Re: [patch] mm, compaction: abort free scanner if split fails
From: Vlastimil Babka
Date: Thu Jun 23 2016 - 07:22:07 EST
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@xxxxxxx>
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@xxxxxxx>
Acked-by: Vlastimil Babka <vbabka@xxxxxxx>
---
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.