For single threaded workloads, we can avoid flushing
and iterating through the entire list of tasks, making
the whole function a lot faster, requiring only a single
atomic read for the mm_users.
Suggested-by: Oleg Nesterov <oleg@xxxxxxxxxx>
Signed-off-by: Davidlohr Bueso <davidlohr@xxxxxx>
---
mm/vmacache.c | 10 ++++++++++
1 file changed, 10 insertions(+)
diff --git a/mm/vmacache.c b/mm/vmacache.c
index e167da2..61c38ae 100644
--- a/mm/vmacache.c
+++ b/mm/vmacache.c
@@ -17,6 +17,16 @@ void vmacache_flush_all(struct mm_struct *mm)
{
struct task_struct *g, *p;
+ /*
+ * Single threaded tasks need not iterate the entire
+ * list of process. We can avoid the flushing as well
+ * since the mm's seqnum was increased and don't have
+ * to worry about other threads' seqnum. Current's
+ * flush will occur upon the next lookup.
+ */
+ if (atomic_read(&mm->mm_users) == 1)
+ return;
+
rcu_read_lock();
for_each_process_thread(g, p) {
/*
--
1.8.1.4
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