Re: [patch] memcg: fix unit mismatch in memcg oom limitcalculation

[David Rientjes]

On Tue, 9 Nov 2010, Greg Thelen wrote:

> Johannes Weiner <hannes@xxxxxxxxxxx> writes:
> 
> > Adding the number of swap pages to the byte limit of a memory control
> > group makes no sense.  Convert the pages to bytes before adding them.
> >
> > The only user of this code is the OOM killer, and the way it is used
> > means that the error results in a higher OOM badness value.  Since the
> > cgroup limit is the same for all tasks in the cgroup, the error should
> > have no practical impact at the moment.
> >
> > But let's not wait for future or changing users to trip over it.
> 
> Thanks for the fix.
> 
> > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx>
> Reviewed-by: Greg Thelen <gthelen@xxxxxxxxxx>
> 

Nice catch, but it's done in the opposite way: the oom killer doesn't use 
byte limits but page limits.  So this needs to be

	(res_counter_read_u64(&memcg->res, RES_LIMIT) >> PAGE_SHIFT) +
			total_swap_pages;
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