From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756037AbZDPAAB (ORCPT ); Wed, 15 Apr 2009 20:00:01 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752553AbZDOX7v (ORCPT ); Wed, 15 Apr 2009 19:59:51 -0400 Received: from fgwmail7.fujitsu.co.jp ([192.51.44.37]:43241 "EHLO fgwmail7.fujitsu.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752097AbZDOX7u (ORCPT ); Wed, 15 Apr 2009 19:59:50 -0400 Date: Thu, 16 Apr 2009 08:58:14 +0900 From: KAMEZAWA Hiroyuki To: Andrea Righi Cc: Ryo Tsuruta , menage@google.com, balbir@linux.vnet.ibm.com, guijianfeng@cn.fujitsu.com, agk@sourceware.org, akpm@linux-foundation.org, axboe@kernel.dk, baramsori72@gmail.com, chlunde@ping.uio.no, dave@linux.vnet.ibm.com, dpshah@google.com, eric.rannaud@gmail.com, fernando@oss.ntt.co.jp, taka@valinux.co.jp, lizf@cn.fujitsu.com, matt@bluehost.com, dradford@bluehost.com, ngupta@google.com, randy.dunlap@oracle.com, roberto@unbit.it, s-uchida@ap.jp.nec.com, subrata@linux.vnet.ibm.com, yoshikawa.takuya@oss.ntt.co.jp, containers@lists.linux-foundation.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 3/9] bio-cgroup controller Message-Id: <20090416085814.8b6d077f.kamezawa.hiroyu@jp.fujitsu.com> In-Reply-To: <20090415132356.GA19270@linux> References: <1239740480-28125-4-git-send-email-righi.andrea@gmail.com> <20090415111528.b796519a.kamezawa.hiroyu@jp.fujitsu.com> <20090415093716.GA5968@linux> <20090415.213850.226770691.ryov@valinux.co.jp> <20090415132356.GA19270@linux> Organization: FUJITSU Co. LTD. X-Mailer: Sylpheed 2.5.0 (GTK+ 2.10.14; i686-pc-mingw32) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 15 Apr 2009 15:23:57 +0200 Andrea Righi wrote: > On Wed, Apr 15, 2009 at 09:38:50PM +0900, Ryo Tsuruta wrote: > > Hi Andrea and Kamezawa-san, > > > > > Ryo, it would be great if you can look at this and fix/integrate into > > > the mainstream bio-cgroup. Otherwise I can try to to schedule this in my > > > work. > > > > O.K. I'll apply those fixes and post patches as soon as I can. > > > > Very good! I've just tested the bio_cgroup_id inclusion in > page_cgroup->flags. I'm posting the patch on-top-of my patchset. > > If you're interested, it should apply cleanly to the original > bio-cgroup, except for the get/put_cgroup_from_page() part. > > Thanks, > -Andrea > --- > bio-cgroup: encode bio_cgroup_id in page_cgroup->flags > > Encode the bio_cgroup_id into the flags argument of page_cgroup as > suggested by Kamezawa. > > Lower 16-bits of the flags attribute are used for the actual page_cgroup > flags. The rest is reserved to store the bio-cgroup id. > > This allows to save 4 bytes (in 32-bit architectures) or 8 bytes (in > 64-bit) for each page_cgroup element. > > Signed-off-by: Andrea Righi > --- > include/linux/biotrack.h | 2 +- > include/linux/page_cgroup.h | 24 +++++++++++++++++++++--- > mm/biotrack.c | 26 ++++++++++++-------------- > 3 files changed, 34 insertions(+), 18 deletions(-) > > diff --git a/include/linux/biotrack.h b/include/linux/biotrack.h > index 25b8810..4bd0242 100644 > --- a/include/linux/biotrack.h > +++ b/include/linux/biotrack.h > @@ -28,7 +28,7 @@ struct bio_cgroup { > > static inline void __init_bio_page_cgroup(struct page_cgroup *pc) > { > - pc->bio_cgroup_id = 0; > + page_cgroup_set_bio_id(pc, 0); > } > > extern struct cgroup *get_cgroup_from_page(struct page *page); > diff --git a/include/linux/page_cgroup.h b/include/linux/page_cgroup.h > index 00a49c5..af780a4 100644 > --- a/include/linux/page_cgroup.h > +++ b/include/linux/page_cgroup.h > @@ -16,12 +16,30 @@ struct page_cgroup { > #ifdef CONFIG_CGROUP_MEM_RES_CTLR > struct mem_cgroup *mem_cgroup; > #endif > -#ifdef CONFIG_CGROUP_BIO > - int bio_cgroup_id; > -#endif > struct list_head lru; /* per cgroup LRU list */ > }; > > +#ifdef CONFIG_CGROUP_BIO > +/* > + * use lower 16 bits for flags and reserve the rest for the bio-cgroup id > + */ > +#define