[Lustre-discuss] collectl
Mark Seger
Mark.Seger at hp.com
Wed Jul 30 11:52:19 PDT 2008
I just did an interesting experiment. If I run the command 'lfs df' in
a tight loop, the reint_statfs counters increments once but if I stick
in a sleep 1, it increments it for every call. is this a bug or a
feature? Is it doing some kind of short-lived cache lookup in the first
can but not the second?
-mark
Kilian CAVALOTTI wrote:
> 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,
>
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