[lustre-devel] have df report a more up-to-date view of the filesystem

quentin.bouget at cea.fr quentin.bouget at cea.fr
Tue May 23 06:34:04 PDT 2017

Le 19/05/2017 à 04:14, Dilger, Andreas a écrit :
> On May 17, 2017, at 13:16, quentin.bouget at cea.fr wrote:
>> Hi everyone,
>> In LU-8940 I describe an issue I am having with df in Lustre's tests. In short, df/statfs can report outdated information about a Lustre filesystem; given enough time, its output gets correct. From what I understand, statfs cannot report an "always up-to-date" view of the filesystem as this would cost too much time and resources.
>> I would like to know what you guys think of having Lustre's statfs operation report a view of the filesystem at least as new as when the last sync operation completed?
>> My point being that users (and tests) would be able to run df --sync to get up-to-date information (at the cost of a sync operation, and maybe some accounting for statfs).
> This isn't really a problem with "df".  The client will cache the statfs information for at most 1s until it refreshes it again.
> What it appears is happening (from LU-8940) is that unlinking a bunch of files doesn't delete the files and destroy the objects fast enough for the small test filesystem.  If there is a real system being used then it would likely not have any significant problems seen on these small filesystems.
> There are methods in test-framework.sh (e.g. wait_delete_completed()) to handle the free space reporting when the filesystem is full.
> Cheers, Andreas
> --
> Andreas Dilger
> Lustre Principal Architect
> Intel Corporation

It would seem wait_delete_completed() is exactly what we were looking 
for to solve LU-8940.

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