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Date: Thu, 23 Jun 2016 13:21:57 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: David Rientjes <rientjes@...gle.com>,
Andrew Morton <akpm@...ux-foundation.org>
Cc: Minchan Kim <minchan@...nel.org>,
Joonsoo Kim <iamjoonsoo.kim@....com>,
Mel Gorman <mgorman@...hsingularity.net>,
Hugh Dickins <hughd@...gle.com>, linux-kernel@...r.kernel.org,
linux-mm@...ck.org, stable@...r.kernel.org
Subject: Re: [patch] mm, compaction: abort free scanner if split fails
On 06/23/2016 01:40 AM, David Rientjes wrote:
> On Wed, 22 Jun 2016, Andrew Morton wrote:
>
>> And
>> mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch
>> churns things around some more. Now this:
>>
>>
>> /* Found a free page, will break it into order-0 pages */
>> order = page_order(page);
>> isolated = __isolate_free_page(page, order);
>> set_page_private(page, order);
>> total_isolated += isolated;
>> list_add_tail(&page->lru, freelist);
>> cc->nr_freepages += isolated;
>> if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
>> blockpfn += isolated;
>> break;
>> }
>> /* Advance to the end of split page */
>> blockpfn += isolated - 1;
>> cursor += isolated - 1;
>> continue;
>>
>> isolate_fail:
>>
>> and things are looking a bit better...
>>
>
> This looks like it's missing the
>
> if (!isolated)
> break;
>
> check from mm-compaction-abort-free-scanner-if-split-fails.patch which is
> needed to properly terminate when the low watermark fails (and adding to
> freelist as Minchan mentioned before I saw this patch).
Agreed.
>
> I rebased
> mm-compaction-split-freepages-without-holding-the-zone-lock.patch as I
> thought it should be done and folded
> mm-compaction-split-freepages-without-holding-the-zone-lock-fix.patch into
> it for simplicity. I think this should replace
> mm-compaction-split-freepages-without-holding-the-zone-lock.patch in -mm.
Yes, it should replace both the .patch and the -fix.patch.
Thanks!
>
> From: Joonsoo Kim <iamjoonsoo.kim@....com>
>
> We don't need to split freepages with holding the zone lock. It will
> cause more contention on zone lock so not desirable.
>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@....com>
> Acked-by: Vlastimil Babka <vbabka@...e.cz>
> ---
> diff --git a/include/linux/mm.h b/include/linux/mm.h
> --- a/include/linux/mm.h
> +++ b/include/linux/mm.h
> @@ -537,7 +537,6 @@ void __put_page(struct page *page);
> void put_pages_list(struct list_head *pages);
>
> void split_page(struct page *page, unsigned int order);
> -int split_free_page(struct page *page);
>
> /*
> * Compound pages have a destructor function. Provide a
> diff --git a/mm/compaction.c b/mm/compaction.c
> index ab21497..9d17b21 100644
> --- a/mm/compaction.c
> +++ b/mm/compaction.c
> @@ -65,13 +65,31 @@ static unsigned long release_freepages(struct list_head *freelist)
>
> static void map_pages(struct list_head *list)
> {
> - struct page *page;
> + unsigned int i, order, nr_pages;
> + struct page *page, *next;
> + LIST_HEAD(tmp_list);
> +
> + list_for_each_entry_safe(page, next, list, lru) {
> + list_del(&page->lru);
>
> - list_for_each_entry(page, list, lru) {
> - arch_alloc_page(page, 0);
> - kernel_map_pages(page, 1, 1);
> - kasan_alloc_pages(page, 0);
> + order = page_private(page);
> + nr_pages = 1 << order;
> + set_page_private(page, 0);
> + set_page_refcounted(page);
> +
> + arch_alloc_page(page, order);
> + kernel_map_pages(page, nr_pages, 1);
> + kasan_alloc_pages(page, order);
> + if (order)
> + split_page(page, order);
> +
> + for (i = 0; i < nr_pages; i++) {
> + list_add(&page->lru, &tmp_list);
> + page++;
> + }
> }
> +
> + list_splice(&tmp_list, list);
> }
>
> static inline bool migrate_async_suitable(int migratetype)
> @@ -406,12 +424,13 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
> unsigned long flags = 0;
> bool locked = false;
> unsigned long blockpfn = *start_pfn;
> + unsigned int order;
>
> cursor = pfn_to_page(blockpfn);
>
> /* Isolate free pages. */
> for (; blockpfn < end_pfn; blockpfn++, cursor++) {
> - int isolated, i;
> + int isolated;
> struct page *page = cursor;
>
> /*
> @@ -477,17 +496,17 @@ static unsigned long isolate_freepages_block(struct compact_control *cc,
> goto isolate_fail;
> }
>
> - /* Found a free page, break it into order-0 pages */
> - isolated = split_free_page(page);
> + /* Found a free page, will break it into order-0 pages */
> + order = page_order(page);
> + isolated = __isolate_free_page(page, order);
> if (!isolated)
> break;
> + set_page_private(page, order);
>
> total_isolated += isolated;
> cc->nr_freepages += isolated;
> - for (i = 0; i < isolated; i++) {
> - list_add(&page->lru, freelist);
> - page++;
> - }
> + list_add_tail(&page->lru, freelist);
> +
> if (!strict && cc->nr_migratepages <= cc->nr_freepages) {
> blockpfn += isolated;
> break;
> @@ -606,7 +625,7 @@ isolate_freepages_range(struct compact_control *cc,
> */
> }
>
> - /* split_free_page does not map the pages */
> + /* __isolate_free_page() does not map the pages */
> map_pages(&freelist);
>
> if (pfn < end_pfn) {
> @@ -1113,7 +1132,7 @@ static void isolate_freepages(struct compact_control *cc)
> }
> }
>
> - /* split_free_page does not map the pages */
> + /* __isolate_free_page() does not map the pages */
> map_pages(freelist);
>
> /*
> diff --git a/mm/page_alloc.c b/mm/page_alloc.c
> --- a/mm/page_alloc.c
> +++ b/mm/page_alloc.c
> @@ -2560,33 +2560,6 @@ int __isolate_free_page(struct page *page, unsigned int order)
> }
>
> /*
> - * Similar to split_page except the page is already free. As this is only
> - * being used for migration, the migratetype of the block also changes.
> - * As this is called with interrupts disabled, the caller is responsible
> - * for calling arch_alloc_page() and kernel_map_page() after interrupts
> - * are enabled.
> - *
> - * Note: this is probably too low level an operation for use in drivers.
> - * Please consult with lkml before using this in your driver.
> - */
> -int split_free_page(struct page *page)
> -{
> - unsigned int order;
> - int nr_pages;
> -
> - order = page_order(page);
> -
> - nr_pages = __isolate_free_page(page, order);
> - if (!nr_pages)
> - return 0;
> -
> - /* Split into individual pages */
> - set_page_refcounted(page);
> - split_page(page, order);
> - return nr_pages;
> -}
> -
> -/*
> * Update NUMA hit/miss statistics
> *
> * Must be called with interrupts disabled.
>
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