Re: [RFC 0/6] Backing Store for sysfs

Christian Borntraeger
2003-10-06T12:35:12Z

> Hi,
>
> The following patch set(mailed separately) provides a prototype for a
backing
> store mechanism for sysfs. Currently sysfs pins all its dentries and
inodes in
> memory there by wasting kernel lowmem even when it is not mounted.
>
> With this patch set we create sysfs dentry whenever it is required like
> other real filesystems and, age and free it as per the dcache rules. We
> now save significant amount of Lowmem by avoiding un-necessary pinning.

A more mature patch could be a possible solution of some problems we faced
with sysfs.
I have s390 test system with ~ 20000 devices. Memory consumption _without_
this
patch is horribly high.
Slab uses 346028 kB of memory, most of it is dentry and inode cache.
I tried the patch, its boots, memory usage is much better, but it is
somewhat
broken with our ccw devices as I cannot bring up our ccwgroup network
devices.
Therefore I dont have reliable memory results.
Almost nobody would use 20000 devices on a S390, but with some shared
OSA-card
100 or 200 devices is realistic. Even in this case, memory consumption is
much higher
than with 2.4.

I still have to look closer on this patch, if there are some deeper
problems.
Until I find something, I think this patch could be really helpful for
computers with lots of devices.

--
Mit freundlichen Grüßen / Best Regards

Christian Bornträger
IBM Deutschland Entwicklung GmbH
eServer SW System Evaluation + Test
email: CBORNTRA@de.ibm.com
Tel +49 7031 16 1975