Re: [PATCH -mmotm 0/5] memcg: per cgroup dirty limit (v7)

[Vivek Goyal <vgoyal@redhat.com>]

On Thu, Mar 18, 2010 at 12:23:27AM +0530, Balbir Singh wrote:
> * Vivek Goyal <vgoyal@redhat.com> [2010-03-17 09:34:07]:
> 
> > > > 
> > > > root cgroup
> > > > ==========
> > > > #time dd if=/dev/zero of=/root/zerofile bs=4K count=1M
> > > > 4294967296 bytes (4.3 GB) copied, 56.098 s, 76.6 MB/s
> > > > 
> > > > real	0m56.614s
> > > > 
> > > > test1 cgroup with memory limit 100M
> > > > ===================================
> > > > # time dd if=/dev/zero of=/root/zerofile1 bs=4K count=1M
> > > > 4294967296 bytes (4.3 GB) copied, 19.8097 s, 217 MB/s
> > > > 
> > > > real	0m19.992s
> > > > 
> > > 
> > > This is strange, did you flish the cache between the two runs?
> > > NOTE: Since the files are same, we reuse page cache from the
> > > other cgroup.
> > 
> > Files are different. Note suffix "1".
> >
> 
> Thanks, I'll get the perf output and see what I get. 

One more thing I noticed and that is, it happens only if we limit the
memory of cgroup to 100M. If same cgroup test1 is unlimited memory 
thing, then it did not happen.

I also did not notice this happening on other system where I have 4G of
memory. So it also seems to be related with only bigger configurations.

Thanks
Vivek

> 
> -- 
> 	Three Cheers,
> 	Balbir