> 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); > } > > nr_reclaimed += nr_freed; This one looks better: --- vmscan: raise the bar to PAGEOUT_IO_SYNC stalls Fix "system goes totally unresponsive with many dirty/writeback pages" problem: http://lkml.org/lkml/2010/4/4/86 The root cause 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(). In Andreas' case, 512MB/1024 = 512KB, this is way too low comparing to the 22MB writeback and 190MB dirty pages. There can easily be a continuous range of 512KB dirty/writeback pages in the LRU, which will trigger the wait logic. To make it worse, when there are 50MB writeback pages and USB 1.1 is writing them in 1MB/s, wait_on_page_writeback() may stuck for up to 50 seconds. So only enter sync write&wait when priority goes below DEF_PRIORITY/3, or 6.25% LRU. As the default dirty throttle ratio is 20%, sync write&wait will hardly be triggered by pure dirty pages. Signed-off-by: Wu Fengguang <fengguang.wu@xxxxxxxxx> --- mm/vmscan.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) --- linux-next.orig/mm/vmscan.c 2010-07-22 16:36:58.000000000 +0800 +++ linux-next/mm/vmscan.c 2010-07-22 17:03:47.000000000 +0800 @@ -1206,7 +1206,7 @@ static unsigned long shrink_inactive_lis * but that should be acceptable to the caller */ if (nr_freed < nr_taken && !current_is_kswapd() && - sc->lumpy_reclaim_mode) { + sc->lumpy_reclaim_mode && priority < DEF_PRIORITY / 3) { congestion_wait(BLK_RW_ASYNC, HZ/10); /* -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
