Re: CephFS mds cache pressure

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I have the same issues with the variety of kernel clients running 4.6.3 and 4.4.12 and fuse clients from 10.2.2.

-Mykola

-----Original Message-----
From: xiaoxi chen <superdebugger@xxxxxxxxxxx>
To: João Castro <castrofjoao@xxxxxxxxx>, ceph-users@xxxxxxxxxxxxxx <ceph-users@xxxxxxxxxxxxxx>
Subject: Re: CephFS mds cache pressure
Date: Wed, 29 Jun 2016 01:00:40 +0000

Hmm, I asked in the ML some days before,:) likely you hit the kernel bug which fixed by commit 5e804ac482 "ceph: don't invalidate page cache when inode is no longer used”.  This fix is in 4.4 but not in 4.2. I haven't got a chance to play with 4.4 , it would be great if you can have a try.

For MDS OOM issue, we did a MDS RSS vs #Inodes scaling test, the result showing around 4MB per 1000 Inodes, so your MDS likely can hold up to 2~3 Million inodes. But yes, even with the fix if the client misbehavior (open and hold a lot of inodes, doesn't respond to cache pressure message), MDS can go over the throttling and then killed by OOM


> To: ceph-users@xxxxxxxxxxxxxx
> From: castrofjoao@xxxxxxxxx
> Date: Tue, 28 Jun 2016 21:34:03 +0000
> Subject: Re: [ceph-users] CephFS mds cache pressure
>
> Hey John,
>
> ceph version 10.2.2 (45107e21c568dd033c2f0a3107dec8f0b0e58374)
> 4.2.0-36-generic
>
> Thanks!
>
> _______________________________________________
> ceph-users mailing list
> ceph-users@xxxxxxxxxxxxxx
> http://lists.ceph.com/listinfo.cgi/ceph-users-ceph.com
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