Re: VM issue causing high CPU loads

Yohan
2009-09-03T13:39:40Z

>>> I did only:
>>>
>>> --- linux-2.6.27.21/include/linux/sunrpc/auth.h 2009-03-23 23:04:09.000000000 +0100
>>> +++ linux-2.6.27.21/include/linux/sunrpc/auth.h 2009-05-19 16:02:35.000000000 +0200
>>> @@ -62,8 +62,12 @@
>>> */
>>> - #define RPC_CREDCACHE_HASHBITS 4
>>> + #define RPC_CREDCACHE_HASHBITS 12
>>>
>>>
>>> And i test it in prod since sunday: i only have 36% of one core used by
>>> system
>>> versus more than 3 cores used by system in another server that did a
>>> drop_caches at morning...
>>>
>> OK, but it's still pretty bad. Let's tell the NFS guys.
>>
>> In http://bugzilla.kernel.org/show_bug.cgi?id=14024 we appear to have a
>> major meltdown caused by the linear search in
>> rpcauth_lookup_credcache() with Yohan's workload.
>>
> OK. Could we please have some more details about the actual workload involved here?
>
I add a new server CPU graph and 60s readprofile on the bugzilla

> As far as I can see, there is no RPCSEC_GSS involved, so credentials
> should never expire. They will be reused as long as processes aren't
> switching between thousands and thousands of different combinations of
> uid, gid and groups.
My servers are imap servers.
Foreach user (~15 million) it have a specific uid over ~10 nfs netapp
storage.