Re: [profile] amortize atomic hit count increments

[William Lee Irwin III <wli@holomorphy.com>]

On Tue, Sep 14, 2004 at 12:00:30PM -0700, William Lee Irwin III wrote:
>>> Goddamn fscking short-format VHPT crap. Rusty, how the hell do I
>>> hotplug-ize this?

On Tue, Sep 14, 2004 at 01:02:20PM -0700, William Lee Irwin III wrote:
>> Okay, here's an attempt to hotplug-ize it. I have no clue whether this
>> actually works, compiles, or follows whatever rules there are about
>> dynamically allocated data referenced by per_cpu areas.

On Tue, Sep 14, 2004 at 01:04:53PM -0700, William Lee Irwin III wrote:
> Take 2: actually register the notifier I wrote.

As pointed out by John Hawkes, I forgot to flush the pending hits at
the time of profile buffer reset. The following patch, atop the cpu
hotplug notifier bits, does so.

Index: mm5-2.6.9-rc1/kernel/profile.c
===================================================================
--- mm5-2.6.9-rc1.orig/kernel/profile.c	2004-09-14 12:56:33.871160032 -0700
+++ mm5-2.6.9-rc1/kernel/profile.c	2004-09-14 13:43:55.826117208 -0700
@@ -37,6 +37,7 @@
 #ifdef CONFIG_SMP
 static DEFINE_PER_CPU(struct profile_hit *[2], cpu_profile_hits);
 static DEFINE_PER_CPU(int, cpu_profile_flip);
+static DECLARE_MUTEX(profile_flip_mutex);
 #endif /* CONFIG_SMP */
 
 static int __init profile_setup(char * str)
@@ -242,7 +243,6 @@
 
 static void profile_flip_buffers(void)
 {
-	static DECLARE_MUTEX(profile_flip_mutex);
 	int i, j, cpu;
 
 	down(&profile_flip_mutex);
@@ -261,6 +261,22 @@
 	up(&profile_flip_mutex);
 }
 
+static void profile_discard_flip_buffers(void)
+{
+	static DECLARE_MUTEX(profile_flip_mutex);
+	int i, cpu;
+
+	down(&profile_flip_mutex);
+	i = per_cpu(cpu_profile_flip, get_cpu());
+	put_cpu();
+	on_each_cpu(__profile_flip_buffers, NULL, 0, 1);
+	for_each_online_cpu(cpu) {
+		struct profile_hit *hits = per_cpu(cpu_profile_hits, cpu)[i];
+		memset(hits, 0, NR_PROFILE_HIT*sizeof(struct profile_hit));
+	}
+	up(&profile_flip_mutex);
+}
+
 void profile_hit(int type, void *__pc)
 {
 	unsigned long primary, secondary, flags, pc = (unsigned long)__pc;
@@ -338,6 +354,7 @@
 #endif /* CONFIG_HOTPLUG_CPU */
 #else /* !CONFIG_SMP */
 #define profile_flip_buffers()		do { } while (0)
+#define profile_discard_flip_buffers()	do { } while (0)
 
 void profile_hit(int type, void *__pc)
 {
@@ -456,7 +473,7 @@
 			return -EINVAL;
 	}
 #endif
-
+	profile_discard_flip_buffers();
 	memset(prof_buffer, 0, prof_len * sizeof(atomic_t));
 	return count;
 }