Re: [PATCH 1/7] memcg: add high/low watermark to res_counter

[Michal Hocko <mhocko@suse.cz>]

On Wed 04-05-11 10:16:39, Ying Han wrote:
> On Wed, May 4, 2011 at 1:58 AM, Michal Hocko <mhocko@suse.cz> wrote:
> > On Tue 03-05-11 10:01:27, Ying Han wrote:
> >> On Tue, May 3, 2011 at 1:25 AM, Michal Hocko <mhocko@suse.cz> wrote:
> >> > On Tue 03-05-11 16:45:23, KOSAKI Motohiro wrote:
> >> >> 2011/5/3 Michal Hocko <mhocko@suse.cz>:
> >> >> > On Sun 01-05-11 15:06:02, KOSAKI Motohiro wrote:
> >> >> >> > On Mon 25-04-11 18:28:49, KAMEZAWA Hiroyuki wrote:
> > [...]
> >> >> >> Can you please clarify this? I feel it is not opposite semantics.
> >> >> >
> >> >> > In the global reclaim low watermark represents the point when we _start_
> >> >> > background reclaim while high watermark is the _stopper_. Watermarks are
> >> >> > based on the free memory while this proposal makes it based on the used
> >> >> > memory.
> >> >> > I understand that the result is same in the end but it is really
> >> >> > confusing because you have to switch your mindset from free to used and
> >> >> > from under the limit to above the limit.
> >> >>
> >> >> Ah, right. So, do you have an alternative idea?
> >> >
> >> > Why cannot we just keep the global reclaim semantic and make it free
> >> > memory (hard_limit - usage_in_bytes) based with low limit as the trigger
> >> > for reclaiming?
> >>
> > [...]
> >> The current scheme
> >
> > What is the current scheme?
> 
> using the "usage_in_bytes" instead of "free"
> 
> >> is closer to the global bg reclaim which the low is triggering reclaim
> >> and high is stopping reclaim. And we can only use the "usage" to keep
> >> the same API.

And how is this closer to the global reclaim semantic which is based on
the available memory?
What I am trying to say here is that this new watermark concept doesn't
fit in with the global reclaim. Well, standard user might not be aware
of the zone watermarks at all because they cannot be set. But still if
you are analyzing your memory usage you still check and compare free
memory to min/low/high watermarks to find out what is the current memory
pressure.
If we had another concept with cgroups you would need to switch your 
mindset to analyze things.

I am sorry, but I still do not see any reason why those cgroup watermaks
cannot be based on total-usage.
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>