linux-kernel - [PATCH] mm/page_alloc: Skip setting nodemask when we are in interrupt

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Message-Id: <20200603155124.33981-1-songmuchun@bytedance.com>
Date:   Wed,  3 Jun 2020 23:51:24 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     akpm@...ux-foundation.org
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>
Subject: [PATCH] mm/page_alloc: Skip setting nodemask when we are in interrupt

When we are in the interrupt context, it is irrelevant to the
current task context. If we use current task's mems_allowed, we
can fair to alloc pages in the fast path and fall back to slow
path memory allocation when the current node(which is the current
task mems_allowed) does not have enough memory to allocate. In
this case, it slows down the memory allocation speed of interrupt
context. So we can skip setting the nodemask to allow any node
to allocate memory, so that fast path allocation can success.

Signed-off-by: Muchun Song <songmuchun@...edance.com>
---
 mm/page_alloc.c | 8 +++++---
 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index b48336e20bdcd..a6c36cd557d1d 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -4726,10 +4726,12 @@ static inline bool prepare_alloc_pages(gfp_t gfp_mask, unsigned int order,

 	if (cpusets_enabled()) {
 		*alloc_mask |= __GFP_HARDWALL;
-		if (!ac->nodemask)
-			ac->nodemask = &cpuset_current_mems_allowed;
-		else
+		if (!ac->nodemask) {
+			if (!in_interrupt())
+				ac->nodemask = &cpuset_current_mems_allowed;
+		} else {
 			*alloc_flags |= ALLOC_CPUSET;
+		}
 	}

 	fs_reclaim_acquire(gfp_mask);
-- 
2.11.0