[patch] fix oprofile SMP ...

[patch] fix oprofile SMP ...

[Davide Libenzi]

This fixed oprofile being broken on x86-64 SMP. The current reservation 
runs on all CPUs, but the ones following the first, will fail since the 
reservation bitmap has an 1 in the MSR entry.
The reservation code should really run once, and their addresses used on 
other CPUs. There are other solutions to this, but this is the simplest 
and shorter one that came in my mind. Tested in my dual Opteron 252, and 
working fine here.
Andi, if you don't like both Ben and my patch, would you mind fixing 
oprofile yourself in some way?



Signed-off-by: Davide Libenzi <davidel@xmailserver.org>



- Davide



Index: linux-2.6.22-rc1-git6.oprof/arch/i386/oprofile/nmi_int.c
===================================================================
--- linux-2.6.22-rc1-git6.oprof.orig/arch/i386/oprofile/nmi_int.c	2007-05-17 18:32:48.000000000 -0700
+++ linux-2.6.22-rc1-git6.oprof/arch/i386/oprofile/nmi_int.c	2007-05-17 18:51:28.000000000 -0700
@@ -130,8 +130,19 @@
 static void nmi_save_registers(void * dummy)
 {
 	int cpu = smp_processor_id();
-	struct op_msrs * msrs = &cpu_msrs[cpu];
-	model->fill_in_addresses(msrs);
+	struct op_msrs *msrs = &cpu_msrs[cpu];
+
+	/*
+	 * Use the CPU#0 already allocated addresses as reference.
+	 */
+	if (cpu != 0) {
+		const struct op_msrs *rmsrs = &cpu_msrs[0];
+
+		memcpy(msrs->counters, rmsrs->counters,
+		       model->num_counters * sizeof(msrs->counters[0]));
+		memcpy(msrs->controls, rmsrs->controls,
+		       model->num_controls * sizeof(msrs->controls[0]));
+	}
 	nmi_cpu_save_registers(msrs);
 }
 
@@ -195,6 +206,7 @@
 static int nmi_setup(void)
 {
 	int err=0;
+	struct op_msrs *msrs;
 
 	if (!allocate_msrs())
 		return -ENOMEM;
@@ -203,6 +215,14 @@
 		free_msrs();
 		return err;
 	}
+	/*
+	 * MSR reservation should happen only once with the current API,
+	 * otherwise CPU other then the first would fail to allocate.
+	 * We do it here, and then we propagate the CPU#0 addresses to
+	 * other CPUs.
+	 */
+	msrs = &cpu_msrs[0];
+	model->fill_in_addresses(msrs);
 
 	/* We need to serialize save and setup for HT because the subset
 	 * of msrs are distinct for save and setup operations

Re: [patch] fix oprofile SMP ...

[Andi Kleen]

On Friday 18 May 2007 04:18, Davide Libenzi wrote:
> This fixed oprofile being broken on x86-64 SMP. The current reservation
> runs on all CPUs, but the ones following the first, will fail since the
> reservation bitmap has an 1 in the MSR entry.
> The reservation code should really run once, and their addresses used on
> other CPUs. There are other solutions to this, but this is the simplest
> and shorter one that came in my mind. Tested in my dual Opteron 252, and
> working fine here.
> Andi, if you don't like both Ben and my patch, would you mind fixing
> oprofile yourself in some way?

Thanks, but I already did a very similar patch myself

-Andi

i386: Fix K8/core2 oprofile on multiple CPUs

Only try to allocate MSRs once instead of for every CPU.

This assumes the MSRs are the same on all CPUs which is currently
true. P4-HT is a special case for different SMT threads, but the code 
always saves/restores all MSRs so it works identical.

Signed-off-by: Andi Kleen <ak@suse.de>

Index: linux/arch/i386/oprofile/nmi_int.c
===================================================================
--- linux.orig/arch/i386/oprofile/nmi_int.c
+++ linux/arch/i386/oprofile/nmi_int.c
@@ -131,7 +131,6 @@ static void nmi_save_registers(void * du
 {
 	int cpu = smp_processor_id();
 	struct op_msrs * msrs = &cpu_msrs[cpu];
-	model->fill_in_addresses(msrs);
 	nmi_cpu_save_registers(msrs);
 }
 
@@ -195,6 +194,7 @@ static struct notifier_block profile_exc
 static int nmi_setup(void)
 {
 	int err=0;
+	int cpu;
 
 	if (!allocate_msrs())
 		return -ENOMEM;
@@ -207,6 +207,13 @@ static int nmi_setup(void)
 	/* We need to serialize save and setup for HT because the subset
 	 * of msrs are distinct for save and setup operations
 	 */
+
+	/* Assume saved/restored counters are the same on all CPUs */
+	model->fill_in_addresses(&cpu_msrs[0]);
+	for_each_possible_cpu (cpu) {
+		if (cpu != 0)
+			cpu_msrs[cpu] = cpu_msrs[0];
+	}
 	on_each_cpu(nmi_save_registers, NULL, 0, 1);
 	on_each_cpu(nmi_cpu_setup, NULL, 0, 1);
 	nmi_enabled = 1;