On Mon, May 9, 2011 at 4:49 PM, KAMEZAWA Hiroyuki
[off-list ref] wrote:

On Mon, 9 May 2011 14:49:17 +0200
Michal Hocko [off-list ref] wrote:

quoted

On Mon 09-05-11 12:18:17, Johannes Weiner wrote:

quoted

On Mon, May 09, 2011 at 04:10:47PM +0900, KAMEZAWA Hiroyuki wrote:

[...]

quoted

What I am wondering, though: we already have a limit to push back
memcgs when we need memory, the soft limit.  The 'need for memory' is
currently defined as global memory pressure, which we know may be too
late.  The problem is not having no limit, the problem is that we want
to control the time of when this limit is enforced.  So instead of
adding another limit, could we instead add a knob like

    memory.force_async_soft_reclaim

that asynchroneously pushes back to the soft limit instead of having
another, separate limit to configure?

Hmm, ok to me.

I don't have problem of the actual tunable for this, but I don't think
setting the soft_limit as the target for per-memcg background reclaim
is feasible in some cases. That will be too aggressive than it is necessary.

quoted

Sound much better than a separate watermark to me. I am just wondering
how we would implement soft unlimited groups with background reclaim.
Btw. is anybody relying on such configuration? To me it sounds like
something should be either limited or unlimited and making it half of
both is hacky.

I don't think of soft-unlimited configuration. I don't want to handle it
in some automatic way.

Anyway, I'll add
 - _automatic_ background reclaim against the limit of memory, which works
   regarless of softlimit.

I agree to have the background reclaim first w/ automatic watermark
setting and then adding a configurable knob on top of that. So I
assume we keep the same concept of high/low_wmarks, and what's the
suggested default value for the watermarks? The default value now is
equal to hard_limit which disables he per-memcg background reclaim.
Under the new scheme which we remove the configurable tunable, we need
to set it internally based on the hard_limit.

--Ying

 - An interface for force softlimit.

Thanks,
-Kame

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