From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail144.messagelabs.com (mail144.messagelabs.com [216.82.254.51]) by kanga.kvack.org (Postfix) with SMTP id 4BA796B0044 for ; Fri, 6 Nov 2009 01:38:07 -0500 (EST) Received: from m3.gw.fujitsu.co.jp ([10.0.50.73]) by fgwmail5.fujitsu.co.jp (Fujitsu Gateway) with ESMTP id nA66c47u020806 for (envelope-from kamezawa.hiroyu@jp.fujitsu.com); Fri, 6 Nov 2009 15:38:04 +0900 Received: from smail (m3 [127.0.0.1]) by outgoing.m3.gw.fujitsu.co.jp (Postfix) with ESMTP id CB61845DE50 for ; Fri, 6 Nov 2009 15:38:03 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (s3.gw.fujitsu.co.jp [10.0.50.93]) by m3.gw.fujitsu.co.jp (Postfix) with ESMTP id A6D7645DE4F for ; Fri, 6 Nov 2009 15:38:03 +0900 (JST) Received: from s3.gw.fujitsu.co.jp (localhost.localdomain [127.0.0.1]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id 52DF61DB803B for ; Fri, 6 Nov 2009 15:38:03 +0900 (JST) Received: from ml14.s.css.fujitsu.com (ml14.s.css.fujitsu.com [10.249.87.104]) by s3.gw.fujitsu.co.jp (Postfix) with ESMTP id F34EC1DB803F for ; Fri, 6 Nov 2009 15:37:59 +0900 (JST) Date: Fri, 6 Nov 2009 15:35:26 +0900 From: KAMEZAWA Hiroyuki Subject: Re: [PATCH -mmotm 6/8] memcg: recharge charges of anonymous page Message-Id: <20091106153526.19b70518.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20091106141448.6548687a.nishimura@mxp.nes.nec.co.jp> References: <20091106141011.3ded1551.nishimura@mxp.nes.nec.co.jp> <20091106141448.6548687a.nishimura@mxp.nes.nec.co.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org To: Daisuke Nishimura Cc: linux-mm , Andrew Morton , Balbir Singh , Li Zefan , Paul Menage List-ID: On Fri, 6 Nov 2009 14:14:48 +0900 Daisuke Nishimura wrote: > This patch is the core part of this recharge-at-task-move feature. > It implements functions to recharge charges of anonymous pages mapped only by > the target task. > > Implementation: > - define struct recharge_struct and a valuable of it(recharge) to remember > the count of pre-charges and other information. > - At can_attach(), parse the page table of the task and count the number of > mapped pages which are charged to the source mem_cgroup, and call > __mem_cgroup_try_charge() repeatedly and count up recharge.precharge. > - At attach(), parse the page table again, find a target page as we did in > can_attach(), and call mem_cgroup_move_account() about the page. > - Cancel all charges if recharge.precharge > 0 on failure or at the end of > task move. > Changelog ? > Signed-off-by: Daisuke Nishimura > --- > Documentation/cgroups/memory.txt | 36 +++++- > mm/memcontrol.c | 275 +++++++++++++++++++++++++++++++++++++- > 2 files changed, 306 insertions(+), 5 deletions(-) > > diff --git a/Documentation/cgroups/memory.txt b/Documentation/cgroups/memory.txt > index b871f25..54281ff 100644 > --- a/Documentation/cgroups/memory.txt > +++ b/Documentation/cgroups/memory.txt > @@ -262,10 +262,12 @@ some of the pages cached in the cgroup (page cache pages). > 4.2 Task migration > > When a task migrates from one cgroup to another, it's charge is not > -carried forward. The pages allocated from the original cgroup still > +carried forward by default. The pages allocated from the original cgroup still > remain charged to it, the charge is dropped when the page is freed or > reclaimed. > > +Note: You can move charges of a task along with task migration. See 8. > + > 4.3 Removing a cgroup > > A cgroup can be removed by rmdir, but as discussed in sections 4.1 and 4.2, a > @@ -414,7 +416,37 @@ NOTE1: Soft limits take effect over