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Date: Sat, 16 May 2009 02:45:03 +0900 (JST)
From: "KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>
To: balbir@...ux.vnet.ibm.com
Cc: "linux-mm@...ck.org" <linux-mm@...ck.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
"Andrew Morton" <akpm@...ux-foundation.org>,
"KAMEZAWA Hiroyuki" <kamezawa.hiroyu@...fujitsu.com>,
"nishimura@....nes.nec.co.jp" <nishimura@....nes.nec.co.jp>,
"lizf@...fujitsu.com" <lizf@...fujitsu.com>,
"menage@...gle.com" <menage@...gle.com>,
"KOSAKI Motohiro" <m-kosaki@...es.dti.ne.jp>
Subject: Re: [RFC] Low overhead patches for the memory cgroup controller
(v2)
Balbir Singh wrote:
> Feature: Remove the overhead associated with the root cgroup
>
> From: Balbir Singh <balbir@...ux.vnet.ibm.com>
>
> This patch changes the memory cgroup and removes the overhead associated
> with LRU maintenance of all pages in the root cgroup. As a side-effect, we
> can
> no longer set a memory hard limit in the root cgroup.
>
> A new flag is used to track page_cgroup associated with the root cgroup
> pages. A new flag to track whether the page has been accounted or not
> has been added as well.
>
> Review comments higly appreciated
>
> Tests
>
> 1. Tested with allocate, touch and limit test case for a non-root cgroup
> 2. For the root cgroup tested performance impact with reaim
>
>
> +patch mmtom-08-may-2009
> AIM9 1362.93 1338.17
> Dbase 17457.75 16021.58
> New Dbase 18070.18 16518.54
> Shared 9681.85 8882.11
> Compute 16197.79 15226.13
>
Hmm, at first impression, I can't convice the numbers...
Just avoiding list_add/del makes programs _10%_ faster ?
Could you show changes in cpu cache-miss late if you can ?
(And why Aim9 goes bad ?)
Hmm, page_cgroup_zoneinfo() is accessed anyway, then...per zone counter
is not a problem here..
Could you show your .config and environment ?
When I trunst above numbers, it seems there is more optimization/
prefetch point in usual path
BTW, how the perfomance changes in children(not default) groups ?
> 3. Tested accounting in root cgroup to make sure it looks sane and
> correct.
>
Not sure but swap and shmem case should be checked carefully..
> Signed-off-by: Balbir Singh <balbir@...ux.vnet.ibm.com>
> ---
>
> include/linux/page_cgroup.h | 10 ++++++++++
> mm/memcontrol.c | 29 ++++++++++++++++++++++++++---
> mm/page_cgroup.c | 1 -
> 3 files changed, 36 insertions(+), 4 deletions(-)
>
>
> diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h
> index 7339c7b..8b85752 100644
> --- a/include/linux/page_cgroup.h
> +++ b/include/linux/page_cgroup.h
> @@ -26,6 +26,8 @@ enum {
> PCG_LOCK, /* page cgroup is locked */
> PCG_CACHE, /* charged as cache */
> PCG_USED, /* this object is in use. */
> + PCG_ROOT, /* page belongs to root cgroup */
> + PCG_ACCT, /* page has been accounted for */
Reading codes, this PCG_ACCT should be PCG_AcctLRU.
> };
>
> #define TESTPCGFLAG(uname, lname) \
> @@ -46,6 +48,14 @@ TESTPCGFLAG(Cache, CACHE)
> TESTPCGFLAG(Used, USED)
> CLEARPCGFLAG(Used, USED)
>
> +SETPCGFLAG(Root, ROOT)
> +CLEARPCGFLAG(Root, ROOT)
> +TESTPCGFLAG(Root, ROOT)
> +
> +SETPCGFLAG(Acct, ACCT)
> +CLEARPCGFLAG(Acct, ACCT)
> +TESTPCGFLAG(Acct, ACCT)
> +
> static inline int page_cgroup_nid(struct page_cgroup *pc)
> {
> return page_to_nid(pc->page);
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index 9712ef7..18d2819 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -43,6 +43,7 @@
>
> struct cgroup_subsys mem_cgroup_subsys __read_mostly;
> #define MEM_CGROUP_RECLAIM_RETRIES 5
> +struct mem_cgroup *root_mem_cgroup __read_mostly;
>
> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_SWAP
> /* Turned on only when memory cgroup is enabled && really_do_swap_account
> = 0 */
> @@ -196,6 +197,10 @@ enum charge_type {
> #define PCGF_CACHE (1UL << PCG_CACHE)
> #define PCGF_USED (1UL << PCG_USED)
> #define PCGF_LOCK (1UL << PCG_LOCK)
> +/* Not used, but added here for completeness */
> +#define PCGF_ROOT (1UL << PCG_ROOT)
> +#define PCGF_ACCT (1UL << PCG_ACCT)
> +
> static const unsigned long
> pcg_default_flags[NR_CHARGE_TYPE] = {
> PCGF_CACHE | PCGF_USED | PCGF_LOCK, /* File Cache */
> @@ -420,7 +425,7 @@ void mem_cgroup_del_lru_list(struct page *page, enum
> lru_list lru)
> return;
> pc = lookup_page_cgroup(page);
> /* can happen while we handle swapcache. */
> - if (list_empty(&pc->lru) || !pc->mem_cgroup)
> + if ((!PageCgroupAcct(pc) && list_empty(&pc->lru)) || !pc->mem_cgroup)
> return;
> /*
> * We don't check PCG_USED bit. It's cleared when the "page" is finally
> @@ -429,6 +434,9 @@ void mem_cgroup_del_lru_list(struct page *page, enum
> lru_list lru)
> mz = page_cgroup_zoneinfo(pc);
> mem = pc->mem_cgroup;
> MEM_CGROUP_ZSTAT(mz, lru) -= 1;
> + ClearPageCgroupAcct(pc);
> + if (PageCgroupRoot(pc))
> + return;
> list_del_init(&pc->lru);
> return;
> }
> @@ -452,8 +460,8 @@ void mem_cgroup_rotate_lru_list(struct page *page,
> enum lru_list lru)
> * For making pc->mem_cgroup visible, insert smp_rmb() here.
> */
> smp_rmb();
> - /* unused page is not rotated. */
> - if (!PageCgroupUsed(pc))
> + /* unused or root page is not rotated. */
> + if (!PageCgroupUsed(pc) || PageCgroupRoot(pc))
> return;
> mz = page_cgroup_zoneinfo(pc);
> list_move(&pc->lru, &mz->lists[lru]);
> @@ -477,6 +485,9 @@ void mem_cgroup_add_lru_list(struct page *page, enum
> lru_list lru)
>
> mz = page_cgroup_zoneinfo(pc);
> MEM_CGROUP_ZSTAT(mz, lru) += 1;
> + SetPageCgroupAcct(pc);
> + if (PageCgroupRoot(pc))
> + return;
> list_add(&pc->lru, &mz->lists[lru]);
> }
I think set/clear flag here adds race condtion....because pc->flags is
modfied by
pc->flags = pcg_dafault_flags[ctype] in commit_charge()
you have to modify above lines to be
SetPageCgroupCache(pc) or some..
...
SetPageCgroupUsed(pc)
Then, you can use set_bit() without lock_page_cgroup().
(Currently, pc->flags is modified only under lock_page_cgroup(), so,
non atomic code is used.)
Regards,
-Kame
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