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| author | Theodore Ts'o <tytso@mit.edu> | 2013-04-21 16:47:54 -0400 |
|---|---|---|
| committer | Theodore Ts'o <tytso@mit.edu> | 2013-04-21 16:47:54 -0400 |
| commit | f783f091e49ce4896e6b026af82d76e0537c6089 (patch) | |
| tree | 0ff78a05254d4b996bb027d9fac9969d1d6e0b07 | |
| parent | 13fca323e9a8b63c08de7a4e05d3c702516b535d (diff) | |
| download | linux-f783f091e49ce4896e6b026af82d76e0537c6089.tar.bz2 | |
jbd2: trace when lock_buffer in do_get_write_access takes a long time
While investigating interactivity problems it was clear that processes
sometimes stall for long periods of times if an attempt is made to
lock a buffer which is undergoing writeback. It would stall in
a trace looking something like
[<ffffffff811a39de>] __lock_buffer+0x2e/0x30
[<ffffffff8123a60f>] do_get_write_access+0x43f/0x4b0
[<ffffffff8123a7cb>] jbd2_journal_get_write_access+0x2b/0x50
[<ffffffff81220f79>] __ext4_journal_get_write_access+0x39/0x80
[<ffffffff811f3198>] ext4_reserve_inode_write+0x78/0xa0
[<ffffffff811f3209>] ext4_mark_inode_dirty+0x49/0x220
[<ffffffff811f57d1>] ext4_dirty_inode+0x41/0x60
[<ffffffff8119ac3e>] __mark_inode_dirty+0x4e/0x2d0
[<ffffffff8118b9b9>] update_time+0x79/0xc0
[<ffffffff8118ba98>] file_update_time+0x98/0x100
[<ffffffff81110ffc>] __generic_file_aio_write+0x17c/0x3b0
[<ffffffff811112aa>] generic_file_aio_write+0x7a/0xf0
[<ffffffff811ea853>] ext4_file_write+0x83/0xd0
[<ffffffff81172b23>] do_sync_write+0xa3/0xe0
[<ffffffff811731ae>] vfs_write+0xae/0x180
[<ffffffff8117361d>] sys_write+0x4d/0x90
[<ffffffff8159d62d>] system_call_fastpath+0x1a/0x1f
[<ffffffffffffffff>] 0xffffffffffffffff
Signed-off-by: Mel Gorman <mgorman@suse.de>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>
| -rw-r--r-- | fs/jbd2/transaction.c | 8 | ||||
| -rw-r--r-- | include/trace/events/jbd2.h | 21 |
2 files changed, 29 insertions, 0 deletions
diff --git a/fs/jbd2/transaction.c b/fs/jbd2/transaction.c index a1920da22802..10f524c59ea8 100644 --- a/fs/jbd2/transaction.c +++ b/fs/jbd2/transaction.c @@ -639,6 +639,7 @@ do_get_write_access(handle_t *handle, struct journal_head *jh, int error; char *frozen_buffer = NULL; int need_copy = 0; + unsigned long start_lock, time_lock; if (is_handle_aborted(handle)) return -EROFS; @@ -654,9 +655,16 @@ repeat: /* @@@ Need to check for errors here at some point. */ + start_lock = jiffies; lock_buffer(bh); jbd_lock_bh_state(bh); + /* If it takes too long to lock the buffer, trace it */ + time_lock = jbd2_time_diff(start_lock, jiffies); + if (time_lock > HZ/10) + trace_jbd2_lock_buffer_stall(bh->b_bdev->bd_dev, + jiffies_to_msecs(time_lock)); + /* We now hold the buffer lock so it is safe to query the buffer * state. Is the buffer dirty? * diff --git a/include/trace/events/jbd2.h b/include/trace/events/jbd2.h index 070df49e4a1d..c1d1f3eb242d 100644 --- a/include/trace/events/jbd2.h +++ b/include/trace/events/jbd2.h @@ -358,6 +358,27 @@ TRACE_EVENT(jbd2_write_superblock, MINOR(__entry->dev), __entry->write_op) ); +TRACE_EVENT(jbd2_lock_buffer_stall, + + TP_PROTO(dev_t dev, unsigned long stall_ms), + + TP_ARGS(dev, stall_ms), + + TP_STRUCT__entry( + __field( dev_t, dev ) + __field(unsigned long, stall_ms ) + ), + + TP_fast_assign( + __entry->dev = dev; + __entry->stall_ms = stall_ms; + ), + + TP_printk("dev %d,%d stall_ms %lu", + MAJOR(__entry->dev), MINOR(__entry->dev), + __entry->stall_ms) +); + #endif /* _TRACE_JBD2_H */ /* This part must be outside protection */ |