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

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Date:	Fri, 17 Oct 2014 16:29:29 +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 #2 from Markus Königshaus <m.koenigshaus@....de> ---
Hi Theodore,

even after a very long wait, the performance remain so low. The performance is
also low when you copy files. I have used dd, so I create only reproducible
write access.
I have now tested the ext3 FS, same result.

After some debugging I found out, there is a delay in start_this_handle (look
at the timing), with echo 5 > /sys/kernel/debug/jbd/jbd-debug I get:

>> before mysqlshutdown:
...
[   40.400755] fs/jbd/transaction.c: (journal_stop, 1380): h_ref 2 -> 1
[   40.400755] 
[   40.400765] fs/jbd/transaction.c: (journal_stop, 1384): Handle df03e000
going down
[   40.400765] 
[   40.400789] fs/jbd/transaction.c: (journal_start, 290): from journal_start
[   40.400789] 
[   40.400801] fs/jbd/transaction.c: (start_this_handle, 110): New handle
df03e000 going live.
[   40.400801] 
[   40.400813] fs/jbd/transaction.c: (start_this_handle, 229): Handle df03e000
given 14 credits (total 21, free 14286)
...

>> after mysqlshutdown:
...
[   61.383886] fs/jbd/transaction.c: (journal_stop, 1380): h_ref 2 -> 1
[   61.383886] 
[   61.383896] fs/jbd/transaction.c: (journal_stop, 1384): Handle df03e000
going down
[   61.383896] 
[   61.393528] fs/jbd/transaction.c: (start_this_handle, 110): New handle
df03e000 going live.
[   61.393528] 
[   61.393541] fs/jbd/transaction.c: (start_this_handle, 229): Handle df03e000
given 14 credits (total 21, free 14271)
...

I try to isolate the problem in more detail next week, I would welcome tips and
help for my try.

Regards, Markus

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