Yan, Zheng e30b5dca15 ext4: fix fio regression ... We (Linux Kernel Performance project) found a regression introduced by commit: f7fec032aa ext4: track all extent status in extent status tree The commit causes about 20% performance decrease in fio random write test. Profiler shows that rb_next() uses a lot of CPU time. The call stack is: rb_next ext4_es_find_delayed_extent ext4_map_blocks _ext4_get_block ext4_get_block_write __blockdev_direct_IO ext4_direct_IO generic_file_direct_write __generic_file_aio_write ext4_file_write aio_rw_vect_retry aio_run_iocb do_io_submit sys_io_submit system_call_fastpath io_submit td_io_getevents io_u_queued_complete thread_main main __libc_start_main The cause is that ext4_es_find_delayed_extent() doesn't have an upper bound, it keeps searching until a delayed extent is found. When there are a lots of non-delayed entries in the extent state tree, ext4_es_find_delayed_extent() may uses a lot of CPU time. Reported-by: LKP project <lkp@linux.intel.com> Signed-off-by: Yan, Zheng <zheng.z.yan@intel.com> Signed-off-by: Zheng Liu <wenqing.lz@taobao.com> Cc: "Theodore Ts'o" <tytso@mit.edu>		2013-05-03 02:15:52 -04:00
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events	ext4: fix fio regression	2013-05-03 02:15:52 -04:00
define_trace.h	treewide: fix comment/printk/variable typos	2012-09-01 10:33:05 -07:00
ftrace.h	tracing: Kill unused and puzzled sample code in ftrace.h	2012-11-13 15:51:21 -05:00
syscall.h	tracing: Cleanup unnecessary function declarations	2012-10-31 16:45:34 -04:00