Re: Recursive chmod/chown OOM kills box with 32MB RAM

[Chris Mason <mason@suse.com>]

On Monday 30 January 2006 01:11, Hans Reiser wrote:
> Chris, would Denis Vlasenko wrote:
> >[CCing namesys]
> >
> >Narrowed it down to 100% reproducible case:
> >
> >	chown -Rc 0:<n> .
> >
> >in a top directory of tree containing ~21938 files
> >on reiser3 partition:
> >
> >	/dev/sdc3 on /.3 type reiserfs (rw,noatime)
> >
> >causes oom kill storm. "ls -lR", "find ." etc work fine.
> >
> >I suspected that it is a leak in winbindd libnss module,
> >but chown does not seem to grow larger in top, and also
> >running it under softlimit -m 400000 still causes oom kills
> >while chown's RSS stays below 4MB.

In order for the journaled filesystems to make sure the FS is consistent after 
a crash, we need to keep some blocks in memory until other blocks have been 
written.  These blocks are pinned, and can't be freed until a certain amount 
of io is done.

In the case of reiserfs, it might pin as much as the size of the journal at 
any time.  The default journal is 32MB, which is much too large for a system 
with only 32MB of ram.

You can shrink the log of an existing filesystem.  The minimum size is 513 
blocks, you might try 1024 as a good starting poing.

reiserfstune -s 1024 /dev/xxxx

The filesystem must be unmounted first.

-chris