Messages in this thread | | | Date | Sat, 16 May 2009 02:45:03 +0900 (JST) | Subject | Re: [RFC] Low overhead patches for the memory cgroup controller (v2) | From | "KAMEZAWA Hiroyuki" <> |
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Balbir Singh wrote: > Feature: Remove the overhead associated with the root cgroup > > From: Balbir Singh <balbir@linux.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@linux.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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