Re: [PATCH 2/2] Add stats to monitor soft_limit reclaim

[Balbir Singh <balbir@linux.vnet.ibm.com>]

* Ying Han <yinghan@google.com> [2011-04-28 20:28:54]:

> On Thu, Apr 28, 2011 at 4:51 PM, Hiroyuki Kamezawa
> <kamezawa.hiroyuki@gmail.com> wrote:
> > 2011/4/29 Ying Han <yinghan@google.com>:
> >> On Thu, Apr 28, 2011 at 3:37 PM, Ying Han <yinghan@google.com> wrote:
> >>> This patch extend the soft_limit reclaim stats to both global background
> >>> reclaim and global direct reclaim.
> >>>
> >>> We have a thread discussing the naming of some of the stats. Both
> >>> KAMEZAWA and Johannes posted the proposals. The following stats are based
> >>> on what i had before that thread. I will make the corresponding change on
> >>> the next post when we make decision.
> >>>
> >>> $cat /dev/cgroup/memory/A/memory.stat
> >>> kswapd_soft_steal 1053626
> >>> kswapd_soft_scan 1053693
> >>> direct_soft_steal 1481810
> >>> direct_soft_scan 1481996
> >>>
> >>> Signed-off-by: Ying Han <yinghan@google.com>
> >>> ---
> >>>  Documentation/cgroups/memory.txt |   10 ++++-
> >>>  mm/memcontrol.c                  |   68 ++++++++++++++++++++++++++++----------
> >>>  2 files changed, 58 insertions(+), 20 deletions(-)
> >>>
> >>> diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt
> >>> index 0c40dab..fedc107 100644
> >>> --- a/Documentation/cgroups/memory.txt
> >>> +++ b/Documentation/cgroups/memory.txt
> >>> @@ -387,8 +387,14 @@ pgpgout            - # of pages paged out (equivalent to # of uncharging events).
> >>>  swap           - # of bytes of swap usage
> >>>  pgfault                - # of page faults.
> >>>  pgmajfault     - # of major page faults.
> >>> -soft_steal     - # of pages reclaimed from global hierarchical reclaim
> >>> -soft_scan      - # of pages scanned from global hierarchical reclaim
> >>> +soft_kswapd_steal- # of pages reclaimed in global hierarchical reclaim from
> >>> +               background reclaim
> >>> +soft_kswapd_scan - # of pages scanned in global hierarchical reclaim from
> >>> +               background reclaim
> >>> +soft_direct_steal- # of pages reclaimed in global hierarchical reclaim from
> >>> +               direct reclaim
> >>> +soft_direct_scan- # of pages scanned in global hierarchical reclaim from
> >>> +               direct reclaim
> >
> > Thank you for CC.
> >
> > I don't have strong opinion but once we add interfaces to mainline,
> > it's hard to rename them. So, it's better to make a list of what name
> > we'll need in future.
> >
> > Now, your naming has a format as [Reason]-[Who reclaim]-[What count?]
> > soft_kswapd_steal
> > soft_kswapd_scan
> > soft_direct_steal
> > soft_direct_scan
> >
> > Ok, we can make a name for wmark and limit reclaim as
> >
> > limit_direct_steal/scan
> > wmark_bg_steal/scan
> >
> > Then, assume we finally do round-robin scan of memcg regardless of softlimit by
> > removing global LRU, what name do we have ? Hmm,
> >
> > kernel_kswapd_scan/steal
> > kernel_direct_scan/steal
> >
> > ?
> 
> Johannes has the proposal to separate out reclaims on the memcg
> internally and externally. And then apply the format
> [Reason]-[Who reclaim]-[What count?], also i added the 4th item .
> 
> 1. when the memcg hits its hard_limit
> > limit_direct_steal
> > limit_direct_scan
> 
> 2. when the memcg hits its wmark
> > wmark_kswapd_steal
> > wmark_kswapd_scan
> 
> 3. the global direct reclaim triggers soft_limit pushback
> > soft_direct_steal
> > soft_direct_scan
> 
> 4. hierarchy-triggered direct reclaim
> > limit_hierarchy_steal
> > limit_hierarchy_scan
> 
> 5. the global bg reclaim triggers soft_limit pushback
> > soft_kswapd_steal
> > soft_kswapd_scan
>

I like these names, but these are more developer friendly than end
user friendly.

-- 
	Three Cheers,
	Balbir

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