On Tue 20-09-11 10:45:53, Johannes Weiner wrote:

On Mon, Sep 19, 2011 at 02:53:33PM +0200, Michal Hocko wrote:

quoted

Hi,

On Mon 12-09-11 12:57:18, Johannes Weiner wrote:

quoted

Memory control groups are currently bolted onto the side of
traditional memory management in places where better integration would
be preferrable.  To reclaim memory, for example, memory control groups
maintain their own LRU list and reclaim strategy aside from the global
per-zone LRU list reclaim.  But an extra list head for each existing
page frame is expensive and maintaining it requires additional code.

This patchset disables the global per-zone LRU lists on memory cgroup
configurations and converts all its users to operate on the per-memory
cgroup lists instead.  As LRU pages are then exclusively on one list,
this saves two list pointers for each page frame in the system:

page_cgroup array size with 4G physical memory

  vanilla: [    0.000000] allocated 31457280 bytes of page_cgroup
  patched: [    0.000000] allocated 15728640 bytes of page_cgroup

At the same time, system performance for various workloads is
unaffected:

100G sparse file cat, 4G physical memory, 10 runs, to test for code
bloat in the traditional LRU handling and kswapd & direct reclaim
paths, without/with the memory controller configured in

  vanilla: 71.603(0.207) seconds
  patched: 71.640(0.156) seconds

  vanilla: 79.558(0.288) seconds
  patched: 77.233(0.147) seconds

100G sparse file cat in 1G memory cgroup, 10 runs, to test for code
bloat in the traditional memory cgroup LRU handling and reclaim path

  vanilla: 96.844(0.281) seconds
  patched: 94.454(0.311) seconds

4 unlimited memcgs running kbuild -j32 each, 4G physical memory, 500M
swap on SSD, 10 runs, to test for regressions in kswapd & direct
reclaim using per-memcg LRU lists with multiple memcgs and multiple
allocators within each memcg

  vanilla: 717.722(1.440) seconds [ 69720.100(11600.835) majfaults ]
  patched: 714.106(2.313) seconds [ 71109.300(14886.186) majfaults ]

16 unlimited memcgs running kbuild, 1900M hierarchical limit, 500M
swap on SSD, 10 runs, to test for regressions in hierarchical memcg
setups

  vanilla: 2742.058(1.992) seconds [ 26479.600(1736.737) majfaults ]
  patched: 2743.267(1.214) seconds [ 27240.700(1076.063) majfaults ]

I guess you want to have this in the first patch to have it for
reference once it gets to the tree, right? I have no objections but it
seems unrelated to the patch and so it might be confusing a bit. I
haven't seen other patches in the series so there is probably no better
place to put this.

Andrew usually hand-picks what's of long-term interest from the series
description and puts it in the first patch.  I thought I'd save him
the trouble.

Understood

[...]

quoted

quoted

diff --git a/mm/memcontrol.c b/mm/memcontrol.c
index b76011a..912c7c7 100644
--- a/mm/memcontrol.c
+++ b/mm/memcontrol.c

@@ -781,83 +781,75 @@ struct mem_cgroup *try_get_mem_cgroup_from_mm(struct mm_struct *mm)
 	return memcg;
 }
 
-/* The caller has to guarantee "mem" exists before calling this */

Shouldn't we have a similar comment that we have to keep a reference to
root if non-NULL. A mention about remember parameter and what is it used
for (hierarchical reclaim) would be helpful as well.

The only thing that dictates the lifetime of a memcg is its reference
count, so having a reference count while operating on a memecg is not
even a question for all existing memcg-internal callsites.

Fair enough.

But I did, in fact, add kernel-doc style documentation to
mem_cgroup_iter() when it becomes a public interface in 5/11.  Can you
take a look and tell me whether you are okay with that?

OK, I will comment on that patch once I get to it.

[...]

Thanks!
-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic

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