This patch adds the feature of irq ratelimit. It temporarily masks
the interrupt (guest) if too many irqs are observed in a short
period (irq storm), to ensure responsiveness of Xen and other guests.
As for now, the threshold can be adjusted at boot time using command-
line option irq_ratelimit=.
Signed-off-by: Qing He <qing.he@xxxxxxxxx>
---
arch/x86/irq.c | 64 ++++++++++++++++++++++++++++++++++++++++++++++++++++++
include/xen/irq.h | 6 +++++
2 files changed, 70 insertions(+)
diff -r 8f81bdd57afe xen/arch/x86/irq.c
--- a/xen/arch/x86/irq.c Thu Sep 03 09:51:37 2009 +0100
+++ b/xen/arch/x86/irq.c Tue Sep 15 18:16:38 2009 +0800
@@ -54,6 +54,14 @@ DEFINE_PER_CPU(vector_irq_t, vector_irq)
};
DEFINE_PER_CPU(struct cpu_user_regs *, __irq_regs);
+
+static LIST_HEAD(irq_ratelimit_list);
+static DEFINE_SPINLOCK(irq_ratelimit_lock);
+static struct timer irq_ratelimit_timer;
+
+/* irq_ratelimit: the max irq rate allowed in every 10ms, set 0 to disable */
+unsigned int __read_mostly irq_ratelimit_threshold = 10000;
+integer_param("irq_ratelimit", irq_ratelimit_threshold);
/* Must be called when irq disabled */
void lock_vector_lock(void)
@@ -241,6 +249,10 @@ static void init_one_irq_desc(struct irq
desc->msi_desc = NULL;
spin_lock_init(&desc->lock);
cpus_setall(desc->affinity);
+
+ desc->rl_quantum_start = NOW();
+ desc->rl_cnt = 0;
+ INIT_LIST_HEAD(&desc->rl_link);
}
static void init_one_irq_status(int irq)
@@ -469,6 +481,29 @@ asmlinkage void do_IRQ(struct cpu_user_r
if ( likely(desc->status & IRQ_GUEST) )
{
+ s_time_t now = NOW();
+ if ( now > (desc->rl_quantum_start + MILLISECS(10)) ) {
+ desc->rl_cnt = 0;
+ desc->rl_quantum_start = now;
+ }
+ if ( unlikely(desc->rl_cnt++ >= irq_ratelimit_threshold) ) {
+ desc->handler->disable(irq);
+ /*
+ * If handler->disable doesn't actually mask the interrupt,
+ * a disabled irq still can fire. This check also avoids
+ * possible deadlocks if ratelimit_timer_fn runs at the
+ * same time.
+ */
+ if ( likely(list_empty(&desc->rl_link)) ) {
+ spin_lock(&irq_ratelimit_lock);
+ if ( list_empty(&irq_ratelimit_list) )
+ set_timer(&irq_ratelimit_timer, now + MILLISECS(10));
+ list_add(&desc->rl_link, &irq_ratelimit_list);
+ spin_unlock(&irq_ratelimit_lock);
+ }
+ goto out;
+ }
+
irq_enter();
tsc_in = tb_init_done ? get_cycles() : 0;
__do_IRQ_guest(irq);
@@ -511,6 +546,35 @@ asmlinkage void do_IRQ(struct cpu_user_r
spin_unlock(&desc->lock);
set_irq_regs(old_regs);
}
+
+static void irq_ratelimit_timer_fn(void *data)
+{
+ struct irq_desc *desc, *tmp;
+ unsigned long flags;
+
+ spin_lock_irqsave(&irq_ratelimit_lock, flags);
+
+ list_for_each_entry_safe(desc, tmp, &irq_ratelimit_list, rl_link) {
+ spin_lock(&desc->lock);
+ desc->handler->enable(desc->irq);
+ list_del(&desc->rl_link);
+ INIT_LIST_HEAD(&desc->rl_link);
+ spin_unlock(&desc->lock);
+ }
+
+ spin_unlock_irqrestore(&irq_ratelimit_lock, flags);
+}
+
+static int __init irq_ratelimit_init(void)
+{
+ init_timer(&irq_ratelimit_timer, irq_ratelimit_timer_fn, NULL, 0);
+
+ if (irq_ratelimit_threshold == 0)
+ irq_ratelimit_threshold = ~0U;
+
+ return 0;
+}
+__initcall(irq_ratelimit_init);
int request_irq(unsigned int irq,
void (*handler)(int, void *, struct cpu_user_regs *),
diff -r 8f81bdd57afe xen/include/xen/irq.h
--- a/xen/include/xen/irq.h Thu Sep 03 09:51:37 2009 +0100
+++ b/xen/include/xen/irq.h Tue Sep 15 18:16:38 2009 +0800
@@ -4,6 +4,7 @@
#include <xen/config.h>
#include <xen/cpumask.h>
#include <xen/spinlock.h>
+#include <xen/time.h>
#include <asm/regs.h>
#include <asm/hardirq.h>
@@ -74,6 +75,11 @@ typedef struct irq_desc {
int irq;
spinlock_t lock;
cpumask_t affinity;
+
+ /* irq ratelimit */
+ s_time_t rl_quantum_start;
+ unsigned int rl_cnt;
+ struct list_head rl_link;
} __cacheline_aligned irq_desc_t;
#if defined(__ia64__)
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