BIO_CGROUP_ID_SHIFT (16) > +#define BIO_CGROUP_ID_BITS (8 * sizeof(unsigned long) - BIO_CGROUP_ID_SHIFT) > + > +static inline unsigned long page_cgroup_get_bio_id(struct page_cgroup *pc) > +{ > + return pc->flags >> BIO_CGROUP_ID_SHIFT; > +} > + > +static inline void page_cgroup_set_bio_id(struct page_cgroup *pc, > + unsigned long id) > +{ > + WARN_ON(id >= (1UL << BIO_CGROUP_ID_BITS)); > + pc->flags &= (1UL << BIO_CGROUP_ID_SHIFT) - 1; > + pc->flags |= (unsigned long)(id << BIO_CGROUP_ID_SHIFT); > +} > +#endif > + Ah, there is "Lock" bit in pc->flags and above "set" code does read-modify-write without lock_page_cgroup(). Could you use lock_page_cgroup() or cmpxchg ? (or using something magical technique ?) Thanks, -Kame > void __meminit pgdat_page_cgroup_init(struct pglist_data *pgdat); > void __init page_cgroup_init(void); > struct page_cgroup *lookup_page_cgroup(struct page *page); > diff --git a/mm/biotrack.c b/mm/biotrack.c > index 431056c..4cca3bf 100644 > --- a/mm/biotrack.c > +++ b/mm/biotrack.c > @@ -74,7 +74,7 @@ void bio_cgroup_set_owner(struct page *page, struct mm_struct *mm) > struct bio_cgroup *biog; > struct page_cgroup *pc; > > - WARN_ON_ONCE(test_bit(PG_locked, &page->flags)); > + WARN_ON_ONCE(!test_bit(PG_locked, &page->flags)); > > if (bio_cgroup_disabled()) > return; > @@ -82,7 +82,7 @@ void bio_cgroup_set_owner(struct page *page, struct mm_struct *mm) > if (unlikely(!pc)) > return; > > - pc->bio_cgroup_id = 0; /* 0: default bio_cgroup id */ > + __init_bio_page_cgroup(pc); > if (!mm) > return; > /* > @@ -95,11 +95,11 @@ void bio_cgroup_set_owner(struct page *page, struct mm_struct *mm) > goto out; > /* > * css_get(&bio->css) isn't called to increment the reference > - * count of this bio_cgroup "biog" so pc->bio_cgroup_id might turn > - * invalid even if this page is still active. > - * This approach is chosen to minimize the overhead. > + * count of this bio_cgroup "biog" so the bio-cgroup id might turn > + * invalid even if this page is still active. This approach is chosen > + * to minimize the overhead. > */ > - pc->bio_cgroup_id = biog->id; > + page_cgroup_set_bio_id(pc, biog->id); > out: > rcu_read_unlock(); > } > @@ -112,7 +112,7 @@ void bio_cgroup_reset_owner(struct page *page, struct mm_struct *mm) > /* > * A little trick: > * Just call bio_cgroup_set_owner() for pages which are already > - * active since the bio_cgroup_id member of page_cgroup can be > + * active since the bio-cgroup id member of page_cgroup can be > * updated without any locks. This is because an integer type of > * variable can be set a new value at once on modern cpus. > */ > @@ -148,12 +148,10 @@ void bio_cgroup_copy_owner(struct page *npage, struct page *opage) > opc = lookup_page_cgroup(opage); > if (unlikely(!opc)) > return; > - > /* > - * Do this without any locks. The reason is the same as > - * bio_cgroup_reset_owner(). > + * XXX: is it safe to do this without locking? > */ > - npc->bio_cgroup_id = opc->bio_cgroup_id; > + page_cgroup_set_bio_id(npc, page_cgroup_get_bio_id(opc)); > } > > /* Create a new bio-cgroup. */ > @@ -250,7 +248,7 @@ struct cgroup *get_cgroup_from_page(struct page *page) > if (!pc) > return NULL; > lock_page_cgroup(pc); > - biog = find_bio_cgroup(pc->bio_cgroup_id); > + biog = find_bio_cgroup(page_cgroup_get_bio_id(pc)); > if (biog) { > css_get(&biog->css); > cgrp = biog->css.cgroup; > @@ -268,7 +266,7 @@ void put_cgroup_from_page(struct page *page) > if (!pc) > return; > lock_page_cgroup(pc); > - biog = find_bio_cgroup(pc->bio_cgroup_id); > + biog = find_bio_cgroup(page_cgroup_get_bio_id(pc)); > if (biog) > css_put(&biog->css); > unlock_page_cgroup(pc); > @@ -283,7 +281,7 @@ int get_bio_cgroup_id(struct bio *bio) > > pc = lookup_page_cgroup(page); > if (pc) > - id = pc->bio_cgroup_id; > + id = page_cgroup_get_bio_id(pc); > return id; > } > EXPORT_SYMBOL(get_bio_cgroup_id);