From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-wg0-f41.google.com (mail-wg0-f41.google.com [74.125.82.41]) by kanga.kvack.org (Postfix) with ESMTP id 1B3066B0035 for ; Tue, 5 Aug 2014 08:24:51 -0400 (EDT) Received: by mail-wg0-f41.google.com with SMTP id z12so919612wgg.12 for ; Tue, 05 Aug 2014 05:24:48 -0700 (PDT) Received: from mx2.suse.de (cantor2.suse.de. [195.135.220.15]) by mx.google.com with ESMTPS id bc1si3221894wjc.142.2014.08.05.05.24.42 for (version=TLSv1 cipher=ECDHE-RSA-RC4-SHA bits=128/128); Tue, 05 Aug 2014 05:24:42 -0700 (PDT) Date: Tue, 5 Aug 2014 14:24:34 +0200 From: Michal Hocko Subject: Re: [patch] mm: memcontrol: avoid charge statistics churn during page migration Message-ID: <20140805122434.GD15908@dhcp22.suse.cz> References: <1407184469-20741-1-git-send-email-hannes@cmpxchg.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1407184469-20741-1-git-send-email-hannes@cmpxchg.org> Sender: owner-linux-mm@kvack.org List-ID: To: Johannes Weiner Cc: Andrew Morton , Hugh Dickins , linux-mm@kvack.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org On Mon 04-08-14 16:34:29, Johannes Weiner wrote: > Charge migration currently disables IRQs twice to update the charge > statistics for the old page and then again for the new page. > > But migration is a seemless transition of a charge from one physical > page to another one of the same size, so this should be a non-event > from an accounting point of view. Leave the statistics alone. Moving stats to mem_cgroup_commit_charge sounds logical to me but does this work properly even for the fuse replace page cache case when old and new pages can already live in different memcgs? > Signed-off-by: Johannes Weiner > --- > mm/memcontrol.c | 35 ++++++++++------------------------- > 1 file changed, 10 insertions(+), 25 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index 475ecadd9646..8d65dadeec1b 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -2728,7 +2728,7 @@ static void unlock_page_lru(struct page *page, int isolated) > } > > static void commit_charge(struct page *page, struct mem_cgroup *memcg, > - unsigned int nr_pages, bool lrucare) > + bool lrucare) > { > struct page_cgroup *pc = lookup_page_cgroup(page); > int isolated; > @@ -2765,16 +2765,6 @@ static void commit_charge(struct page *page, struct mem_cgroup *memcg, > > if (lrucare) > unlock_page_lru(page, isolated); > - > - local_irq_disable(); > - mem_cgroup_charge_statistics(memcg, page, nr_pages); > - /* > - * "charge_statistics" updated event counter. Then, check it. > - * Insert ancestor (and ancestor's ancestors), to softlimit RB-tree. > - * if they exceeds softlimit. > - */ > - memcg_check_events(memcg, page); > - local_irq_enable(); > } > > static DEFINE_MUTEX(set_limit_mutex); > @@ -6460,12 +6450,17 @@ void mem_cgroup_commit_charge(struct page *page, struct mem_cgroup *memcg, > if (!memcg) > return; > > + commit_charge(page, memcg, lrucare); > + > if (PageTransHuge(page)) { > nr_pages <<= compound_order(page); > VM_BUG_ON_PAGE(!PageTransHuge(page), page); > } > > - commit_charge(page, memcg, nr_pages, lrucare); > + local_irq_disable(); > + mem_cgroup_charge_statistics(memcg, page, nr_pages); > + memcg_check_events(memcg, page); > + local_irq_enable(); > > if (do_swap_account && PageSwapCache(page)) { > swp_entry_t entry = { .val = page_private(page) }; > @@ -6651,7 +6646,6 @@ void mem_cgroup_uncharge_list(struct list_head *page_list) > void mem_cgroup_migrate(struct page *oldpage, struct page *newpage, > bool lrucare) > { > - unsigned int nr_pages = 1; > struct page_cgroup *pc; > int isolated; > > @@ -6660,6 +6654,8 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage, > VM_BUG_ON_PAGE(!lrucare && PageLRU(oldpage), oldpage); > VM_BUG_ON_PAGE(!lrucare && PageLRU(newpage), newpage); > VM_BUG_ON_PAGE(PageAnon(oldpage) != PageAnon(newpage), newpage); > + VM_BUG_ON_PAGE(PageTransHuge(oldpage) != PageTransHuge(newpage), > + newpage); > > if (mem_cgroup_disabled()) > return; > @@ -6677,12 +6673,6 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage, > VM_BUG_ON_PAGE(!(pc->flags & PCG_MEM), oldpage); > VM_BUG_ON_PAGE(do_swap_account && !(pc->flags & PCG_MEMSW), oldpage); > > - if (PageTransHuge(oldpage)) { > - nr_pages <<= compound_order(oldpage); > - VM_BUG_ON_PAGE(!PageTransHuge(oldpage), oldpage); > - VM_BUG_ON_PAGE(!PageTransHuge(newpage), newpage); > - } > - > if (lrucare) > lock_page_lru(oldpage, &isolated); > > @@ -6691,12 +6681,7 @@ void mem_cgroup_migrate(struct page *oldpage, struct page *newpage, > if (lrucare) > unlock_page_lru(oldpage, isolated); > > - local_irq_disable(); > - mem_cgroup_charge_statistics(pc->mem_cgroup, oldpage, -nr_pages); > - memcg_check_events(pc->mem_cgroup, oldpage); > - local_irq_enable(); > - > - commit_charge(newpage, pc->mem_cgroup, nr_pages, lrucare); > + commit_charge(newpage, pc->mem_cgroup, lrucare); > } > > /* > -- > 2.0.3 > -- Michal Hocko SUSE Labs -- 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/ . Don't email: email@kvack.org