Hi,
I check all my ceph servers and they are not mount cephfs on each of them(maybe I umount after testing). As a result, the cluster didn't encounter a memory deadlock. Besides, I check the monitoring system and the memory and cpu usage were at common level while the clients hung.
Back to my question, there must be something else cause the client hang.
Zhenshi Zhou <deaderzzs@xxxxxxxxx> 于2018年8月8日周三 上午4:16写道：
Hi, I'm not sure if it just mounts the cephfs without using or doing any operation within the mounted directory would be affected by flushing cache. I mounted cephfs on osd servers only for testing and then left it there. Anyway I will umount it.ThanksJohn Spray <jspray@xxxxxxxxxx>于2018年8月8日 周三03:37写道：On Tue, Aug 7, 2018 at 5:42 PM Reed Dier <reed.dier@xxxxxxxxxxx> wrote:
>
> This is the first I am hearing about this as well.
This is not a Ceph-specific thing -- it can also affect similar
systems like Lustre.
The classic case is when under some memory pressure, the kernel tries
to free memory by flushing the client's page cache, but doing the
flush means allocating more memory on the server, making the memory
pressure worse, until the whole thing just seizes up.
John
> Granted, I am using ceph-fuse rather than the kernel client at this point, but that isn’t etched in stone.
>
> Curious if there is more to share.
>
> Reed
>
> On Aug 7, 2018, at 9:47 AM, Webert de Souza Lima <webert.boss@xxxxxxxxx> wrote:
>
>
> Yan, Zheng <ukernel@xxxxxxxxx> 于2018年8月7日周二 下午7:51写道：
>>
>> On Tue, Aug 7, 2018 at 7:15 PM Zhenshi Zhou <deaderzzs@xxxxxxxxx> wrote:
>> this can cause memory deadlock. you should avoid doing this
>>
>> > Yan, Zheng <ukernel@xxxxxxxxx>于2018年8月7日 周二19:12写道：
>> >>
>> >> did you mount cephfs on the same machines that run ceph-osd?
>> >>
>
>
> I didn't know about this. I run this setup in production. :P
>
> Regards,
>
> Webert Lima
> DevOps Engineer at MAV Tecnologia
> Belo Horizonte - Brasil
> IRC NICK - WebertRLZ
>
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