sched: avoid migrating when softint on tgt cpu should be short
The scheduling change (bug 31501544) to avoid putting RT threads on cores that
are handling softint's was catching cases where there was no reason
to believe the softint would take a long time, resulting in unnecessary
migration overhead. This patch reduces the migration to cases where
the core has a softint that is actually likely to take a long time,
as opposed to the RCU, SCHED, and TIMER softints that are rather quick.
Bug: 31752786
Change-Id: Ib4e179f1e15c736b2fdba31070494e357e9fbbe2
Git-commit: ce05770bd37b8065b61ef650108ecef2b97b148b
Git-repo: https://android.googlesource.com/kernel/msm
[pkondeti@codeaurora.org: resolved minor merge conflicts]
Signed-off-by: Pavankumar Kondeti <pkondeti@codeaurora.org>
diff --git a/kernel/softirq.c b/kernel/softirq.c
index 744fa61..bde8e33 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -57,6 +57,13 @@
DEFINE_PER_CPU(struct task_struct *, ksoftirqd);
+/*
+ * active_softirqs -- per cpu, a mask of softirqs that are being handled,
+ * with the expectation that approximate answers are acceptable and therefore
+ * no synchronization.
+ */
+DEFINE_PER_CPU(__u32, active_softirqs);
+
const char * const softirq_to_name[NR_SOFTIRQS] = {
"HI", "TIMER", "NET_TX", "NET_RX", "BLOCK", "IRQ_POLL",
"TASKLET", "SCHED", "HRTIMER", "RCU"
@@ -264,6 +271,7 @@
restart:
/* Reset the pending bitmask before enabling irqs */
set_softirq_pending(0);
+ __this_cpu_write(active_softirqs, pending);
local_irq_enable();
@@ -293,6 +301,7 @@
pending >>= softirq_bit;
}
+ __this_cpu_write(active_softirqs, 0);
rcu_bh_qs();
local_irq_disable();