[Lustre-discuss] MDS memory usage

[Frederik Ferner]

Hi Bernd,

thanks for your reply.

Bernd Schubert wrote:
> On Tuesday, August 24, 2010, Frederik Ferner wrote:
>> on our MDS we noticed that all memory seems to be used. (And it's not
>> just normal buffers/cache as far as I can tell.)
>>
>> When we put load on the machine, for example by starting rsync
>> on a few clients, generating file lists to copy data from Lustre to
>> local disks or just running a MDT backup locally using dd/gzip to copy a
>> LVM snapshot to a remote server, kswapd starts using a lot of CPU
>> time, sometimes up to 100% of one CPU core.
>>
>> This is on a Lustre 1.6.7.2.ddn3.5 based file system with about 200TB,
>> the MDT is 800GB with 200M inodes, ACLs enabled.
> 
> Did you recompile it, or did you use the binaries from my home page (or those 
> you got from CV)?

This is a recompiled Lustre version to include the patch from bug   	 22820.

> Possibly it is a LRU auto-resize problem, but which has been disabled in DDN 
> builds. As our 1.6 releases didn't include a patch for that, you would need to 
> specify the correct command options if you recompiled it.

I guess it's likely that I have not specified the correct option. So the 
  binaries on your home page are compiled with '--disable-lru-resize'? 
Any other options that you used?

> Another reason might be bug 22771, although that should only come up on MDS 
> with more memory you have.

I had a look at that bug and while we have a default stripe count of 1 
so the stripe count should fit into the inode. On the other hand we use 
ACLs in quite a few places, so it seems we might hit this bug if we 
increase the memory from the 16GB currently, correct?

Cheers,
Frederik
-- 
Frederik Ferner
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