lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Thu, 22 Jul 2010 10:42:09 +0100 From: Mel Gorman <mel@....ul.ie> To: Wu Fengguang <fengguang.wu@...el.com> Cc: Christoph Hellwig <hch@...radead.org>, "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, "linux-fsdevel@...r.kernel.org" <linux-fsdevel@...r.kernel.org>, "linux-mm@...ck.org" <linux-mm@...ck.org>, Dave Chinner <david@...morbit.com>, Chris Mason <chris.mason@...cle.com>, Nick Piggin <npiggin@...e.de>, Rik van Riel <riel@...hat.com>, Johannes Weiner <hannes@...xchg.org>, KAMEZAWA Hiroyuki <kamezawa.hiroyu@...fujitsu.com>, KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>, Andrew Morton <akpm@...ux-foundation.org>, Andrea Arcangeli <aarcange@...hat.com>, Minchan Kim <minchan.kim@...il.com> Subject: Re: [PATCH 7/8] writeback: sync old inodes first in background writeback On Thu, Jul 22, 2010 at 04:52:10PM +0800, Wu Fengguang wrote: > > Some insight on how the other writeback changes that are being floated > > around might affect the number of dirty pages reclaim encounters would also > > be helpful. > > Here is an interesting related problem about the wait_on_page_writeback() call > inside shrink_page_list(): > > http://lkml.org/lkml/2010/4/4/86 > > The problem is, wait_on_page_writeback() is called too early in the > direct reclaim path, which blocks many random/unrelated processes when > some slow (USB stick) writeback is on the way. > > A simple dd can easily create a big range of dirty pages in the LRU > list. Therefore priority can easily go below (DEF_PRIORITY - 2) in a > typical desktop, which triggers the lumpy reclaim mode and hence > wait_on_page_writeback(). > Lumpy reclaim is for high-order allocations. A simple dd should not be triggering it regularly unless there was a lot of forking going on at the same time. Also, how would a random or unrelated process get blocked on writeback unless they were also doing high-order allocations? What was the source of the high-order allocations? > I proposed this patch at the time, which was confirmed to solve the problem: > > --- linux-next.orig/mm/vmscan.c 2010-06-24 14:32:03.000000000 +0800 > +++ linux-next/mm/vmscan.c 2010-07-22 16:12:34.000000000 +0800 > @@ -1650,7 +1650,7 @@ static void set_lumpy_reclaim_mode(int p > */ > if (sc->order > PAGE_ALLOC_COSTLY_ORDER) > sc->lumpy_reclaim_mode = 1; > - else if (sc->order && priority < DEF_PRIORITY - 2) > + else if (sc->order && priority < DEF_PRIORITY / 2) > sc->lumpy_reclaim_mode = 1; > else > sc->lumpy_reclaim_mode = 0; > > > However KOSAKI and Minchan raised concerns about raising the bar. > I guess this new patch is more problem oriented and acceptable: > > --- linux-next.orig/mm/vmscan.c 2010-07-22 16:36:58.000000000 +0800 > +++ linux-next/mm/vmscan.c 2010-07-22 16:39:57.000000000 +0800 > @@ -1217,7 +1217,8 @@ static unsigned long shrink_inactive_lis > count_vm_events(PGDEACTIVATE, nr_active); > > nr_freed += shrink_page_list(&page_list, sc, > - PAGEOUT_IO_SYNC); > + priority < DEF_PRIORITY / 3 ? > + PAGEOUT_IO_SYNC : PAGEOUT_IO_ASYNC); > } > I'm not seeing how this helps. It delays when lumpy reclaim waits on IO to clean contiguous ranges of pages. I'll read that full thread as I wasn't aware of it before. -- Mel Gorman Part-time Phd Student Linux Technology Center University of Limerick IBM Dublin Software Lab -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists