The patch titled
Subject: mm: optimization on page allocation when CMA enabled
has been added to the -mm mm-unstable branch. Its filename is
mm-optimization-on-page-allocation-when-cma-enabled.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-optimization-on-page-allocation-when-cma-enabled.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
Before you just go and hit "reply", please:
a) Consider who else should be cc'ed
b) Prefer to cc a suitable mailing list as well
c) Ideally: find the original patch on the mailing list and do a
reply-to-all to that, adding suitable additional cc's
*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next via the mm-everything
branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
and is updated there every 2-3 working days
------------------------------------------------------
From: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
Subject: mm: optimization on page allocation when CMA enabled
Date: Thu, 11 May 2023 13:22:30 +0800
Let us look at the timeline of scenarios below with WMARK_LOW=25MB
WMARK_MIN=5MB (managed pages 1.9GB). We can find that CMA begin to be
used until 'C' under the method of 'fixed 2 times of free cma over free
pages' which could have the scenario 'A' and 'B' into a fault state, that
is, free UNMOVABLE & RECLAIMABLE pages is lower than corresponding
watermark without reclaiming which should be deemed as against current
memory policy. This commit try to solve this by checking
zone_watermark_ok again with removing CMA pages which could lead to a
proper time point of CMA's utilization.
-- Free_pages
|
|
-- WMARK_LOW
|
-- Free_CMA
|
|
--
Free_CMA/Free_pages(MB) A(12/30) --> B(12/25) --> C(12/20)
fixed 1/2 ratio N N Y
this commit Y Y Y
Link: https://lkml.kernel.org/r/1683782550-25799-1-git-send-email-zhaoyang.huang@xxxxxxxxxx
Signed-off-by: Zhaoyang Huang <zhaoyang.huang@xxxxxxxxxx>
Cc: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>
Cc: ke.wang <ke.wang@xxxxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Roman Gushchin <roman.gushchin@xxxxxxxxx>
Cc: Zhaoyang Huang <huangzhaoyang@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 44 ++++++++++++++++++++++++++++++++++++++++----
1 file changed, 40 insertions(+), 4 deletions(-)
--- a/mm/page_alloc.c~mm-optimization-on-page-allocation-when-cma-enabled
+++ a/mm/page_alloc.c
@@ -2275,6 +2275,43 @@ do_steal:
}
+#ifdef CONFIG_CMA
+/*
+ * GFP_MOVABLE allocation could drain UNMOVABLE & RECLAIMABLE page blocks via
+ * the help of CMA which makes GFP_KERNEL failed. Checking if zone_watermark_ok
+ * again without ALLOC_CMA to see if to use CMA first.
+ */
+static bool use_cma_first(struct zone *zone, unsigned int order, unsigned int alloc_flags)
+{
+ unsigned long watermark;
+ bool cma_first = false;
+
+ watermark = wmark_pages(zone, alloc_flags & ALLOC_WMARK_MASK);
+ /* check if GFP_MOVABLE pass previous zone_watermark_ok via the help of CMA */
+ if (zone_watermark_ok(zone, order, watermark, 0, alloc_flags & (~ALLOC_CMA))) {
+ /*
+ * Balance movable allocations between regular and CMA areas by
+ * allocating from CMA when over half of the zone's free memory
+ * is in the CMA area.
+ */
+ cma_first = (zone_page_state(zone, NR_FREE_CMA_PAGES) >
+ zone_page_state(zone, NR_FREE_PAGES) / 2);
+ } else {
+ /*
+ * watermark failed means UNMOVABLE & RECLAIMBLE is not enough
+ * now, we should use cma first to keep them stay around the
+ * corresponding watermark
+ */
+ cma_first = true;
+ }
+ return cma_first;
+}
+#else
+static bool use_cma_first(struct zone *zone, unsigned int order, unsigned int alloc_flags)
+{
+ return false;
+}
+#endif
/*
* Do the hard work of removing an element from the buddy allocator.
* Call me with the zone->lock already held.
@@ -2288,12 +2325,11 @@ __rmqueue(struct zone *zone, unsigned in
if (IS_ENABLED(CONFIG_CMA)) {
/*
* Balance movable allocations between regular and CMA areas by
- * allocating from CMA when over half of the zone's free memory
- * is in the CMA area.
+ * allocating from CMA base on judging zone_watermark_ok again
+ * to see if the latest check got pass via the help of CMA
*/
if (alloc_flags & ALLOC_CMA &&
- zone_page_state(zone, NR_FREE_CMA_PAGES) >
- zone_page_state(zone, NR_FREE_PAGES) / 2) {
+ use_cma_first(zone, order, alloc_flags)) {
page = __rmqueue_cma_fallback(zone, order);
if (page)
return page;
_
Patches currently in -mm which might be from zhaoyang.huang@xxxxxxxxxx are
mm-optimization-on-page-allocation-when-cma-enabled.patch
