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flush-btrfs-1 doing 1MiB/s (avg) writing on idle system??

DISCUSSION marcel partap 1 participant 1 message Aug 4, 2010 Btrfs file system

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Dear BTRFS devs,
still trying to find the cause for https://bugzilla.kernel.org/show_bug.cgi?id=12309 i stumbled over the strange fact that the flush-btrfs-1 thread is writing about 1MiBps constantly onto my root fs, even after turning off io-prone BOINC and NTOP.. there are other threads doing minor IO but that seems unrelated. My kernel is

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Linux handtuch 2.6.35 #1 SMP PREEMPT Mon Aug 2 13:55:56 CEST 2010 x86_64 AMD Phenom(tm) II X4 920 Processor AuthenticAMD GNU/Linux

with patch #488 from mentioned bug report applied. The partition is mounted

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/dev/root on / type btrfs (rw,noatime,noacl)

and btrfs filesystem show /dev/sda2 gives

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Label: none uuid: 50719157-1813-4552-bcd5-65f85649e503
Total devices 1 FS bytes used 230.12GB
devid 1 size 465.58GB used 335.29GB path /dev/sda2
Btrfs v0.19-16-g075587c-dirty

I have uploaded an archived blktrace for about 10 minutes at
http://hfopi.org/files/temp/btrfs-blktrace-idle.tar.bz2 (18M)
and the resulting diagram is
http://hfopi.org/files/temp/btrfs-blktrace-idle-trace.png
As i couldn't find an easy way to see what actually is located at these blocknumbers i am now kindly asking for assistance here - can anyone make any sense out of this? It surely makes me feel a lil' uncomfortable about my system's kosherness.. best regards,
marcel ;)