From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from psmtp.com (na3sys010amx198.postini.com [74.125.245.198]) by kanga.kvack.org (Postfix) with SMTP id F163F6B0072 for ; Wed, 2 Jan 2013 04:08:08 -0500 (EST) Date: Wed, 2 Jan 2013 10:08:03 +0100 From: Michal Hocko Subject: Re: [PATCH V3 2/8] Make TestSetPageDirty and dirty page accounting in one func Message-ID: <20130102090803.GB22160@dhcp22.suse.cz> References: <1356455919-14445-1-git-send-email-handai.szj@taobao.com> <1356456156-14535-1-git-send-email-handai.szj@taobao.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1356456156-14535-1-git-send-email-handai.szj@taobao.com> Sender: owner-linux-mm@kvack.org List-ID: To: Sha Zhengju Cc: linux-kernel@vger.kernel.org, cgroups@vger.kernel.org, linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, dchinner@redhat.com, akpm@linux-foundation.org, kamezawa.hiroyu@jp.fujitsu.com, gthelen@google.com, fengguang.wu@intel.com, glommer@parallels.com, Sha Zhengju On Wed 26-12-12 01:22:36, Sha Zhengju wrote: > From: Sha Zhengju > > Commit a8e7d49a(Fix race in create_empty_buffers() vs __set_page_dirty_buffers()) > extracts TestSetPageDirty from __set_page_dirty and is far away from > account_page_dirtied. But it's better to make the two operations in one single > function to keep modular. So in order to avoid the potential race mentioned in > commit a8e7d49a, we can hold private_lock until __set_page_dirty completes. > There's no deadlock between ->private_lock and ->tree_lock after confirmation. Could you be more specific here? E.g. quote mm/filemap.c comment I have mentioned during the first round of review? > It's a prepare patch for following memcg dirty page accounting patches. > > > Here is some test numbers that before/after this patch: > Test steps(Mem-4g, ext4): > drop_cache; sync > fio (ioengine=sync/write/buffered/bs=4k/size=1g/numjobs=2/group_reporting/thread) Could also add some rationale why you think this test is relevant? > We test it for 10 times and get the average numbers: > Before: > write: io=2048.0MB, bw=254117KB/s, iops=63528.9 , runt= 8279msec > lat (usec): min=1 , max=742361 , avg=30.918, stdev=1601.02 > After: > write: io=2048.0MB, bw=254044KB/s, iops=63510.3 , runt= 8274.4msec > lat (usec): min=1 , max=856333 , avg=31.043, stdev=1769.32 > > Note that the impact is little(<1%). > > > Signed-off-by: Sha Zhengju > Reviewed-by: Michal Hocko > --- > fs/buffer.c | 24 ++++++++++++------------ > 1 file changed, 12 insertions(+), 12 deletions(-) > > diff --git a/fs/buffer.c b/fs/buffer.c > index c017a2d..3b032b9 100644 > --- a/fs/buffer.c > +++ b/fs/buffer.c > @@ -609,9 +609,15 @@ EXPORT_SYMBOL(mark_buffer_dirty_inode); > * If warn is true, then emit a warning if the page is not uptodate and has > * not been truncated. > */ > -static void __set_page_dirty(struct page *page, > +static int __set_page_dirty(struct page *page, > struct address_space *mapping, int warn) > { > + if (unlikely(!mapping)) > + return !TestSetPageDirty(page); > + > + if (TestSetPageDirty(page)) > + return 0; > + > spin_lock_irq(&mapping->tree_lock); > if (page->mapping) { /* Race with truncate? */ > WARN_ON_ONCE(warn && !PageUptodate(page)); > @@ -621,6 +627,8 @@ static void __set_page_dirty(struct page *page, > } > spin_unlock_irq(&mapping->tree_lock); > __mark_inode_dirty(mapping->host, I_DIRTY_PAGES); > + > + return 1; > } > > /* > @@ -666,11 +674,9 @@ int __set_page_dirty_buffers(struct page *page) > bh = bh->b_this_page; > } while (bh != head); > } > - newly_dirty = !TestSetPageDirty(page); > + newly_dirty = __set_page_dirty(page, mapping, 1); > spin_unlock(&mapping->private_lock); > > - if (newly_dirty) > - __set_page_dirty(page, mapping, 1); > return newly_dirty; > } > EXPORT_SYMBOL(__set_page_dirty_buffers); > @@ -1125,14 +1131,8 @@ void mark_buffer_dirty(struct buffer_head *bh) > return; > } > > - if (!test_set_buffer_dirty(bh)) { > - struct page *page = bh->b_page; > - if (!TestSetPageDirty(page)) { > - struct address_space *mapping = page_mapping(page); > - if (mapping) > - __set_page_dirty(page, mapping, 0); > - } > - } > + if (!test_set_buffer_dirty(bh)) > + __set_page_dirty(bh->b_page, page_mapping(bh->b_page), 0); > } > EXPORT_SYMBOL(mark_buffer_dirty); > > -- > 1.7.9.5 > -- 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