a long period of time, since they involve > NOTE2: It is recommended to set the soft limit always below the hard limit, > otherwise the hard limit will take precedence. > > -8. TODO > +8. Recharge at task move > + > +Users can move charges associated with a task along with task move, that is, > +uncharge from the old cgroup and charge to the new cgroup. > + > +8.1 Interface > + > +This feature is disabled by default. It can be enabled(and disabled again) by > +writing to memory.recharge_at_immigrate of the destination cgroup. > + > +If you want to enable it > + > +# echo 1 > memory.recharget_at_immigrate > + > +Note: A value more than 1 will be supported in futer. See 8.2. > + > +And if you want disable it again > + > +# echo 0 > memory.recharget_at_immigrate > + > +8.2 Type of charges which can be recharged > + > +We recharge a charge which meets the following conditions. > + > +a. It must be charged to the old cgroup. > +b. A charge of an anonymous page used by the target task. The page must be used > + only by the target task. > + > +Note: More type of pages(e.g. file cache, shmem,) will be supported in future. > + > +9. TODO > > 1. Add support for accounting huge pages (as a separate controller) > 2. Make per-cgroup scanner reclaim not-shared pages first > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index afa1179..f4b7116 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -21,6 +21,8 @@ > #include > #include > #include > +#include > +#include > #include > #include > #include > @@ -239,6 +241,18 @@ struct mem_cgroup { > }; > > /* > + * A data structure and a valiable for recharging charges at task move. > + * "recharge" and its members are protected by cgroup_lock > + */ > +struct recharge_struct { > + struct mem_cgroup *from; > + struct mem_cgroup *to; > + struct task_struct *target; /* the target task being moved */ > + unsigned long precharge; > +}; > +static struct recharge_struct recharge; > + > +/* > * Maximum loops in mem_cgroup_hierarchical_reclaim(), used for soft > * limit reclaim to prevent infinite loops, if they ever occur. > */ > @@ -1496,7 +1510,7 @@ charged: > * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree. > * if they exceeds softlimit. > */ > - if (mem_cgroup_soft_limit_check(mem)) > + if (page && mem_cgroup_soft_limit_check(mem)) > mem_cgroup_update_tree(mem, page); > done: > return 0; > @@ -3416,10 +3430,170 @@ static int mem_cgroup_populate(struct cgroup_subsys *ss, > } > > /* Handlers for recharge at task move. */ > +/** > + * is_target_pte_for_recharge - check a pte whether it is valid for recharge > + * @vma: the vma the pte to be checked belongs > + * @addr: the address corresponding to the pte to be checked > + * @ptent: the pte to be checked > + * @target: the pointer the target page will be stored(can be NULL) > + * > + * Returns > + * 0(RECHARGE_TARGET_NONE): if the pte is not a target for recharge. > + * 1(RECHARGE_TARGET_PAGE): if the page corresponding to this pte is a target > + * for recharge. if @target is not NULL, the page is stored in target->page > + * with extra refcnt got(Callers should handle it). > + * > + * Called with pte lock held. > + */ > +/* We add a new member later. */ > +union recharge_target { > + struct page *page; > +}; > + > +/* We add a new type later. */ > +enum recharge_target_type { > + RECHARGE_TARGET_NONE, /* not used */ > + RECHARGE_TARGET_PAGE, > +}; > + > +static int is_target_pte_for_recharge(struct vm_area_struct *vma, > + unsigned long addr, pte_t ptent, union recharge_target *target) > +{ > + struct page *page; > + struct page_cgroup *pc; > + int ret = 0; > + > + if (!pte_present(ptent)) > + return 0; > + > + page = vm_normal_page(vma, addr, ptent); > + if (!page || !page_mapped(page)) > + return 0; > + /* TODO: We don't recharge file(including shmem/tmpfs) pages for now. */ > + if (!PageAnon(page)) > + return 0; > + /* > + * TODO: We don't recharge shared(used by multiple processes) pages > + * for now. > + */ > + if (page_mapcount(page) > 1) > + return 0; > + if (!get_page_unless_zero(page)) > + return 0; > + > + pc = lookup_page_cgroup(page); > + lock_page_cgroup(pc); > + if (PageCgroupUsed(pc) && pc->mem_cgroup == recharge.from) { > + ret = RECHARGE_TARGET_PAGE; > + if (target) > + target->page = page; > + } > + unlock_page_cgroup(pc); > + > + if (!ret || !target) > + put_page(page); > + > + return ret; > +} > + > +static int mem_cgroup_recharge_do_precharge(void) > +{ > + int ret = -ENOMEM; > + struct mem_cgroup *mem = recharge.to; > + > + ret = __mem_cgroup_try_charge(NULL, GFP_KERNEL, &mem, false, NULL); > + if (ret || !mem) > + return -ENOMEM; > + > + recharge.precharge++; > + return ret; > +} > + > +static int mem_cgroup_recharge_prepare_pte_range(pmd_t *pmd, > + unsigned long addr, unsigned long end, > + struct mm_walk *walk) > +{ > + int ret = 0; > + unsigned long count = 0; > + struct vm_area_struct *vma = walk->private; > + pte_t *pte; > + spinlock_t *ptl; > + > + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); > + for (; addr != end; pte++, addr += PAGE_SIZE) > + if (is_target_pte_for_recharge(vma, addr, *pte, NULL)) > + count++; > + pte_unmap_unlock(pte - 1, ptl); > + > + while (count-- && !ret) > + ret = mem_cgroup_recharge_do_precharge(); > + > + return ret; > +} > + > +static int mem_cgroup_recharge_prepare(void) > +{ > + int ret = 0; > + struct mm_struct *mm; > + struct vm_area_struct *vma; > + > + mm = get_task_mm(recharge.target); > + if (!mm) > + return 0; > + > + down_read(&mm->mmap_sem); > + for (vma = mm->mmap; vma; vma = vma->vm_next) { > + struct mm_walk mem_cgroup_recharge_prepare_walk = { > + .pmd_entry = mem_cgroup_recharge_prepare_pte_range, > + .mm = mm, > + .private = vma, > + }; > + if (signal_pending(current)) { > + ret = -EINTR; > + break; > + } > + if (is_vm_hugetlb_page(vma)) > + continue; > + ret = walk_page_range(vma->vm_start, vma->vm_end, > + &mem_cgroup_recharge_prepare_walk); > + if (ret) > + break; > + cond_resched(); > + } > + up_read(&mm->mmap_sem); > + > + mmput(mm); > + return ret; > +} > + > +static void mem_cgroup_clear_recharge(void) > +{ > + while (recharge.precharge--) > + mem_cgroup_cancel_charge(recharge.to); > + recharge.from = NULL; > + recharge.to = NULL; > + recharge.target = NULL; > +} > + > static int mem_cgroup_can_recharge(struct mem_cgroup *mem, > struct task_struct *p) > { > - return 0; > + int ret; > + struct mem_cgroup *from = mem_cgroup_from_task(p); > + > + if (from == mem) > + return 0; > + > + recharge.from = from; > + recharge.to = mem; > + recharge.target = p; > + recharge.precharge = 0; > + > + ret = mem_cgroup_recharge_prepare(); > + > + if (ret) > + mem_cgroup_clear_recharge(); > + return ret; > } > Hmm...Hmm...looks nicer. But can I have another suggestion ? == static int mem_cgroup_can_recharge(struct mem_cgroup *mem, struct task_struct *p) { unsigned long rss; struct mm_struct *mm; mm = get_task_mm(p); if (!mm) return; rss = get_mm_counter(mm, anon_rss); precharge(rss); mmput(mm); } == Do you think anonymous memory are so shared at "move" as that we need page table scan ? If typical sequence is == fork() -> exec() move child == No problem will happen. > static int mem_cgroup_can_attach(struct cgroup_subsys *ss, > @@ -3442,11 +3616,104 @@ static void mem_cgroup_cancel_attach(struct cgroup_subsys *ss, > struct task_struct *p, > bool threadgroup) > { > + struct mem_cgroup *mem = mem_cgroup_from_cont(cgroup); > + > mutex_unlock(&memcg_tasklist); > + if (mem->recharge_at_immigrate && thread_group_leader(p)) > + mem_cgroup_clear_recharge(); > +} > + > +static int mem_cgroup_recharge_pte_range(pmd_t *pmd, > + unsigned long addr, unsigned long end, > + struct mm_walk *walk) > +{ > + int ret = 0; > + struct vm_area_struct *vma = walk->private; > + pte_t *pte; > + spinlock_t *ptl; > + > +retry: > + pte = pte_offset_map_lock(vma->vm_mm, pmd, addr, &ptl); > + for (; addr != end; addr += PAGE_SIZE) { > + pte_t ptent = *(pte++); > + union recharge_target target; > + int type; > + struct page *page; > + struct page_cgroup *pc; > + > + if (!recharge.precharge) > + break; > + > + type = is_target_pte_for_recharge(vma, addr, ptent, &target); > + switch (type) { > + case RECHARGE_TARGET_PAGE: > + page = target.page; > + if (isolate_lru_page(page)) > + goto put; > + pc = lookup_page_cgroup(page); > + if (!mem_cgroup_move_account(pc, > + recharge.from, recharge.to)) { > + css_put(&recharge.to->css); > + recharge.precharge--; > + } > + putback_lru_page(page); > +put: /* is_target_pte_for_recharge() gets the page */ > + put_page(page); > + break; > + default: > + continue; continue for what ? And we forget "failed to move" pte. This "move" is best-effort service. Right ? > + } > + } > + pte_unmap_unlock(pte - 1, ptl); > + > + if (addr != end) { > + /* > + * We have consumed all precharges we got in can_attach(). > + * We try precharge one by one, but don't do any additional > + * precharges nor recharges to recharge.to if we have failed in > + * precharge once in attach() phase. > + */ > + ret = mem_cgroup_recharge_do_precharge(); > + if (!ret) > + goto retry; > + } > + > + return ret; > } > > static void mem_cgroup_recharge(void) > { > + struct mm_struct *mm; > + struct vm_area_struct *vma; > + > + mm = get_task_mm(recharge.target); > + if (!mm) > + return; > + > + lru_add_drain_all(); > + down_read(&mm->mmap_sem); > + for (vma = mm->mmap; vma; vma = vma->vm_next) { > + int ret; > + struct mm_walk mem_cgroup_recharge_walk = { > + .pmd_entry = mem_cgroup_recharge_pte_range, > + .mm = mm, > + .private = vma, > + }; > + if (is_vm_hugetlb_page(vma)) > + continue; > + ret = walk_page_range(vma->vm_start, vma->vm_end, > + &mem_cgroup_recharge_walk); At _this_ point, check VM_SHARED and skip scan is a sane operation. Could you add checks ? > + if (ret) > + /* > + * means we have consumed all precharges and failed in > + * doing additional precharge. Just abandon here. > + */ > + break; > + cond_resched(); > + } > + up_read(&mm->mmap_sem); > + > + mmput(mm); > } > > static void mem_cgroup_move_task(struct cgroup_subsys *ss, > @@ -3458,8 +3725,10 @@ static void mem_cgroup_move_task(struct cgroup_subsys *ss, > struct mem_cgroup *mem = mem_cgroup_from_cont(cont); > > mutex_unlock(&memcg_tasklist); > - if (mem->recharge_at_immigrate && thread_group_leader(p)) > + if (mem->recharge_at_immigrate && thread_group_leader(p)) { > mem_cgroup_recharge(); > + mem_cgroup_clear_recharge(); > + } Is it guranteed that thread_group_leader(p) is true if this is true at can_attach() ? If no, if (.....) { mem_cgroup_recharge() } mem_cgroup_cleare_recharge() is better. Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. 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