linux-ext4 - [Bug 86471] drastic reduction of write performance after the termination of mysqld

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Date:	Wed, 22 Oct 2014 16:00:51 +0000
From:	bugzilla-daemon@...zilla.kernel.org
To:	linux-ext4@...r.kernel.org
Subject: [Bug 86471] drastic reduction of write performance after the
 termination of mysqld

https://bugzilla.kernel.org/show_bug.cgi?id=86471

--- Comment #3 from Markus Königshaus <m.koenigshaus@....de> ---
It looks like a problem in the writeback - mechanism, not ext4 related, sorry:

cd /sys/kernel/debug/tracing/
echo function > current_tracer
echo writeback* > set_ftrace_filter

>> before mysqlshutdown

# tracer: function
#
# entries-in-buffer/entries-written: 3/3   #P:1
#
#                              _-----=> irqs-off
#                             / _----=> need-resched
#                            | / _---=> hardirq/softirq
#                            || / _--=> preempt-depth
#                            ||| /     delay
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#              | |       |   ||||       |         |
              dd-3666  [000] ...1  1338.484467: writeback_in_progress
<-balance_dirty_pages_ratelimited
    kworker/u2:2-1001  [000] ...2  1338.557118: writeback_sb_inodes
<-__writeback_inodes_wb
    kworker/u2:2-1001  [000] ...2  1338.557160: writeback_sb_inodes
<-__writeback_inodes_wb

>> after mysqlshutdown:
# tracer: function
#
# entries-in-buffer/entries-written: 384/384   #P:1
#
#                              _-----=> irqs-off
#                             / _----=> need-resched
#                            | / _---=> hardirq/softirq
#                            || / _--=> preempt-depth
#                            ||| /     delay
#           TASK-PID   CPU#  ||||    TIMESTAMP  FUNCTION
#              | |       |   ||||       |         |
              dd-3733  [000] ...1  1403.061232: writeback_in_progress
<-balance_dirty_pages_ratelimited
    kworker/u2:2-1001  [000] ...2  1403.061277: writeback_sb_inodes
<-__writeback_inodes_wb
              dd-3733  [000] ...1  1403.071042: writeback_in_progress
<-balance_dirty_pages_ratelimited
              dd-3733  [000] ...1  1403.071328: writeback_in_progress
<-balance_dirty_pages_ratelimited
    kworker/u2:2-1001  [000] ...2  1403.071350: writeback_sb_inodes
<-__writeback_inodes_wb
              dd-3733  [000] ...1  1403.077546: writeback_in_progress
<-balance_dirty_pages_ratelimited

[ ... repeat 368 times ... ]

              dd-3733  [000] ...1  1404.327043: writeback_in_progress
<-balance_dirty_pages_ratelimited
              dd-3733  [000] ...1  1404.327306: writeback_in_progress
<-balance_dirty_pages_ratelimited
    kworker/u2:2-1001  [000] ...2  1404.327336: writeback_sb_inodes
<-__writeback_inodes_wb
              dd-3733  [000] ...1  1404.337125: writeback_in_progress
<-balance_dirty_pages_ratelimited

someone an idea, where to report this problem?

Regards, Markus

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