From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail138.messagelabs.com (mail138.messagelabs.com [216.82.249.35]) by kanga.kvack.org (Postfix) with ESMTP id 580066B005A for ; Thu, 11 Jun 2009 07:13:22 -0400 (EDT) Date: Thu, 11 Jun 2009 12:13:42 +0100 From: Mel Gorman Subject: Re: [PATCH for mmotm 2/5] Message-ID: <20090611111341.GE7302@csn.ul.ie> References: <20090611192114.6D4A.A69D9226@jp.fujitsu.com> <20090611192600.6D50.A69D9226@jp.fujitsu.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20090611192600.6D50.A69D9226@jp.fujitsu.com> Sender: owner-linux-mm@kvack.org To: KOSAKI Motohiro Cc: linux-mm , LKML , Wu Fengguang , Andrew Morton List-ID: On Thu, Jun 11, 2009 at 07:26:48PM +0900, KOSAKI Motohiro wrote: > Changes since Wu's original patch > - adding vmstat > - rename NR_TMPFS_MAPPED to NR_SWAP_BACKED_FILE_MAPPED > > > ---------------------- > Subject: [PATCH] introduce NR_SWAP_BACKED_FILE_MAPPED zone stat This got lost in the actual subject line. > Desirable zone reclaim implementaion want to know the number of > file-backed and unmapped pages. > There needs to be more justification for this. We need an example failure case that this addresses. For example, Patch 1 of my series was to address the following problem included with the patchset leader "The reported problem was that malloc() stalled for a long time (minutes in some cases) if a large tmpfs mount was occupying a large percentage of memory overall. The pages did not get cleaned or reclaimed by zone_reclaim() because the zone_reclaim_mode was unsuitable, but the lists are uselessly scanned frequencly making the CPU spin at near 100%." We should have a similar case. What "desirable" zone_reclaim() should be spelled out as well. Minimally something like "For zone_reclaim() to be efficient, it must be able to detect in advance if the LRU scan will reclaim the necessary pages with the limitations of the current zone_reclaim_mode. Otherwise, the CPU usage is increases as zone_reclaim() uselessly scans the LRU list. The problem with the heuristic is .... This patch fixes the heuristic by ...." etc? I'm not trying to be awkward. I believe I provided similar reasoning with my own patchset. > Thus, we need to know number of swap-backed mapped pages for > calculate above number. > > > Cc: Mel Gorman > Signed-off-by: Wu Fengguang > Signed-off-by: KOSAKI Motohiro > --- > include/linux/mmzone.h | 2 ++ > mm/rmap.c | 7 +++++++ > mm/vmstat.c | 1 + > 3 files changed, 10 insertions(+) > > Index: b/include/linux/mmzone.h > =================================================================== > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -88,6 +88,8 @@ enum zone_stat_item { > NR_ANON_PAGES, /* Mapped anonymous pages */ > NR_FILE_MAPPED, /* pagecache pages mapped into pagetables. > only modified from process context */ > + NR_SWAP_BACKED_FILE_MAPPED, /* Similar to NR_FILE_MAPPED. but > + only account swap-backed pages */ > NR_FILE_PAGES, > NR_FILE_DIRTY, > NR_WRITEBACK, > Index: b/mm/rmap.c > =================================================================== > --- a/mm/rmap.c > +++ b/mm/rmap.c > @@ -829,6 +829,10 @@ void page_add_file_rmap(struct page *pag > { > if (atomic_inc_and_test(&page->_mapcount)) { > __inc_zone_page_state(page, NR_FILE_MAPPED); > + if (PageSwapBacked(page)) > + __inc_zone_page_state(page, > + NR_SWAP_BACKED_FILE_MAPPED); > + > mem_cgroup_update_mapped_file_stat(page, 1); > } > } > @@ -884,6 +888,9 @@ void page_remove_rmap(struct page *page) > __dec_zone_page_state(page, NR_ANON_PAGES); > } else { > __dec_zone_page_state(page, NR_FILE_MAPPED); > + if (PageSwapBacked(page)) > + __dec_zone_page_state(page, > + NR_SWAP_BACKED_FILE_MAPPED); > } > mem_cgroup_update_mapped_file_stat(page, -1); > /* > Index: b/mm/vmstat.c > =================================================================== > --- a/mm/vmstat.c > +++ b/mm/vmstat.c > @@ -633,6 +633,7 @@ static const char * const vmstat_text[] > "nr_mlock", > "nr_anon_pages", > "nr_mapped", > + "nr_swap_backed_file_mapped", > "nr_file_pages", > "nr_dirty", > "nr_writeback", > Otherwise the patch seems reasonable. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- 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