I sent this patch back on 9/19 and it never went anywhere. I'm sending
it again, against the lastest unstable.
-- Steve
==== Originally sent 9/19/2006 ====
If someone turns on verbose and/or debug the hypervisor slams the serial
pretty badly when starting a FV domain. So I pulled the
printk_ratelimit from Linux and put it into the hypervisor. Right now
the only user of it is the MEM_LOG in arch/x86/mm.c which can really
spit out a lot.
Since printk_ratelimit is very helpful in the Linux kernel, I can see it
being also used in HV. I changed it slightly from Linux to match the
naming convention in Xen. Since printk is defined to printf, I declared
the function printf_ratelimit and made a define of printk_ratelimit to
just be a clone of printf_ratelimit.
-- Steve
Signed-off-by: Steven Rostedt <srostedt@xxxxxxxxxx>
diff -r f0302ed1ac62 xen/arch/x86/mm.c
--- a/xen/arch/x86/mm.c Mon Oct 02 11:47:55 2006 -0400
+++ b/xen/arch/x86/mm.c Mon Oct 02 11:48:22 2006 -0400
@@ -109,9 +109,13 @@
#include <public/memory.h>
#ifdef VERBOSE
-#define MEM_LOG(_f, _a...) \
- printk("DOM%u: (file=mm.c, line=%d) " _f "\n", \
- current->domain->domain_id , __LINE__ , ## _a )
+#define MEM_LOG(_f, _a...) \
+ do { \
+ if (printk_ratelimit()) { \
+ printk("DOM%u: (file=mm.c, line=%d) " _f "\n", \
+ current->domain->domain_id , __LINE__ , ## _a ); \
+ } \
+ } while (0)
#else
#define MEM_LOG(_f, _a...) ((void)0)
#endif
diff -r f0302ed1ac62 xen/drivers/char/console.c
--- a/xen/drivers/char/console.c Mon Oct 02 11:47:55 2006 -0400
+++ b/xen/drivers/char/console.c Mon Oct 02 11:48:22 2006 -0400
@@ -4,6 +4,10 @@
* Emergency console I/O for Xen and the domain-0 guest OS.
*
* Copyright (c) 2002-2004, K A Fraser.
+ *
+ * Added printf_ratelimit
+ * Taken from Linux - Author: Andi Kleen (net_ratelimit)
+ * Ported to Xen - Steven Rostedt - Red Hat
*/
#include <stdarg.h>
@@ -465,6 +469,52 @@ int console_getc(void)
return serial_getc(sercon_handle);
}
+/*
+ * printk rate limiting, lifted from Linux.
+ *
+ * This enforces a rate limit: not more than one kernel message
+ * every printf_ratelimit_jiffies.
+ */
+int __printf_ratelimit(int ratelimit_jiffies, int ratelimit_burst)
+{
+ static DEFINE_SPINLOCK(ratelimit_lock);
+ static unsigned long toks = 10 * 5 * HZ;
+ static unsigned long last_msg;
+ static int missed;
+ unsigned long flags;
+ unsigned long now = jiffies;
+
+ spin_lock_irqsave(&ratelimit_lock, flags);
+ toks += now - last_msg;
+ last_msg = now;
+ if (toks > (ratelimit_burst * ratelimit_jiffies))
+ toks = ratelimit_burst * ratelimit_jiffies;
+ if (toks >= ratelimit_jiffies) {
+ int lost = missed;
+
+ missed = 0;
+ toks -= ratelimit_jiffies;
+ spin_unlock_irqrestore(&ratelimit_lock, flags);
+ if (lost)
+ printk("printk: %d messages suppressed.\n", lost);
+ return 1;
+ }
+ missed++;
+ spin_unlock_irqrestore(&ratelimit_lock, flags);
+ return 0;
+}
+
+/* minimum time in jiffies between messages */
+int printf_ratelimit_jiffies = 5 * HZ;
+
+/* number of messages we send before ratelimiting */
+int printf_ratelimit_burst = 10;
+
+int printf_ratelimit(void)
+{
+ return __printf_ratelimit(printf_ratelimit_jiffies,
+ printf_ratelimit_burst);
+}
/*
* **************************************************************
diff -r f0302ed1ac62 xen/include/xen/lib.h
--- a/xen/include/xen/lib.h Mon Oct 02 11:47:55 2006 -0400
+++ b/xen/include/xen/lib.h Mon Oct 02 11:48:22 2006 -0400
@@ -52,8 +52,11 @@ extern void debugtrace_printk(const char
/* Allows us to use '%p' as general-purpose machine-word format char. */
#define _p(_x) ((void *)(unsigned long)(_x))
#define printk(_f , _a...) printf( _f , ## _a )
+#define printk_ratelimit() printf_ratelimit()
extern void printf(const char *format, ...)
__attribute__ ((format (printf, 1, 2)));
+extern int __printf_ratelimit(int ratelimit_jiffies, int ratelimit_burst);
+extern int printf_ratelimit(void);
extern void panic(const char *format, ...)
__attribute__ ((format (printf, 1, 2)));
extern long vm_assist(struct domain *, unsigned int, unsigned int);
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