Re: how to debug slow rbd block device

[Mark Nelson <mark.nelson@inktank.com>]

On 5/23/12 2:22 AM, Andrey Korolyov wrote:
> Hi,
>
> For Stefan:
>
> Increasing socket memory gave me about some percents on fio tests
> inside VM(I have measured
> 'max-iops-until-ceph-throws-message-about-delayed-write' parameter).
> What is more important, osd process, if possible, should be pinned to
> dedicated core or two, and all other processes should not use this
> core(you may do it via cg or manually), because even one four-core
> non-pinned VM process during test causes a drop of osd` throughput
> almost twice, same for any other heavy process on the host.
Very interesting!  Thanks for sharing.

> net.core.rmem_max = 16777216
> net.core.wmem_max = 16777216
> net.ipv4.tcp_rmem = 4096 87380 16777216
> net.ipv4.tcp_wmem = 4096 65536 16777216
>
>
>
> On Wed, May 23, 2012 at 10:30 AM, Josh Durgin<josh.durgin@inktank.com>  wrote:
>> On 05/22/2012 11:18 PM, Stefan Priebe - Profihost AG wrote:
>>> Hi,
>>>
>>>>> So try enabling RBD writeback caching — see http://marc.info
>>>>> /?l=ceph-devel&m=133758599712768&w=2
>>>>> will test tomorrow. Thanks.
>>> Can we path this to the qemu-drive option?
>>
>> Yup, see http://article.gmane.org/gmane.comp.file-systems.ceph.devel/6400
>>
>> The normal qemu cache=writeback/writethrough/none option will work in qemu
>> 1.2.
>>
>> Josh
> By the way, is it possible to flush cache outside? I may need that for
> VM live migration and such hook will be helpful.
>
>
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