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

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Message-ID: <bug-86471-13602-ApLc0iLpJM@https.bugzilla.kernel.org/>
Date:	Thu, 23 Oct 2014 16:36:01 +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 #6 from Markus Königshaus <m.koenigshaus@....de> ---

I think I have found the error. The kernel calls apparently for the same page
dec_zone_page_state on (page, NR_FILE_DIRTY) twice, which means that the dirty
page counter underflows (is getting negative): 

cat /proc/meminfo 
MemTotal:         511492 kB
MemFree:          406972 kB
MemAvailable:     450536 kB
Buffers:            1840 kB
Cached:            52140 kB
SwapCached:            0 kB
Active:            54348 kB
Inactive:          34456 kB
Active(anon):      34904 kB
Inactive(anon):     5440 kB
Active(file):      19444 kB
Inactive(file):    29016 kB
Unevictable:           0 kB
Mlocked:               0 kB
HighTotal:             0 kB
HighFree:              0 kB
LowTotal:         511492 kB
LowFree:          406972 kB
SwapTotal:             0 kB
SwapFree:              0 kB
>> Dirty:          4294967148 kB
Writeback:             0 kB
AnonPages:         34844 kB
Mapped:            13992 kB
Shmem:              5520 kB
Slab:               9196 kB
SReclaimable:       4976 kB
SUnreclaim:         4220 kB
KernelStack:         696 kB
PageTables:         1024 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:      255744 kB
Committed_AS:     365452 kB
VmallocTotal:     499712 kB
VmallocUsed:        3512 kB
VmallocChunk:     495964 kB

The writeback - mechanism thinks that too much pages are dirty and disables the
writeback - cache.

Who can I send this bug?
Markus

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