[Lustre-discuss] collectl

[Kilian CAVALOTTI]

Hi Mark,

> useful. I suppose one might also make that argument about things like
> statfs, getattr - the only time I was able to make them change was in
> response to lfs commands. Might that logic also be applied to
> extended attributes and acl counters which I suspect also fall into
> the category of slowly changing counters?  

If you have ACLs enabled on your MDS, then every "ls -l" will induce 
getxattr()s and the mds_getxattr counter will be increased by as much. 
So this can change quickly. mds_setxattr, on the other hand, may change 
less often, since you usually set ACLs less often than you list files. 
But it can still be interesting to see if mds_setxattr goes through the 
roof.

> On the other hand, it seems like the 'reint' counters are the ones
> that tend to change a lot. Perhaps a clue is they're all prefaced
> with reint which leads me to ask if there is some simple definition
> of what reint actually means other than 'reintegrated operations'? 

I'd bet on "request identification" or something along those lines.

> Perhaps such a definition will help explain why setattr is a reint
> counter but getattr is not.  In fact, I have seen getattr_lock change
> a lot more than getattr.  What is the difference between the 2
> (obviously the latter is some sort of lock but it must be used more
> than just when incrementing getattr since they don't change
> together)?

I'm only speculating here, but I believe that extended attributes which 
are modifiable by a user on a client (like ACLs) are counted in 
*_xattr, while internal extended attributes used by the MDS, are 
counted in gettatr.

> That all said, it feels like the data to report is all the reints,
> getattr, getattr_lock and sync.  

I would also be interested in seeing (dis)connect (this can probably 
reveal network problems, if it increases too much), as well as quotactl 
and get/setxattr, since I use quotas and ACLs. :)


Cheers,
-- 
Kilian