Re: MDS: cache pressure warnings with Ganesha exports

[Eugen Block <eblock@xxxxxx>]

Hi Felix,

we've had cache pressure messages for a long time in our small  
production cluster without seeing any negative impact to clients (or  
the cluster). We don't use Ganesha but we export CephFS directories  
via NFS. I guess NFS is the common denominator here.
In our case we started with a very low mds_cache_memory_limit value  
(around 2 or 4 GB, we also started with only a few clients) and  
increased it step by step, currently it is around 8 GB.

Cache status currently shows ~ 7.5 GB while top output shows 10.5 GB usage.

That seems to be enough for around 70 connected clients, although not  
all of them are constantly active.
So I would suggest to increase memory in small steps to see if those  
warnings go away.

Regards,
Eugen


Zitat von "Stolte, Felix" <f.stolte@xxxxxxxxxxxxx>:

> Hey folks,
>
> I  keep getting ceph health warnings about clients failing to  
> respond to cache pressure. They always refer to sessions from  
> ganesha exports. I've read all threads regarding this issue, but  
> none of my changes resolved it. What I’ve done so far:
>
> Ganesha.conf:
> MDCACHE {
>     Dir_Chunk = 0;
>     NParts = 1;
>     Cache_Size = 1;
> }
>
> Attr_Expiration_Time = 0 in every export
>
> mds_cache_memory_limit = 17179869184 on MDS Servers
>
> I even set “client_oc = false” on the ganesha server, but this  
> doesn’t seem to be applied
>
> My setup is ceph version 14.2.8 (All Server and clients. One active  
> MDS. Ganesha 2.8.3 runs on a dedicated Server.
>
> ceph daemon mds.<active_mds> dump_mempools (filtered out the empty pools):
>
> "mempool": {
>         "by_pool": {
>             "bloom_filter": {
>                 "items": 1414723,
>                 "bytes": 1414723
>             },
>             "buffer_anon": {
>                 "items": 180992,
>                 "bytes": 2404306271
>             },
>             "buffer_meta": {
>                 "items": 178660,
>                 "bytes": 15722080
>             },
>             "osdmap": {
>                 "items": 4121,
>                 "bytes": 75912
>             },
>       "mds_co": {
>                 "items": 221728924,
>                 "bytes": 16320868177
>             },
>         },
>         "total": {
>             "items": 223507420,
>             "bytes": 18742387163
>
>
> Every hint how to resolve the issue are welcome. If more information  
> is needed, I am glad to provide it.
>
> Regards Felix
>
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