On Wed, 2013-01-09 at 22:41 +0100, Zlatko Calusic wrote: > From: Zlatko Calusic <[email protected]> > > Currently we take a short nap (HZ/10) and wait for congestion to clear > before taking another pass with lower priority in balance_pgdat(). But > we do that only for the highest zone that we encounter is unbalanced > and congested. > > This patch changes that to wait on all congested zones in a single > pass in the hope that it will save us some scanning that way. Also we > take a nap as soon as congested zone is encountered and sc.priority < > DEF_PRIORITY - 2 (aka kswapd in trouble).
But you still didn't explain what's the problem you meat and what scenario can get benefit from your change. > > Cc: Mel Gorman <[email protected]> > Cc: Hugh Dickins <[email protected]> > Cc: Minchan Kim <[email protected]> > Signed-off-by: Zlatko Calusic <[email protected]> > --- > The patch is against the mm tree. Make sure that > mm-avoid-calling-pgdat_balanced-needlessly.patch is applied first (not > yet in the mmotm tree). Tested on half a dozen systems with different > workloads for the last few days, working really well! > > mm/vmscan.c | 35 ++++++++++++----------------------- > 1 file changed, 12 insertions(+), 23 deletions(-) > > diff --git a/mm/vmscan.c b/mm/vmscan.c > index 002ade6..1c5d38a 100644 > --- a/mm/vmscan.c > +++ b/mm/vmscan.c > @@ -2565,7 +2565,6 @@ static unsigned long balance_pgdat(pg_data_t *pgdat, > int order, > int *classzone_idx) > { > bool pgdat_is_balanced = false; > - struct zone *unbalanced_zone; > int i; > int end_zone = 0; /* Inclusive. 0 = ZONE_DMA */ > unsigned long total_scanned; > @@ -2596,9 +2595,6 @@ loop_again: > > do { > unsigned long lru_pages = 0; > - int has_under_min_watermark_zone = 0; > - > - unbalanced_zone = NULL; > > /* > * Scan in the highmem->dma direction for the highest > @@ -2739,15 +2735,20 @@ loop_again: > } > > if (!zone_balanced(zone, testorder, 0, end_zone)) { > - unbalanced_zone = zone; > - /* > - * We are still under min water mark. This > - * means that we have a GFP_ATOMIC allocation > - * failure risk. Hurry up! > - */ > + if (total_scanned && sc.priority < DEF_PRIORITY - > 2) { > + /* OK, kswapd is getting into trouble. */ > if (!zone_watermark_ok_safe(zone, order, > min_wmark_pages(zone), end_zone, 0)) > - has_under_min_watermark_zone = 1; > + /* > + * We are still under min water mark. > + * This means that we have a GFP_ATOMIC > + * allocation failure risk. Hurry up! > + */ > + count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); > + else > + /* Take a nap if a zone is congested. */ > + wait_iff_congested(zone, BLK_RW_ASYNC, > HZ/10); > + } > } else { > /* > * If a zone reaches its high watermark, > @@ -2758,7 +2759,6 @@ loop_again: > */ > zone_clear_flag(zone, ZONE_CONGESTED); > } > - > } > > /* > @@ -2776,17 +2776,6 @@ loop_again: > } > > /* > - * OK, kswapd is getting into trouble. Take a nap, then take > - * another pass across the zones. > - */ > - if (total_scanned && (sc.priority < DEF_PRIORITY - 2)) { > - if (has_under_min_watermark_zone) > - count_vm_event(KSWAPD_SKIP_CONGESTION_WAIT); > - else if (unbalanced_zone) > - wait_iff_congested(unbalanced_zone, > BLK_RW_ASYNC, HZ/10); > - } > - > - /* > * We do this so kswapd doesn't build up large priorities for > * example when it is freeing in parallel with allocators. It > * matches the direct reclaim path behaviour in terms of impact > -- > 1.8.1 > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
