Thanks David.
On 8/11/2020 1:06 AM, David Rientjes wrote:
> On Mon, 10 Aug 2020, Charan Teja Reddy wrote:
>
>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
>> index e4896e6..25e7e12 100644
>> --- a/mm/page_alloc.c
>> +++ b/mm/page_alloc.c
>> @@ -3106,6 +3106,7 @@ static void free_unref_page_commit(struct page *page,
>> unsigned long pfn)
>> struct zone *zone = page_zone(page);
>> struct per_cpu_pages *pcp;
>> int migratetype;
>> + int high;
>>
>> migratetype = get_pcppage_migratetype(page);
>> __count_vm_event(PGFREE);
>> @@ -3128,8 +3129,19 @@ static void free_unref_page_commit(struct page *page,
>> unsigned long pfn)
>> pcp = &this_cpu_ptr(zone->pageset)->pcp;
>> list_add(&page->lru, &pcp->lists[migratetype]);
>> pcp->count++;
>> - if (pcp->count >= pcp->high) {
>> - unsigned long batch = READ_ONCE(pcp->batch);
>> + high = READ_ONCE(pcp->high);
>> + if (pcp->count >= high) {
>> + int batch;
>> +
>> + batch = READ_ONCE(pcp->batch);
>> + /*
>> + * For non-default pcp struct values, high is always
>> + * greater than the batch. If high < batch then pass
>> + * proper count to free the pcp's list pages.
>> + */
>> + if (unlikely(high < batch))
>> + batch = min(pcp->count, batch);
>> +
>> free_pcppages_bulk(zone, batch, pcp);
>> }
>> }
>
> I'm wondering if a fix to free_pcppages_bulk() is more appropriate here
> because the count passed into it seems otherwise fragile if this results
> in a hung core?
>
Agree that the free_pcppages_bulk() is appropriate place to fix and it
actually much cleaner. Raised V2:
https://patchwork.kernel.org/patch/11709225/
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