> When a high-order allocation fails, kswapd is kicked so that it reclaims > at a higher-order to avoid direct reclaimers stall and to help GFP_ATOMIC > allocations. Something has changed in recent kernels that affect the timing > where high-order GFP_ATOMIC allocations are now failing with more frequency, > particularly under pressure. > > This patch pre-emptively checks if watermarks have been hit after a > high-order allocation completes successfully. If the watermarks have been > reached, kswapd is woken in the hope it fixes the watermarks before the > next GFP_ATOMIC allocation fails. > > Warning, this patch is somewhat of a band-aid. If this makes a difference, > it still implies that something has changed that is either causing more > GFP_ATOMIC allocations to occur (such as the case with iwlagn wireless > driver) or make them more likely to fail.
hmm, I'm confused. this description addressed generic high order allocation. but, > > Signed-off-by: Mel Gorman <[email protected]> > --- > mm/page_alloc.c | 33 ++++++++++++++++++++++----------- > 1 files changed, 22 insertions(+), 11 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 7f2aa3e..851df40 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1596,6 +1596,17 @@ try_next_zone: > return page; > } > > +static inline > +void wake_all_kswapd(unsigned int order, struct zonelist *zonelist, > + enum zone_type high_zoneidx) > +{ > + struct zoneref *z; > + struct zone *zone; > + > + for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) > + wakeup_kswapd(zone, order); > +} > + > static inline int > should_alloc_retry(gfp_t gfp_mask, unsigned int order, > unsigned long pages_reclaimed) > @@ -1730,18 +1741,18 @@ __alloc_pages_high_priority(gfp_t gfp_mask, unsigned > int order, __alloc_pages_high_priority() is only called if ALLOC_NO_WATERMARKS. ALLOC_NO_WATERMARKS mean PF_MEMALLOC or TIF_MEMDIE and GFP_ATOMIC don't make nested alloc_pages() (= don't make PF_MEMALLOC case). Then, I haven't understand why this patch improve iwlagn GFP_ATOMIC case. hmm, maybe I missed something. I see the code again tommorow. > congestion_wait(BLK_RW_ASYNC, HZ/50); > } while (!page && (gfp_mask & __GFP_NOFAIL)); > > - return page; > -} > - > -static inline > -void wake_all_kswapd(unsigned int order, struct zonelist *zonelist, > - enum zone_type high_zoneidx) > -{ > - struct zoneref *z; > - struct zone *zone; > + /* > + * If after a high-order allocation we are now below watermarks, > + * pre-emptively kick kswapd rather than having the next allocation > + * fail and have to wake up kswapd, potentially failing GFP_ATOMIC > + * allocations or entering direct reclaim > + */ > + if (unlikely(order) && page && !zone_watermark_ok(preferred_zone, order, > + preferred_zone->watermark[ALLOC_WMARK_LOW], > + zone_idx(preferred_zone), ALLOC_WMARK_LOW)) > + wake_all_kswapd(order, zonelist, high_zoneidx); > > - for_each_zone_zonelist(zone, z, zonelist, high_zoneidx) > - wakeup_kswapd(zone, order); > + return page; > } > > static inline int > -- > 1.6.3.3 > > -- > To unsubscribe, send a message with 'unsubscribe linux-mm' in > the body to [email protected]. For more info on Linux MM, > see: http://www.linux-mm.org/ . > Don't email: <a href=mailto:"[email protected]";> [email protected] </a> -- To unsubscribe from this list: send the line "unsubscribe kernel-testers" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html
