Re: [Qemu-devel] 回复： 回复： 回复： qemu vm big network latency when met heavy io

[Josh Durgin <josh.durgin@inktank.com>]

On 01/12/2014 06:39 PM, Stefan Hajnoczi wrote:
> On Fri, Jan 10, 2014 at 11:50 AM, 叶绍琛 <yeshaochen@foxmail.com> wrote:
> 
> Please use Reply-all to keep the CC list in tact.  That way the
> conversation stays on the mailing list and others can participate.
> 
>>> Is the sum of guests' RAM less than the total physical RAM on the host
>> The host run 3 vms, each vm use one vcpu core and 1G ram.
>> # free -m
>>
>>               total       used       free     shared    buffers     cached
>>
>> Mem:         32242       4808      27434          0        278       2058
>>
>> -/+ buffers/cache:       2471      29771
>>
>> Swap:         4095          0       4095
>>
>>
>> The host has 8 cores.
>> # cat /proc/cpuinfo | grep processor
>> processor : 0
>> processor : 1
>> processor : 2
>> processor : 3
>> processor : 4
>> processor : 5
>> processor : 6
>> processor : 7
>>
>> so, both of two question's answer is 'yes'.
>> When I runing random write test, the host use 0 swap.
> 
> Great.  That means the host is not overcommitted.
> 
> It's likely that the problem is a bug in QEMU's rbd driver or librados.
> 
> Josh: Perhaps something you're interested in looking into?

Yes, thanks for bringing it to my attention. It does sound like a bug in
QEMU's rbd driver or ceph's userspace libraries.

Could you share what version of librbd you're using, and your
/etc/ceph/ceph.conf?

Thanks,
Josh