From: "David S. Miller" <davem@redhat.com>
Stick this into -mm and see if people bark. :-)
It's from Ingo Molnar, softirq kicks in way too early.
We can probably sysctl this thing, that way everyone gets
what they want probably...
kernel/softirq.c | 18 +++++++++++++-----
1 files changed, 13 insertions(+), 5 deletions(-)
diff -puN kernel/softirq.c~delay-ksoftirqd-fallback kernel/softirq.c
--- 25/kernel/softirq.c~delay-ksoftirqd-fallback 2003-07-03 22:08:02.000000000 -0700
+++ 25-akpm/kernel/softirq.c 2003-07-03 22:08:02.000000000 -0700
@@ -59,11 +59,22 @@ static inline void wakeup_softirqd(void)
wake_up_process(tsk);
}
+/*
+ * We restart softirq processing MAX_SOFTIRQ_RESTART times,
+ * and we fall back to softirqd after that.
+ *
+ * This number has been established via experimentation.
+ * The two things to balance is latency against fairness -
+ * we want to handle softirqs as soon as possible, but they
+ * should not be able to lock up the box.
+ */
+#define MAX_SOFTIRQ_RESTART 10
+
asmlinkage void do_softirq(void)
{
+ int max_restart = MAX_SOFTIRQ_RESTART;
__u32 pending;
unsigned long flags;
- __u32 mask;
if (in_interrupt())
return;
@@ -75,7 +86,6 @@ asmlinkage void do_softirq(void)
if (pending) {
struct softirq_action *h;
- mask = ~pending;
local_bh_disable();
restart:
/* Reset the pending bitmask before enabling irqs */
@@ -95,10 +105,8 @@ restart:
local_irq_disable();
pending = local_softirq_pending();
- if (pending & mask) {
- mask &= ~pending;
+ if (pending && --max_restart)
goto restart;
- }
if (pending)
wakeup_softirqd();
__local_bh_enable();
_