Re: [PATCH] memcg: fix typo in the soft_limit stats.

On Wed, 18 May 2011 08:49:19 +0900
KAMEZAWA Hiroyuki [off-list ref] wrote:

On Mon, 16 May 2011 17:18:20 -0700
Andrew Morton [off-list ref] wrote:

quoted

On Mon, 16 May 2011 17:05:02 -0700
Ying Han [off-list ref] wrote:

quoted

On Mon, May 16, 2011 at 4:15 PM, Johannes Weiner [off-list ref] wrote:

quoted

On Mon, May 16, 2011 at 03:00:30PM -0700, Ying Han wrote:

quoted

This fixes the typo in the memory.stat including the following two
stats:

$ cat /dev/cgroup/memory/A/memory.stat
total_soft_steal 0
total_soft_scan 0

And change it to:

$ cat /dev/cgroup/memory/A/memory.stat
total_soft_kswapd_steal 0
total_soft_kswapd_scan 0

Signed-off-by: Ying Han <redacted>

I am currently proposing and working on a scheme that makes the soft
limit not only a factor for global memory pressure, but for
hierarchical reclaim in general, to prefer child memcgs during reclaim
that are in excess of their soft limit.

Because this means prioritizing memcgs over one another, rather than
having explicit soft limit reclaim runs, there is no natural counter
for pages reclaimed due to the soft limit anymore.

Thus, for the patch that introduces this counter:

Nacked-by: Johannes Weiner [off-list ref]

This patch is fixing a typo of the stats being integrated into mmotm. Does
it make sense to fix the
existing stats first while we are discussing other approaches?

It would be quite bad to add new userspace-visible stats and to then
take them away again.

yes.

quoted

But given that memcg-add-stats-to-monitor-soft_limit-reclaim.patch is
queued for 2.6.39-rc1, we could proceed with that plan and then make
sure that Johannes's changes are merged either prior to 2.6.40 or
they are never merged at all.

Or we could just leave out the stats until we're sure.  Not having them
for a while is not as bad as adding them and then removing them.

I agree. I'm okay with removing them for a while. Johannes and Ying, could you
make a concensus ? IMHO, Johannes' work for making soft-limit co-operative with
hirerachical reclaim makes sense and agree to leave counter name as it is.

After reading threads, an another idea comes. Johannes' soft_limit just works
when the hierarchy hit limit. I think pages are not reclaimed by soft_limit...
it just reclaimed by the limit because of hierarchy. Right ?

Hmm, I'm not sure using counter of softlimit or (new) counter of reclaimed-by-parent
for that purpose.

But I think this change of stat name is not necessary, anyway.

Thanks,
-Kame



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