From mboxrd@z Thu Jan 1 00:00:00 1970
From: bugzilla-daemon@bugzilla.kernel.org
Subject: [Bug 78651] Write performance of ext4 degrades linearly as volume
fills
Date: Sun, 22 Jun 2014 23:18:10 +0000
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--- Comment #2 from Joseph D. Wagner ---
I changed the script to run "perf record" on the dump command. I turned
tracing on for all jbd2 and ext4 events. (I had to stop it about half way
through, because the perf.data file was getting too big.) All non-zero results
are below.
Are some of these events supposed to be balanced? For example, there were 8
ext4:ext4_es_shrink_enter, but 0 ext4:ext4_es_shrink_exit. I'm wondering if
some of this code is being called recursively without proper unwinding. It
could explain the recursive loss in performance.
499M ext4:ext4_journal_start: 356 chunks LOST!
252M jbd2:jbd2_handle_stats: 4 chunks LOST!
252M jbd2:jbd2_handle_start: 1 chunks LOST!
252M ext4:ext4_mark_inode_dirty: 3 chunks LOST!
246M ext4:ext4_ext_show_extent: 1 chunks LOST!
246M ext4:ext4_ext_map_blocks_exit: 1 chunks LOST!
246M ext4:ext4_ext_map_blocks_enter: 26 chunks LOST!
246M ext4:ext4_es_lookup_extent_exit
246M ext4:ext4_es_lookup_extent_enter: 1 chunks LOST!
246M ext4:ext4_es_insert_extent
246M ext4:ext4_da_write_end: 6 chunks LOST!
246M ext4:ext4_da_write_begin: 441 chunks LOST!
246M ext4:ext4_da_reserve_space
150 ext4:ext4_drop_inode
77 ext4:ext4_releasepage
17 ext4:ext4_es_cache_extent
8 ext4:ext4_sync_fs
8 ext4:ext4_es_shrink_enter
5 ext4:ext4_es_find_delayed_extent_range_exit
5 ext4:ext4_es_find_delayed_extent_range_enter
3 ext4:ext4_request_inode
3 ext4:ext4_allocate_inode
2 ext4:ext4_ext_load_extent
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