Messages in this thread | | | Date | Wed, 24 Sep 2008 16:11:40 +0900 | From | KAMEZAWA Hiroyuki <> | Subject | Re: [PATCH 3.6/13] memcg: add function to move account. |
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On Wed, 24 Sep 2008 15:50:11 +0900 Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> wrote:
> On Mon, 22 Sep 2008 20:09:48 +0900, KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> wrote: > > Sorry, this patchs is after "3.5" , before "4".... > > > > == > > This patch provides a function to move account information of a page between > > mem_cgroups. > > > > This moving of page_cgroup is done under > > - the page is locked. > > - lru_lock of source/destination mem_cgroup is held. > > > > Then, a routine which touches pc->mem_cgroup without page_lock() should > > confirm pc->mem_cgroup is still valid or not. Typlical code can be following. > > > > (while page is not under lock_page()) > > mem = pc->mem_cgroup; > > mz = page_cgroup_zoneinfo(pc) > > spin_lock_irqsave(&mz->lru_lock); > > if (pc->mem_cgroup == mem) > > ...../* some list handling */ > > spin_unlock_irq(&mz->lru_lock); > > > > Is this check needed? > Both move_lists and move_account takes page_cgroup lock. > __mem_cgroup_move_lists() doesn't take. But yes, if you know what it does, you can reduce checks. Above is example.
Thanks, -Kame
> > Thanks, > Daisuke Nishimura. > > > If you find page_cgroup from mem_cgroup's LRU under mz->lru_lock, you don't > > have to worry about anything. > > > > Changelog: (v3) -> (v4) > > - no changes. > > Changelog: (v2) -> (v3) > > - added lock_page_cgroup(). > > - splitted out from new-force-empty patch. > > - added how-to-use text. > > - fixed race in __mem_cgroup_uncharge_common(). > > > > Signed-off-by: KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> > > > > mm/memcontrol.c | 85 ++++++++++++++++++++++++++++++++++++++++++++++++++++++-- > > 1 file changed, 82 insertions(+), 3 deletions(-) > > > > Index: mmotm-2.6.27-rc6+/mm/memcontrol.c > > =================================================================== > > --- mmotm-2.6.27-rc6+.orig/mm/memcontrol.c > > +++ mmotm-2.6.27-rc6+/mm/memcontrol.c > > @@ -424,6 +424,7 @@ int task_in_mem_cgroup(struct task_struc > > void mem_cgroup_move_lists(struct page *page, enum lru_list lru) > > { > > struct page_cgroup *pc; > > + struct mem_cgroup *mem; > > struct mem_cgroup_per_zone *mz; > > unsigned long flags; > > > > @@ -442,9 +443,14 @@ void mem_cgroup_move_lists(struct page * > > > > pc = page_get_page_cgroup(page); > > if (pc) { > > + mem = pc->mem_cgroup; > > mz = page_cgroup_zoneinfo(pc); > > spin_lock_irqsave(&mz->lru_lock, flags); > > - __mem_cgroup_move_lists(pc, lru); > > + /* > > + * check against the race with move_account. > > + */ > > + if (likely(mem == pc->mem_cgroup)) > > + __mem_cgroup_move_lists(pc, lru); > > spin_unlock_irqrestore(&mz->lru_lock, flags); > > } > > unlock_page_cgroup(page); > > @@ -565,6 +571,71 @@ unsigned long mem_cgroup_isolate_pages(u > > return nr_taken; > > } > > > > +/** > > + * mem_cgroup_move_account - move account of the page > > + * @page ... the target page of being moved. > > + * @pc ... page_cgroup of the page. > > + * @from ... mem_cgroup which the page is moved from. > > + * @to ... mem_cgroup which the page is moved to. > > + * > > + * The caller must confirm following. > > + * 1. lock the page by lock_page(). > > + * 2. disable irq. > > + * 3. lru_lock of old mem_cgroup should be held. > > + * 4. pc is guaranteed to be valid and on mem_cgroup's LRU. > > + * > > + * Because we cannot call try_to_free_page() here, the caller must guarantee > > + * this moving of change never fails. Currently this is called only against > > + * root cgroup, which has no limitation of resource. > > + * Returns 0 at success, returns 1 at failure. > > + */ > > +int mem_cgroup_move_account(struct page *page, struct page_cgroup *pc, > > + struct mem_cgroup *from, struct mem_cgroup *to) > > +{ > > + struct mem_cgroup_per_zone *from_mz, *to_mz; > > + int nid, zid; > > + int ret = 1; > > + > > + VM_BUG_ON(!irqs_disabled()); > > + VM_BUG_ON(!PageLocked(page)); > > + > > + nid = page_to_nid(page); > > + zid = page_zonenum(page); > > + from_mz = mem_cgroup_zoneinfo(from, nid, zid); > > + to_mz = mem_cgroup_zoneinfo(to, nid, zid); > > + > > + if (res_counter_charge(&to->res, PAGE_SIZE)) { > > + /* Now, we assume no_limit...no failure here. */ > > + return ret; > > + } > > + if (!try_lock_page_cgroup(page)) { > > + res_counter_uncharge(&to->res, PAGE_SIZE); > > + return ret; > > + } > > + > > + if (page_get_page_cgroup(page) != pc) { > > + res_counter_uncharge(&to->res, PAGE_SIZE); > > + goto out; > > + } > > + > > + if (spin_trylock(&to_mz->lru_lock)) { > > + __mem_cgroup_remove_list(from_mz, pc); > > + css_put(&from->css); > > + res_counter_uncharge(&from->res, PAGE_SIZE); > > + pc->mem_cgroup = to; > > + css_get(&to->css); > > + __mem_cgroup_add_list(to_mz, pc); > > + ret = 0; > > + spin_unlock(&to_mz->lru_lock); > > + } else { > > + res_counter_uncharge(&to->res, PAGE_SIZE); > > + } > > +out: > > + unlock_page_cgroup(page); > > + > > + return ret; > > +} > > + > > /* > > * Charge the memory controller for page usage. > > * Return > > @@ -752,16 +823,24 @@ __mem_cgroup_uncharge_common(struct page > > if ((ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED) > > && ((PageCgroupCache(pc) || page_mapped(page)))) > > goto unlock; > > - > > +retry: > > + mem = pc->mem_cgroup; > > mz = page_cgroup_zoneinfo(pc); > > spin_lock_irqsave(&mz->lru_lock, flags); > > + if (ctype == MEM_CGROUP_CHARGE_TYPE_MAPPED && > > + unlikely(mem != pc->mem_cgroup)) { > > + /* MAPPED account can be done without lock_page(). > > + Check race with mem_cgroup_move_account() */ > > + spin_unlock_irqrestore(&mz->lru_lock, flags); > > + goto retry; > > + } > > __mem_cgroup_remove_list(mz, pc); > > spin_unlock_irqrestore(&mz->lru_lock, flags); > > > > page_assign_page_cgroup(page, NULL); > > unlock_page_cgroup(page); > > > > - mem = pc->mem_cgroup; > > + > > res_counter_uncharge(&mem->res, PAGE_SIZE); > > css_put(&mem->css); > > > > >
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