_read+0x11/0x20 [<ffffffff802bc1b1>] do_sync_read+0xf1/0x130 [<ffffffff802bca74>] vfs_read+0xc4/0x160 [<ffffffff802bcf10>] sys_read+0x50/0x90 [<ffffffff8022639b>] system_call_after_swapgs+0x7b/0x80 [<ffffffffffffffff>] 0xffffffffffffffff
other info that might help us debug this:
2 locks held by AutopanoPro/5480: #0: (&(&ip->i_iolock)->mr_lock){----}, at: [<ffffffff803a459f>] xfs_ilock+0xbf/0x110 #1: (shrinker_rwsem){----}, at: [<ffffffff8029d8d2>] shrink_slab+0x32/0x180
stack backtrace: Pid: 5480, comm: AutopanoPro Not tainted 2.6.26-rc7-211c #2
Call Trace: [<ffffffff80274293>] print_circular_bug_tail+0x83/0x90 [<ffffffff80276817>] __lock_acquire+0xa47/0x1020 [<ffffffff8027588f>] ? trace_hardirqs_on+0xbf/0x150 [<ffffffff80276e55>] lock_acquire+0x65/0x90 [<ffffffff802d2a5d>] ? shrink_icache_memory+0x7d/0x280 [<ffffffff8060059a>] mutex_lock_nested+0xba/0x2b0 [<ffffffff802d2a5d>] ? shrink_icache_memory+0x7d/0x280 [<ffffffff80602915>] ? _spin_unlock_irqrestore+0x55/0x60 [<ffffffff802d2a5d>] shrink_icache_memory+0x7d/0x280 [<ffffffff8029d8d2>] ? shrink_slab+0x32/0x180 [<ffffffff8029d9c5>] shrink_slab+0x125/0x180 [<ffffffff8029dc52>] try_to_free_pages+0x232/0x360 [<ffffffff8029c570>] ? isolate_pages_global+0x0/0x40 [<ffffffff80297f0d>] __alloc_pages_internal+0x1ed/0x4a0 [<ffffffff802981db>] __alloc_pages+0xb/0x10 [<ffffffff8029a6b6>] __do_page_cache_readahead+0x136/0x230 [<ffffffff8029aa08>] ondemand_readahead+0x128/0x1f0 [<ffffffff8029ab45>] page_cache_async_readahead+0x75/0xa0 [<ffffffff80293a8a>] generic_file_aio_read+0x28a/0x610 [<ffffffff803d78c4>] xfs_read+0x124/0x270 [<ffffffff803d4416>] __xfs_file_read+0x46/0x50 [<ffffffff803d4451>] xfs_file_aio_read+0x11/0x20 [<ffffffff802bc1b1>] do_sync_read+0xf1/0x130 [<ffffffff802673f0>] ? autoremove_wake_function+0x0/0x40 [<ffffffff8022ce57>] ? native_sched_clock+0x57/0x80 [<ffffffff802bda68>] ? fget_light+0xe8/0x100 [<ffffffff80272dea>] ? lock_release_holdtime+0x5a/0x80 [<ffffffff802bca74>] vfs_read+0xc4/0x160 [<ffffffff802bcf10>] sys_read+0x50/0x90 [<ffffffff8022639b>] system_call_after_swapgs+0x7b/0x80 -- Daniel J Blueman
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