Messages in this thread | | | Subject | Re: [PATCH] mm: page_alloc: High-order per-cpu page allocator v4 | From | Vlastimil Babka <> | Date | Thu, 1 Dec 2016 15:27:28 +0100 |
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On 12/01/2016 03:24 PM, Mel Gorman wrote: > On Thu, Dec 01, 2016 at 02:41:29PM +0100, Vlastimil Babka wrote: >> On 12/01/2016 01:24 AM, Mel Gorman wrote: >> >> ... >> >> >> Hmm I think that if this hits, we don't decrease count/increase nr_freed and >> pcp->count will become wrong. > > Ok, I think you're right but I also think it's relatively trivial to fix > with > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 94808f565f74..8777aefc1b8e 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1134,13 +1134,13 @@ static void free_pcppages_bulk(struct zone *zone, int count, > if (unlikely(isolated_pageblocks)) > mt = get_pageblock_migratetype(page); > > + nr_freed += (1 << order); > + count -= (1 << order); > if (bulkfree_pcp_prepare(page)) > continue; > > __free_one_page(page, page_to_pfn(page), zone, order, mt); > trace_mm_page_pcpu_drain(page, order, mt); > - nr_freed += (1 << order); > - count -= (1 << order); > } while (count > 0 && --batch_free && !list_empty(list)); > } > spin_unlock(&zone->lock); > >> And if we are unlucky/doing full drain, all >> lists will get empty, but as count stays e.g. 1, we loop forever on the >> outer while()? >> > > Potentially yes. Granted the system is already in a bad state as pages > are being freed in a bad or unknown state but we haven't halted the > system for that in the past. > >> BTW, I think there's a similar problem (but not introduced by this patch) in >> rmqueue_bulk() and its >> >> if (unlikely(check_pcp_refill(page))) >> continue; >> > > Potentially yes. It's outside the scope of this patch but it needs > fixing. > > If you agree with the above fix, I'll roll it into a v5 and append > another patch for this issue.
Yeah, looks fine. Thanks.
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