Re: slow requests with rbd

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hi,

i've got following sysctl set:

kernel.perf_event_paranoid=2
kernel.watchdog_thresh=10
vm.min_free_kbytes=262144

could any of these configs cause the problem?

fous


2016-03-04 13:48 GMT+01:00 Max A. Krasilnikov <pseudo@xxxxxxxxxxxx>:
> Здравствуйте!
>
> On Fri, Mar 04, 2016 at 01:33:24PM +0100, honza801 wrote:
>
>> hi,
>
>> i have rbd0 mapped to client, xfs formatted. i'm putting a lot of data on it.
>> following messages appear in logs and 'ceph -s' output
>
>> osd.255 [WRN] 1 slow requests, 1 included below; oldest blocked for >
>> 51.726881 secs
>> osd.255 [WRN] slow request 51.726881 seconds old, received at
>> 2016-03-04 12:22:23.549737: osd_op(client.14296.1:389333
>> rbd_data.37d230c8153.00000000000d1cc8 [set-alloc-hint object_size
>> 4194304 write_size 4194304,writefull 0~4194304] 2.fc8c5908
>> ondisk+write e7523) currently waiting for subops from 120,239
>
>> it causes slow downs on writes. iostat, load, dmesg on osds shows nothing odd.
>
>> could anyone give me a hint?
>
> I spent a lot of time with this trouble because of "overtuning" of Linux TCP/IP
> stack using sysctl. If your disks are not overloaded, if your network is not
> overloaded, take a look on network configuration including sysctl.
>
> BTW, default sysctl settings are quite well :) Things can be better, but they
> are stable anough.
>
> --
> WBR, Max A. Krasilnikov
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