The patch titled
Subject: mm/page_alloc: give GFP_ATOMIC and non-blocking allocations access to reserves
has been added to the -mm mm-unstable branch. Its filename is
mm-page_alloc-give-gfp_atomic-and-non-blocking-allocations-access-to-reserves.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-give-gfp_atomic-and-non-blocking-allocations-access-to-reserves.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Subject: mm/page_alloc: give GFP_ATOMIC and non-blocking allocations access to reserves
Date: Mon, 9 Jan 2023 15:16:30 +0000
Explicit GFP_ATOMIC allocations get flagged ALLOC_HARDER which is a bit
vague. In preparation for removing __GFP_ATOMIC, give GFP_ATOMIC and
other non-blocking allocation requests equal access to reserve. Rename
ALLOC_HARDER to ALLOC_NON_BLOCK to make it more clear what the flag means.
Link: https://lkml.kernel.org/r/20230109151631.24923-7-mgorman@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: NeilBrown <neilb@xxxxxxx>
Cc: Thierry Reding <thierry.reding@xxxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/internal.h | 7 +++++--
mm/page_alloc.c | 23 +++++++++++++----------
2 files changed, 18 insertions(+), 12 deletions(-)
--- a/mm/internal.h~mm-page_alloc-give-gfp_atomic-and-non-blocking-allocations-access-to-reserves
+++ a/mm/internal.h
@@ -760,7 +760,10 @@ unsigned int reclaim_clean_pages_from_li
#define ALLOC_OOM ALLOC_NO_WATERMARKS
#endif
-#define ALLOC_HARDER 0x10 /* try to alloc harder */
+#define ALLOC_NON_BLOCK 0x10 /* Caller cannot block. Allow access
+ * to 25% of the min watermark or
+ * 62.5% if __GFP_HIGH is set.
+ */
#define ALLOC_MIN_RESERVE 0x20 /* __GFP_HIGH set. Allow access to 50%
* of the min watermark.
*/
@@ -775,7 +778,7 @@ unsigned int reclaim_clean_pages_from_li
#define ALLOC_KSWAPD 0x800 /* allow waking of kswapd, __GFP_KSWAPD_RECLAIM set */
/* Flags that allow allocations below the min watermark. */
-#define ALLOC_RESERVES (ALLOC_HARDER|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
+#define ALLOC_RESERVES (ALLOC_NON_BLOCK|ALLOC_MIN_RESERVE|ALLOC_HIGHATOMIC|ALLOC_OOM)
enum ttu_flags;
struct tlbflush_unmap_batch;
--- a/mm/page_alloc.c~mm-page_alloc-give-gfp_atomic-and-non-blocking-allocations-access-to-reserves
+++ a/mm/page_alloc.c
@@ -4014,7 +4014,7 @@ bool __zone_watermark_ok(struct zone *z,
* if it cannot get memory quickly, particularly if it's
* also __GFP_HIGH.
*/
- if (alloc_flags & ALLOC_HARDER)
+ if (alloc_flags & ALLOC_NON_BLOCK)
min -= min / 4;
/*
@@ -4866,28 +4866,30 @@ gfp_to_alloc_flags(gfp_t gfp_mask, unsig
* The caller may dip into page reserves a bit more if the caller
* cannot run direct reclaim, or if the caller has realtime scheduling
* policy or is asking for __GFP_HIGH memory. GFP_ATOMIC requests will
- * set both ALLOC_HARDER (__GFP_ATOMIC) and ALLOC_MIN_RESERVE(__GFP_HIGH).
+ * set both ALLOC_NON_BLOCK and ALLOC_MIN_RESERVE(__GFP_HIGH).
*/
alloc_flags |= (__force int)
(gfp_mask & (__GFP_HIGH | __GFP_KSWAPD_RECLAIM));
- if (gfp_mask & __GFP_ATOMIC) {
+ if (!(gfp_mask & __GFP_DIRECT_RECLAIM)) {
/*
* Not worth trying to allocate harder for __GFP_NOMEMALLOC even
* if it can't schedule.
*/
if (!(gfp_mask & __GFP_NOMEMALLOC)) {
- alloc_flags |= ALLOC_HARDER;
+ alloc_flags |= ALLOC_NON_BLOCK;
if (order > 0)
alloc_flags |= ALLOC_HIGHATOMIC;
}
/*
- * Ignore cpuset mems for GFP_ATOMIC rather than fail, see the
- * comment for __cpuset_node_allowed().
+ * Ignore cpuset mems for non-blocking __GFP_HIGH (probably
+ * GFP_ATOMIC) rather than fail, see the comment for
+ * __cpuset_node_allowed().
*/
- alloc_flags &= ~ALLOC_CPUSET;
+ if (alloc_flags & ALLOC_MIN_RESERVE)
+ alloc_flags &= ~ALLOC_CPUSET;
} else if (unlikely(rt_task(current)) && in_task())
alloc_flags |= ALLOC_MIN_RESERVE;
@@ -5319,11 +5321,12 @@ nopage:
/*
* Help non-failing allocations by giving them access to memory
- * reserves but do not use ALLOC_NO_WATERMARKS because this
+ * reserves normally used for high priority non-blocking
+ * allocations but do not use ALLOC_NO_WATERMARKS because this
* could deplete whole memory reserves which would just make
- * the situation worse
+ * the situation worse.
*/
- page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_MIN_RESERVE|ALLOC_HARDER, ac);
+ page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_MIN_RESERVE|ALLOC_NON_BLOCK, ac);
if (page)
goto got_pg;
_
Patches currently in -mm which might be from mgorman@xxxxxxxxxxxxxxxxxxx are
mm-page_alloc-rename-alloc_high-to-alloc_min_reserve.patch
mm-page_alloc-treat-rt-tasks-similar-to-__gfp_high.patch
mm-page_alloc-explicitly-record-high-order-atomic-allocations-in-alloc_flags.patch
mm-page_alloc-explicitly-define-what-alloc-flags-deplete-min-reserves.patch
mm-page_allocc-allow-__gfp_nofail-requests-deeper-access-to-reserves.patch
mm-page_alloc-give-gfp_atomic-and-non-blocking-allocations-access-to-reserves.patch
