From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wu Fengguang Subject: Re: [PATCH 4/5] writeback: per task dirty rate limit Date: Mon, 15 Aug 2011 22:21:41 +0800 Message-ID: <20110815142141.GC23601@localhost> References: <20110806084447.388624428@intel.com> <20110806094527.002914580@intel.com> <1312811234.10488.34.camel@twins> <20110808142318.GC22080@localhost> <20110813162826.GA1646@thinkpad> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="KsGdsel6WgEHnImy" Cc: Peter Zijlstra , "linux-fsdevel@vger.kernel.org" , Andrew Morton , Jan Kara , Christoph Hellwig , Dave Chinner , Greg Thelen , Minchan Kim , Vivek Goyal , linux-mm , LKML To: Andrea Righi Return-path: Content-Disposition: inline In-Reply-To: <20110813162826.GA1646@thinkpad> Sender: owner-linux-mm@kvack.org List-Id: linux-fsdevel.vger.kernel.org --KsGdsel6WgEHnImy Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Andrea, > > @@ -1158,6 +1160,15 @@ void balance_dirty_pages_ratelimited_nr( > > if (bdi->dirty_exceeded) > > ratelimit = 8; > > > > + preempt_disable(); > > + p = &__get_cpu_var(dirty_leaks); > > + if (*p > 0 && current->nr_dirtied < ratelimit) { > > + nr_pages_dirtied = min(*p, ratelimit - current->nr_dirtied); > > + *p -= nr_pages_dirtied; > > + current->nr_dirtied += nr_pages_dirtied; > > + } > > + preempt_enable(); > > + > > I think we are still leaking some dirty pages, when the condition is > false nr_pages_dirtied is just ignored. > > Why not doing something like this? > > current->nr_dirtied += nr_pages_dirtied; You must mean the above line. Sorry I failed to provide another patch before this one (attached this time). With that preparation patch, it effectively become equal to the logic below :) > if (current->nr_dirtied < ratelimit) { > p = &get_cpu_var(dirty_leaks); > if (*p > 0) { > nr_pages_dirtied = min(*p, ratelimit - > current->nr_dirtied); > *p -= nr_pages_dirtied; > } else > nr_pages_dirtied = 0; > put_cpu_var(dirty_leaks); > > current->nr_dirtied += nr_pages_dirtied; > } Thanks, Fengguang > > if (unlikely(current->nr_dirtied >= ratelimit)) > > balance_dirty_pages(mapping, current->nr_dirtied); > > } > > --- linux-next.orig/kernel/exit.c 2011-08-08 21:43:37.000000000 +0800 > > +++ linux-next/kernel/exit.c 2011-08-08 21:45:58.000000000 +0800 > > @@ -1039,6 +1039,8 @@ NORET_TYPE void do_exit(long code) > > validate_creds_for_do_exit(tsk); > > > > preempt_disable(); > > + if (tsk->nr_dirtied) > > + __this_cpu_add(dirty_leaks, tsk->nr_dirtied); > > exit_rcu(); > > /* causes final put_task_struct in finish_task_switch(). */ > > tsk->state = TASK_DEAD; --KsGdsel6WgEHnImy Content-Type: text/x-diff; charset=us-ascii Content-Disposition: attachment; filename="writeback-accurate-task-dirtied.patch" Subject: writeback: fix dirtied pages accounting on sub-page writes Date: Thu Apr 14 07:52:37 CST 2011 When dd in 512bytes, generic_perform_write() calls balance_dirty_pages_ratelimited() 8 times for the same page, but obviously the page is only dirtied once. Fix it by accounting nr_dirtied at page dirty time. This will allow further simplification of the balance_dirty_pages_ratelimited_nr() calls. Signed-off-by: Wu Fengguang --- mm/page-writeback.c | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) --- linux-next.orig/mm/page-writeback.c 2011-08-15 22:12:14.000000000 +0800 +++ linux-next/mm/page-writeback.c 2011-08-15 22:12:27.000000000 +0800 @@ -1211,8 +1211,6 @@ void balance_dirty_pages_ratelimited_nr( else ratelimit = min(ratelimit, 32 >> (PAGE_SHIFT - 10)); - current->nr_dirtied += nr_pages_dirtied; - preempt_disable(); /* * This prevents one CPU to accumulate too many dirtied pages without @@ -1711,6 +1709,7 @@ void account_page_dirtied(struct page *p __inc_bdi_stat(mapping->backing_dev_info, BDI_DIRTIED); task_dirty_inc(current); task_io_account_write(PAGE_CACHE_SIZE); + current->nr_dirtied++; } } EXPORT_SYMBOL(account_page_dirtied); --KsGdsel6WgEHnImy-- -- 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