Re: [PATCH v2 1/1] mm: ALLOC_HIGHATOMIC flag allocation issue

[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

 





在 2023/11/10 1:49, Andrew Morton 写道:
On Thu,  9 Nov 2023 15:31:33 +0800 Zhiguo Jiang <justinjiang@xxxxxxxx> wrote:

Add a new bool* argument to pass return flag instead of *alloc_flags
and add the related comments.
Please retain (and update) the changelog with each version of a patch.
ok,I will supplement it if there is a later version.

For reviewers (please), here's the v1 changelog:

: In case of alloc_flags contain ALLOC_HIGHATOMIC and alloc order
: is order1/2/3/10 in rmqueue(), if pages are alloced successfully
: from pcplist cache, and move a free pageblock from the alloced
: migratetype freelist to MIGRATE_HIGHATOMIC freelist, rather than
: alloc from MIGRATE_HIGHATOMIC freelist firstly, so this will result
: in an increasing number of pages on the MIGRATE_HIGHATOMIC freelist,
: pages in other migratetype freelist are reduced and more likely to
: allocation failure.
:
: Currently the sequence of ALLOC_HIGHATOMIC allocation is:
: pcplist cache --> buddy (batch >> order) allocation migratetype
: freelist --> buddy MIGRATE_HIGHATOMIC freelist --> buddy allocation
: migratetype freelist.
:
: Due to the fact that requesting pages from the pcplist cache is faster
: than buddy, the sequence of modifying the ALLOC_HIGHATOMIC allocation is:
: pcplist --> buddy MIGRATE_HIGHATOMIC freelist --> buddy allocation
: migrate freelist.
:
: This patch can solve the allocation failure of the Non-ALLOC_HIGHATOMIC
: alloc_flag due to excessive pages reservations in MIGRATE_HIGHATOMIC
: freelists.

--- a/mm/internal.h
+++ b/mm/internal.h
@@ -905,7 +905,6 @@ unsigned int reclaim_clean_pages_from_list(struct zone *zone,
  #endif
  #define ALLOC_HIGHATOMIC	0x200 /* Allows access to MIGRATE_HIGHATOMIC */
  #define ALLOC_KSWAPD		0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
-#define ALLOC_PCPLIST		0x1000 /* Allocations from pcplist */
/* Flags that allow allocations below the min watermark. */
  #define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 67cec88164b1..3c84c3e3eeb0 100755
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2854,6 +2854,11 @@ struct page *__rmqueue_pcplist(struct zone *zone, unsigned int order,
  			int batch = nr_pcp_alloc(pcp, zone, order);
  			int alloced;
+ /*
+			 * If pcplist is empty and alloc_flags is with ALLOC_HIGHATOMIC,
+			 * it should alloc from buddy highatomic migrate freelist firstly
+			 * to ensure quick and successful allocation.
+			 */
  			if (alloc_flags & ALLOC_HIGHATOMIC)
  				goto out;
@@ -2925,8 +2930,8 @@ __no_sanitize_memory
  static inline
  struct page *rmqueue(struct zone *preferred_zone,
  			struct zone *zone, unsigned int order,
-			gfp_t gfp_flags, unsigned int *alloc_flags,
-			int migratetype)
+			gfp_t gfp_flags, unsigned int alloc_flags,
+			int migratetype, bool *highatomc_allocation)
  {
  	struct page *page;
@@ -2938,19 +2943,33 @@ struct page *rmqueue(struct zone *preferred_zone, if (likely(pcp_allowed_order(order))) {
  		page = rmqueue_pcplist(preferred_zone, zone, order,
-				       migratetype, *alloc_flags);
-		if (likely(page)) {
-			*alloc_flags |= ALLOC_PCPLIST;
+				       migratetype, alloc_flags);
+		if (likely(page))
  			goto out;
-		}
  	}
- page = rmqueue_buddy(preferred_zone, zone, order, *alloc_flags,
+	page = rmqueue_buddy(preferred_zone, zone, order, alloc_flags,
  							migratetype);
+ /*
+	 * The high-order atomic allocation pageblock reserved conditions:
+	 *
+	 * If the high-order atomic allocation page is alloced from pcplist,
+	 * the highatomic pageblock does not need to be reserved, which can
+	 * void to migrate an increasing number of pages into buddy
+	 * MIGRATE_HIGHATOMIC freelist and lead to an increasing risk of
+	 * allocation failure on other buddy migrate freelists.
+	 *
+	 * If the high-order atomic allocation page is alloced from buddy
+	 * highatomic migrate freelist, regardless of whether the allocation
+	 * is successful or not, the highatomic pageblock can try to be
+	 * reserved.
+	 */
+	if (unlikely(alloc_flags & ALLOC_HIGHATOMIC))
+		*highatomc_allocation = true;
  out:
  	/* Separate test+clear to avoid unnecessary atomics */
-	if ((*alloc_flags & ALLOC_KSWAPD) &&
+	if ((alloc_flags & ALLOC_KSWAPD) &&
  	    unlikely(test_bit(ZONE_BOOSTED_WATERMARK, &zone->flags))) {
  		clear_bit(ZONE_BOOSTED_WATERMARK, &zone->flags);
  		wakeup_kswapd(zone, 0, 0, zone_idx(zone));
@@ -3218,6 +3237,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
  	struct pglist_data *last_pgdat = NULL;
  	bool last_pgdat_dirty_ok = false;
  	bool no_fallback;
+	bool highatomc_allocation = false;
retry:
  	/*
@@ -3349,7 +3369,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
try_this_zone:
  		page = rmqueue(ac->preferred_zoneref->zone, zone, order,
-				gfp_mask, &alloc_flags, ac->migratetype);
+				gfp_mask, alloc_flags, ac->migratetype, &highatomc_allocation);
  		if (page) {
  			prep_new_page(page, order, gfp_mask, alloc_flags);
@@ -3357,8 +3377,7 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
  			 * If this is a high-order atomic allocation then check
  			 * if the pageblock should be reserved for the future
  			 */
-			if (unlikely(alloc_flags & ALLOC_HIGHATOMIC) &&
-				unlikely(!(alloc_flags & ALLOC_PCPLIST)))
+			if (unlikely(highatomc_allocation))
  				reserve_highatomic_pageblock(page, zone);
return page;
--
2.39.0





[Index of Archives]     [Linux ARM Kernel]     [Linux ARM]     [Linux Omap]     [Fedora ARM]     [IETF Annouce]     [Bugtraq]     [Linux OMAP]     [Linux MIPS]     [eCos]     [Asterisk Internet PBX]     [Linux API]

  Powered by Linux