From: jun qian <qianjun.ker...@gmail.com>
When get the pending softirqs, it need to process all the pending
softirqs in the while loop. If the processing time of each pending
softirq is need more than 2 msec in this loop, or one of the softirq
will running a long time, according to the original code logic, it
will process all the pending softirqs without wakeuping ksoftirqd,
which will cause a relatively large scheduling delay on the
corresponding CPU, which we do not wish to see. The patch will check
the total time to process pending softirq, if the time exceeds 2 ms
we need to wakeup the ksofirqd to aviod large sched delay.
Signed-off-by: jun qian <qianjun.ker...@gmail.com>
---
kernel/softirq.c | 20 +++++++++++++++++---
1 file changed, 17 insertions(+), 3 deletions(-)
diff --git a/kernel/softirq.c b/kernel/softirq.c
index c4201b7f..f8e5be9 100644
--- a/kernel/softirq.c
+++ b/kernel/softirq.c
@@ -210,7 +210,7 @@ void __local_bh_enable_ip(unsigned long ip, unsigned int
cnt)
* we want to handle softirqs as soon as possible, but they
* should not be able to lock up the box.
*/
-#define MAX_SOFTIRQ_TIME msecs_to_jiffies(2)
+#define MAX_SOFTIRQ_TIME 2000 /* In microseconds */
#define MAX_SOFTIRQ_RESTART 10
#ifdef CONFIG_TRACE_IRQFLAGS
@@ -248,7 +248,8 @@ static inline void lockdep_softirq_end(bool in_hardirq) { }
asmlinkage __visible void __softirq_entry __do_softirq(void)
{
- unsigned long end = jiffies + MAX_SOFTIRQ_TIME;
+ ktime_t end, start;
+ s64 delta;
unsigned long old_flags = current->flags;
int max_restart = MAX_SOFTIRQ_RESTART;
struct softirq_action *h;
@@ -256,6 +257,8 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
__u32 pending;
int softirq_bit;
+ start = ktime_get();
+
/*
* Mask out PF_MEMALLOC as the current task context is borrowed for the
* softirq. A softirq handled, such as network RX, might set PF_MEMALLOC
@@ -299,6 +302,15 @@ asmlinkage __visible void __softirq_entry
__do_softirq(void)
}
h++;
pending >>= softirq_bit;
+
+ end = ktime_get();
+ delta = ktime_to_us(end - start);
+ /*
+ * the softirq's action has been running for too much time
+ * so it may need to wakeup the ksoftirqd
+ */
+ if (delta > MAX_SOFTIRQ_TIME && need_resched())
+ break;
}
if (__this_cpu_read(ksoftirqd) == current)
@@ -307,7 +319,9 @@ asmlinkage __visible void __softirq_entry __do_softirq(void)
pending = local_softirq_pending();
if (pending) {
- if (time_before(jiffies, end) && !need_resched() &&
+ end = ktime_get();
+ delta = ktime_to_us(end - start);
+ if (delta < MAX_SOFTIRQ_TIME && !need_resched() &&
--max_restart)
goto restart;
--
1.8.3.1
