[Gluster-users] Old story - glusterfs memory usage

Krzysztof Strasburger strasbur at chkw386.ch.pwr.wroc.pl
Thu Mar 25 10:38:00 UTC 2010

I upgraded today from 2.0.8 to 3.0.3.
The first sad impression was that unify no longer works, but it is not that
important. Not a surprise. Switched to dht. Tried my old "du" test:
du /home
(/home is a glusterfs filesystem, of course ;) and saw again the bad old
unlimited increase of glusterfs clients memory usage. I hoped that the
problem went to quick-read, but it didn't.
So switched back to 2.0.10rc1, to restore unify.
And then did a simple test, to be sure that no translators are to be blamed.
I created the following, trivial setup:

file loopback.vol:
volume loopback
 type storage/posix
 option directory /root/loopback

And then mounted /root/loopback on /root/loop-test:

mount -t glusterfs loopback.vol /root/loop-test

Do you see? No translators, even no server and networking. Just a loopback
to a directory on the local machine.

I copied then the /usr directory to /root/loop-test (c.a. 160000 files).
And then ran "du /root/loop-test".
Memory usage of respective glusterfs process went up from 16 MB to 50 MB.
I could reproduce it perfectly by umounting /root/loop-test, mounting it
again and re-running "du".
More files touched mean more memory used by glusterfs.
This is not a memory leak. Repeating this "du" does not cause memory
usage go even a single byte up. Glusterfs client keeps somewhere an 
information about _every file touched_, and keeps it _forever_. As the situation 
did not improve since the times of glusterfs 1.3, I assume this behavior 
to be a part of its design. IMHO a wrong one. This is not a feature,
this is a bug. It costs memory and probably performace too, if it is a kind
of cache (with millions of entries, potentially).
I filed a bug report almost one year ago - no change. Dear other users of
glusterfs - are you at least able to reproduce this memory consumption
problem? If it occurs on my site only, then the reason is somewhere in my
system setup, otherwise - let us do something about it, finally.
It is not in translators, it is in the core of glusterfs.
With regards
Krzysztof Strasburger

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