On 09/29/2007 07:04 AM, Fengguang Wu wrote: > On Thu, Sep 27, 2007 at 11:32:36PM -0700, Chakri n wrote: >> Hi, >> >> In my testing, a unresponsive file system can hang all I/O in the system. >> This is not seen in 2.4. >> >> I started 20 threads doing I/O on a NFS share. They are just doing 4K >> writes in a loop. >> >> Now I stop NFS server hosting the NFS share and start a >> "dd" process to write a file on local EXT3 file system. >> >> # dd if=/dev/zero of=/tmp/x count=1000 >> >> This process never progresses. > > Peter, do you think this patch will help? > > === > writeback: avoid possible balance_dirty_pages() lockup on light-load bdi > > On a busy-writing system, a writer could be hold up infinitely on a > light-load device. It will be trying to sync more than enough dirty data. > > The problem case: > > 0. sda/nr_dirty >= dirty_limit; > sdb/nr_dirty == 0 > 1. dd writes 32 pages on sdb > 2. balance_dirty_pages() blocks dd, and tries to write 6MB. > 3. it never gets there: there's only 128KB dirty data. > 4. dd may be blocked for a loooong time as long as sda is overloaded > > Fix it by returning on 'zero dirty inodes' in the current bdi. > (In fact there are slight differences between 'dirty inodes' and 'dirty pages'. > But there is no available counters for 'dirty pages'.) > > Cc: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx> > Signed-off-by: Fengguang Wu <wfg@xxxxxxxxxxxxxxxx> > --- > mm/page-writeback.c | 3 +++ > 1 file changed, 3 insertions(+) > > --- linux-2.6.22.orig/mm/page-writeback.c > +++ linux-2.6.22/mm/page-writeback.c > @@ -227,6 +227,9 @@ static void balance_dirty_pages(struct a > if (nr_reclaimable + global_page_state(NR_WRITEBACK) <= > dirty_thresh) > break; > + if (list_empty(&mapping->host->i_sb->s_dirty) && > + list_empty(&mapping->host->i_sb->s_io)) > + break; > > if (!dirty_exceeded) > dirty_exceeded = 1; > This looks better than the other candidate to fix the problem. Are we going to fix 2.6.23 before release? Multiple people have reported this problem now... _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
