Carlos Carvalho wrote:
Neil Brown (neilb@xxxxxxx) wrote on 21 January 2008 12:15:
>On Sunday January 20, carlos@xxxxxxxxxxxxxx wrote:
>> A raid6 array with a spare and bitmap is idle: not mounted and with no
>> IO to it or any of its disks (obviously), as shown by iostat. However
>> it's consuming cpu: since reboot it used about 11min in 24h, which is quite
>> a lot even for a busy array (the cpus are fast). The array was cleanly
>> shutdown so there's been no reconstruction/check or anything else.
>>
>> How can this be? Kernel is 2.6.22.16 with the two patches for the
>> deadlock ("[PATCH 004 of 4] md: Fix an occasional deadlock in raid5 -
>> FIX") and the previous one.
>
>Maybe the bitmap code is waking up regularly to do nothing.
>
>Would you be happy to experiment? Remove the bitmap with
> mdadm --grow /dev/mdX --bitmap=none
>
>and see how that affects cpu usage?
Confirmed, removing the bitmap stopped cpu consumption.
Looks like quite a bit of CPU going into idle arrays here, too.
--
Bill Davidsen <davidsen@xxxxxxx>
"Woe unto the statesman who makes war without a reason that will still
be valid when the war is over..." Otto von Bismark
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