[patch 154/163] mm/page_alloc.c: skip setting nodemask when we are in interrupt

Andrew Morton
2020-08-07T06:26:14Z

From: Muchun Song <songmuchun@bytedance.com>
Subject: mm/page_alloc.c: 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 be 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.

Link: http://lkml.kernel.org/r/20200706025921.53683-1-songmuchun@bytedance.com
Signed-off-by: Muchun Song <songmuchun@bytedance.com>
Reviewed-by: Pekka Enberg <penberg@kernel.org>
Cc: David Hildenbrand <david@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

mm/page_alloc.c | 6 +++++-
1 file changed, 5 insertions(+), 1 deletion(-)

--- a/mm/page_alloc.c~mm-page_alloc-skip-setting-nodemask-when-we-are-in-interrupt
+++ a/mm/page_alloc.c
@@ -4788,7 +4788,11 @@ static inline bool prepare_alloc_pages(g

if (cpusets_enabled()) {
*alloc_mask |= __GFP_HARDWALL;
- if (!ac->nodemask)
+ /*
+ * When we are in the interrupt context, it is irrelevant
+ * to the current task context. It means that any node ok.
+ */
+ if (!in_interrupt() && !ac->nodemask)
ac->nodemask = &cpuset_current_mems_allowed;
else
*alloc_flags |= ALLOC_CPUSET;
_