From mboxrd@z Thu Jan 1 00:00:00 1970 From: akpm@linux-foundation.org Subject: - kswapd-should-only-wait-on-io-if-there-is-io.patch removed from -mm tree Date: Fri, 08 Feb 2008 00:03:44 -0800 Message-ID: <200802080803.m1883PS7014122@imap1.linux-foundation.org> Reply-To: linux-kernel@vger.kernel.org Return-path: Received: from smtp2.linux-foundation.org ([207.189.120.14]:52251 "EHLO smtp2.linux-foundation.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1761794AbYBHIT6 (ORCPT ); Fri, 8 Feb 2008 03:19:58 -0500 Sender: mm-commits-owner@vger.kernel.org List-Id: mm-commits@vger.kernel.org To: riel@redhat.com, mm-commits@vger.kernel.org The patch titled kswapd should only wait on IO if there is IO has been removed from the -mm tree. Its filename was kswapd-should-only-wait-on-io-if-there-is-io.patch This patch was dropped because it was merged into mainline or a subsystem tree The current -mm tree may be found at http://userweb.kernel.org/~akpm/mmotm/ ------------------------------------------------------ Subject: kswapd should only wait on IO if there is IO From: Rik van Riel The current kswapd (and try_to_free_pages) code has an oddity where the code will wait on IO, even if there is no IO in flight. This problem is notable especially when the system scans through many unfreeable pages, causing unnecessary stalls in the VM. Additionally, tasks without __GFP_FS or __GFP_IO in the direct reclaim path will sleep if a significant number of pages are encountered that should be written out. This gives kswapd a chance to write out those pages, while the direct reclaim task sleeps. Signed-off-by: Rik van Riel Signed-off-by: Andrew Morton --- mm/vmscan.c | 27 ++++++++++++++++++++++----- 1 file changed, 22 insertions(+), 5 deletions(-) diff -puN mm/vmscan.c~kswapd-should-only-wait-on-io-if-there-is-io mm/vmscan.c --- a/mm/vmscan.c~kswapd-should-only-wait-on-io-if-there-is-io +++ a/mm/vmscan.c @@ -70,6 +70,13 @@ struct scan_control { int order; + /* + * Pages that have (or should have) IO pending. If we run into + * a lot of these, we're better off waiting a little for IO to + * finish rather than scanning more pages in the VM. + */ + int nr_io_pages; + /* Which cgroup do we reclaim from */ struct mem_cgroup *mem_cgroup; @@ -499,8 +506,10 @@ static unsigned long shrink_page_list(st */ if (sync_writeback == PAGEOUT_IO_SYNC && may_enter_fs) wait_on_page_writeback(page); - else + else { + sc->nr_io_pages++; goto keep_locked; + } } referenced = page_referenced(page, 1, sc->mem_cgroup); @@ -539,8 +548,10 @@ static unsigned long shrink_page_list(st if (PageDirty(page)) { if (sc->order <= PAGE_ALLOC_COSTLY_ORDER && referenced) goto keep_locked; - if (!may_enter_fs) + if (!may_enter_fs) { + sc->nr_io_pages++; goto keep_locked; + } if (!sc->may_writepage) goto keep_locked; @@ -551,8 +562,10 @@ static unsigned long shrink_page_list(st case PAGE_ACTIVATE: goto activate_locked; case PAGE_SUCCESS: - if (PageWriteback(page) || PageDirty(page)) + if (PageWriteback(page) || PageDirty(page)) { + sc->nr_io_pages++; goto keep; + } /* * A synchronous write - probably a ramdisk. Go * ahead and try to reclaim the page. @@ -1259,6 +1272,7 @@ static unsigned long do_try_to_free_page for (priority = DEF_PRIORITY; priority >= 0; priority--) { sc->nr_scanned = 0; + sc->nr_io_pages = 0; if (!priority) disable_swap_token(); nr_reclaimed += shrink_zones(priority, zones, sc); @@ -1292,7 +1306,8 @@ static unsigned long do_try_to_free_page } /* Take a nap, wait for some writeback to complete */ - if (sc->nr_scanned && priority < DEF_PRIORITY - 2) + if (sc->nr_scanned && priority < DEF_PRIORITY - 2 && + sc->nr_io_pages > sc->swap_cluster_max) congestion_wait(WRITE, HZ/10); } /* top priority shrink_caches still had more to do? don't OOM, then */ @@ -1424,6 +1439,7 @@ loop_again: if (!priority) disable_swap_token(); + sc.nr_io_pages = 0; all_zones_ok = 1; /* @@ -1516,7 +1532,8 @@ loop_again: * OK, kswapd is getting into trouble. Take a nap, then take * another pass across the zones. */ - if (total_scanned && priority < DEF_PRIORITY - 2) + if (total_scanned && priority < DEF_PRIORITY - 2 && + sc.nr_io_pages > sc.swap_cluster_max) congestion_wait(WRITE, HZ/10); /* _ Patches currently in -mm which might be from riel@redhat.com are origin.patch vmscan-give-referenced-active-and-unmapped-pages-a-second-trip-around-the-lru.patch