From mboxrd@z Thu Jan 1 00:00:00 1970 From: KAMEZAWA Hiroyuki Subject: Re: [RFC][PATCH 3/3] memcg: atomic update of memcg pointer and other bits. Date: Fri, 23 Mar 2012 10:03:13 +0900 Message-ID: <4F6BCBD1.1030602@jp.fujitsu.com> References: <4F66E6A5.10804@jp.fujitsu.com> <4F66E85E.6030000@jp.fujitsu.com> <20120322133820.GE18665@tiehlicka.suse.cz> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <20120322133820.GE18665@tiehlicka.suse.cz> Sender: owner-linux-mm@kvack.org List-ID: Content-Type: text/plain; charset="us-ascii" To: Michal Hocko Cc: linux-mm@kvack.org, cgroups@vger.kernel.org, Johannes Weiner , Hugh Dickins , Han Ying , Glauber Costa , "Aneesh Kumar K.V" , Andrew Morton , suleiman@google.com, n-horiguchi@ah.jp.nec.com, khlebnikov@openvz.org, Tejun Heo (2012/03/22 22:38), Michal Hocko wrote: > On Mon 19-03-12 17:03:42, KAMEZAWA Hiroyuki wrote: > [...] >> @@ -1237,8 +1237,6 @@ mem_cgroup_get_reclaim_stat_from_page(struct page *page) >> pc = lookup_page_cgroup(page); >> if (!PageCgroupUsed(pc)) >> return NULL; >> - /* Ensure pc's mem_cgroup is visible after reading PCG_USED. */ >> - smp_rmb(); >> mz = page_cgroup_zoneinfo(pc_to_mem_cgroup(pc), page); >> return &mz->reclaim_stat; >> } >> @@ -2491,16 +2489,7 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg, >> } >> } >> >> - pc_set_mem_cgroup(pc, memcg); >> - /* >> - * We access a page_cgroup asynchronously without lock_page_cgroup(). >> - * Especially when a page_cgroup is taken from a page, pc's mem_cgroup >> - * is accessed after testing USED bit. To make pc's mem_cgroup visible >> - * before USED bit, we need memory barrier here. >> - * See mem_cgroup_add_lru_list(), etc. >> - */ >> - smp_wmb(); >> - SetPageCgroupUsed(pc); >> + pc_set_mem_cgroup(pc, memcg, BIT(PCG_USED) | BIT(PCG_LOCK)); > > This is not nice. Maybe we need two variants (pc_set_mem_cgroup[_flags])? > Sure. I'll add that. >> if (lrucare) { >> if (was_on_lru) { >> @@ -2529,7 +2518,6 @@ static void __mem_cgroup_commit_charge(struct mem_cgroup *memcg, >> >> #ifdef CONFIG_TRANSPARENT_HUGEPAGE >> >> -#define PCGF_NOCOPY_AT_SPLIT ((1 << PCG_LOCK) | (1 << PCG_MIGRATION)) >> /* >> * Because tail pages are not marked as "used", set it. We're under >> * zone->lru_lock, 'splitting on pmd' and compound_lock. >> @@ -2547,9 +2535,7 @@ void mem_cgroup_split_huge_fixup(struct page *head) >> return; >> for (i = 1; i < HPAGE_PMD_NR; i++) { >> pc = head_pc + i; >> - pc_set_mem_cgroup(pc, memcg); >> - smp_wmb();/* see __commit_charge() */ >> - pc->flags = head_pc->flags & ~PCGF_NOCOPY_AT_SPLIT; >> + pc_set_mem_cgroup(pc, memcg, BIT(PCG_USED)); > > Maybe it would be cleaner to remove PCGF_NOCOPY_AT_SPLIT in a separate patch with > VM_BUG_ON(!head_pc->flags & BIT(PCG_USED))? > Hm, ok. I'll divide this patch. >> } >> } >> #endif /* CONFIG_TRANSPARENT_HUGEPAGE */ >> @@ -2616,7 +2602,7 @@ static int mem_cgroup_move_account(struct page *page, >> __mem_cgroup_cancel_charge(from, nr_pages); >> >> /* caller should have done css_get */ >> - pc_set_mem_cgroup(pc, to); >> + pc_set_mem_cgroup(pc, to, BIT(PCG_USED) | BIT(PCG_LOCK)); > > Same here. > pc_set_mem_cgroup_flags() ? Thanks, -Kame -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org