On Wed 12-10-16 17:03:49, Minchan Kim wrote: > Currently, unreserve_highatomic_pageblock bails out if it found > highatomic pageblock regardless of really moving free pages > from the one so that it could mitigate unreserve logic's goal > which saves OOM of a process. > > This patch makes unreserve functions bail out only if it moves > some pages out of !highatomic free list to avoid such false > positive. > > Another potential problem is that by race between page freeing and > reserve highatomic function, pages could be in highatomic free list > even though the pageblock is !high atomic migratetype. In that case, > unreserve_highatomic_pageblock can be void if count of highatomic > reserve is less than pageblock_nr_pages. We could solve it simply > via draining all of reserved pages before the OOM. It would have > a safeguard role to exhuast reserved pages before converging to OOM. > > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx> > Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> > Acked-by: Vlastimil Babka <vbabka@xxxxxxx> Looks good to me as well. If the previous one is agreed to go to stable this one should go with it IMHO. Thanks! > --- > mm/page_alloc.c | 24 +++++++++++++++++------- > 1 file changed, 17 insertions(+), 7 deletions(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index fd2f0e1bffc4..163d7fa759a2 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2079,8 +2079,12 @@ static void reserve_highatomic_pageblock(struct page *page, struct zone *zone, > * potentially hurts the reliability of high-order allocations when under > * intense memory pressure but failed atomic allocations should be easier > * to recover from than an OOM. > + * > + * If @force is true, try to unreserve a pageblock even though highatomic > + * pageblock is exhausted. > */ > -static bool unreserve_highatomic_pageblock(const struct alloc_context *ac) > +static bool unreserve_highatomic_pageblock(const struct alloc_context *ac, > + bool force) > { > struct zonelist *zonelist = ac->zonelist; > unsigned long flags; > @@ -2092,8 +2096,12 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac) > > for_each_zone_zonelist_nodemask(zone, z, zonelist, ac->high_zoneidx, > ac->nodemask) { > - /* Preserve at least one pageblock */ > - if (zone->nr_reserved_highatomic <= pageblock_nr_pages) > + /* > + * Preserve at least one pageblock unless memory pressure > + * is really high. > + */ > + if (!force && zone->nr_reserved_highatomic <= > + pageblock_nr_pages) > continue; > > spin_lock_irqsave(&zone->lock, flags); > @@ -2138,8 +2146,10 @@ static bool unreserve_highatomic_pageblock(const struct alloc_context *ac) > */ > set_pageblock_migratetype(page, ac->migratetype); > ret = move_freepages_block(zone, page, ac->migratetype); > - spin_unlock_irqrestore(&zone->lock, flags); > - return ret; > + if (ret) { > + spin_unlock_irqrestore(&zone->lock, flags); > + return ret; > + } > } > spin_unlock_irqrestore(&zone->lock, flags); > } > @@ -3343,7 +3353,7 @@ __alloc_pages_direct_reclaim(gfp_t gfp_mask, unsigned int order, > * Shrink them them and try again > */ > if (!page && !drained) { > - unreserve_highatomic_pageblock(ac); > + unreserve_highatomic_pageblock(ac, false); > drain_all_pages(NULL); > drained = true; > goto retry; > @@ -3462,7 +3472,7 @@ should_reclaim_retry(gfp_t gfp_mask, unsigned order, > */ > if (*no_progress_loops > MAX_RECLAIM_RETRIES) { > /* Before OOM, exhaust highatomic_reserve */ > - return unreserve_highatomic_pageblock(ac); > + return unreserve_highatomic_pageblock(ac, true); > } > > /* > -- > 2.7.4 > -- Michal Hocko SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>