Re: [PATCH] perf_events: fix bug in hw_perf_enable()
From: Peter Zijlstra
Date: Mon Feb 01 2010 - 10:35:31 EST
On Mon, 2010-02-01 at 14:50 +0200, Stephane Eranian wrote:
> We cannot assume that because hwc->idx == assign[i], we
> can avoid reprogramming the counter in hw_perf_enable().
>
> The event may have been scheduled out and another event
> may have been programmed into this counter. Thus, we need
> a more robust way of verifying if the counter still
> contains config/data related to an event.
>
> This patch adds a generation number to each counter on each
> cpu. Using this mechanism we can verify reliabilty whether the
> content of a counter corresponds to an event.
>
> Signed-off-by: Stephane Eranian <eranian@xxxxxxxxxx>
Thanks, got it.
btw, I've also added the below, from what I can make from the docs fixed
counter 2 is identical to arch perf event 0x013c, as per table A-1 and
A-7. Both are called CPU_CLK_UNHALTED.REF, except for Core2, where
0x013c is called CPU_CLK_UNHALTED.BUS.
---
Subject: perf_events, x86: Fixup fixed counter constraints
From: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
Date: Mon Feb 01 15:36:30 CET 2010
Patch 1da53e0230 ("perf_events, x86: Improve x86 event scheduling")
lost us one of the fixed purpose counters and then ed8777fc13
("perf_events, x86: Fix event constraint masks") broke it even
further.
Widen the fixed event mask to event+umask and specify the full config
for each of the 3 fixed purpose counters. Then let the init code fill
out the placement for the GP regs based on the cpuid info.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@xxxxxxxxx>
LKML-Reference: <new-submission>
---
arch/x86/include/asm/perf_event.h | 2 +-
arch/x86/kernel/cpu/perf_event.c | 38 ++++++++++++++++++++++++++++++--------
2 files changed, 31 insertions(+), 9 deletions(-)
Index: linux-2.6/arch/x86/include/asm/perf_event.h
===================================================================
--- linux-2.6.orig/arch/x86/include/asm/perf_event.h
+++ linux-2.6/arch/x86/include/asm/perf_event.h
@@ -50,7 +50,7 @@
INTEL_ARCH_INV_MASK| \
INTEL_ARCH_EDGE_MASK|\
INTEL_ARCH_UNIT_MASK|\
- INTEL_ARCH_EVTSEL_MASK)
+ INTEL_ARCH_EVENT_MASK)
#define ARCH_PERFMON_UNHALTED_CORE_CYCLES_SEL 0x3c
#define ARCH_PERFMON_UNHALTED_CORE_CYCLES_UMASK (0x00 << 8)
Index: linux-2.6/arch/x86/kernel/cpu/perf_event.c
===================================================================
--- linux-2.6.orig/arch/x86/kernel/cpu/perf_event.c
+++ linux-2.6/arch/x86/kernel/cpu/perf_event.c
@@ -243,8 +243,18 @@ static struct event_constraint intel_cor
static struct event_constraint intel_core2_event_constraints[] =
{
- FIXED_EVENT_CONSTRAINT(0xc0, (0x3|(1ULL<<32))), /* INSTRUCTIONS_RETIRED */
- FIXED_EVENT_CONSTRAINT(0x3c, (0x3|(1ULL<<33))), /* UNHALTED_CORE_CYCLES */
+ FIXED_EVENT_CONSTRAINT(0x00c0, 1ULL << 32), /* INST_RETIRED.ANY */
+ FIXED_EVENT_CONSTRAINT(0x003c, 1ULL << 33), /* CPU_CLK_UNHALTED.CORE */
+ /*
+ * FIXED_EVENT_CONSTRAINT(0x013c, 1ULL << 34), CPU_CLK_UNHALTED.REF
+ *
+ * Core2 has Fixed Counter 2 listed as CPU_CLK_UNHALTED.REF and event
+ * 0x013c as CPU_CLK_UNHALTED.BUS and specifies there is a fixed
+ * ratio between these counters.
+ *
+ * TODO: find/measure the fixed ratio and apply it so that we can
+ * enable this fixed purpose counter in a transparent way.
+ */
INTEL_EVENT_CONSTRAINT(0x10, 0x1), /* FP_COMP_OPS_EXE */
INTEL_EVENT_CONSTRAINT(0x11, 0x2), /* FP_ASSIST */
INTEL_EVENT_CONSTRAINT(0x12, 0x2), /* MUL */
@@ -259,8 +269,9 @@ static struct event_constraint intel_cor
static struct event_constraint intel_nehalem_event_constraints[] =
{
- FIXED_EVENT_CONSTRAINT(0xc0, (0xf|(1ULL<<32))), /* INSTRUCTIONS_RETIRED */
- FIXED_EVENT_CONSTRAINT(0x3c, (0xf|(1ULL<<33))), /* UNHALTED_CORE_CYCLES */
+ FIXED_EVENT_CONSTRAINT(0x00c0, 1ULL << 32), /* INST_RETIRED.ANY */
+ FIXED_EVENT_CONSTRAINT(0x003c, 1ULL << 33), /* CPU_CLK_UNHALTED.CORE */
+ FIXED_EVENT_CONSTRAINT(0x013c, 1ULL << 34), /* CPU_CLK_UNHALTED.REF */
INTEL_EVENT_CONSTRAINT(0x40, 0x3), /* L1D_CACHE_LD */
INTEL_EVENT_CONSTRAINT(0x41, 0x3), /* L1D_CACHE_ST */
INTEL_EVENT_CONSTRAINT(0x42, 0x3), /* L1D_CACHE_LOCK */
@@ -274,8 +285,9 @@ static struct event_constraint intel_neh
static struct event_constraint intel_westmere_event_constraints[] =
{
- FIXED_EVENT_CONSTRAINT(0xc0, (0xf|(1ULL<<32))), /* INSTRUCTIONS_RETIRED */
- FIXED_EVENT_CONSTRAINT(0x3c, (0xf|(1ULL<<33))), /* UNHALTED_CORE_CYCLES */
+ FIXED_EVENT_CONSTRAINT(0x00c0, 1ULL << 32), /* INST_RETIRED.ANY */
+ FIXED_EVENT_CONSTRAINT(0x003c, 1ULL << 33), /* CPU_CLK_UNHALTED.CORE */
+ FIXED_EVENT_CONSTRAINT(0x013c, 1ULL << 34), /* CPU_CLK_UNHALTED.REF */
INTEL_EVENT_CONSTRAINT(0x51, 0x3), /* L1D */
INTEL_EVENT_CONSTRAINT(0x60, 0x1), /* OFFCORE_REQUESTS_OUTSTANDING */
INTEL_EVENT_CONSTRAINT(0x63, 0x3), /* CACHE_LOCK_CYCLES */
@@ -284,8 +296,9 @@ static struct event_constraint intel_wes
static struct event_constraint intel_gen_event_constraints[] =
{
- FIXED_EVENT_CONSTRAINT(0xc0, (0x3|(1ULL<<32))), /* INSTRUCTIONS_RETIRED */
- FIXED_EVENT_CONSTRAINT(0x3c, (0x3|(1ULL<<33))), /* UNHALTED_CORE_CYCLES */
+ FIXED_EVENT_CONSTRAINT(0x00c0, 1ULL << 32), /* INST_RETIRED.ANY */
+ FIXED_EVENT_CONSTRAINT(0x003c, 1ULL << 33), /* CPU_CLK_UNHALTED.CORE */
+ FIXED_EVENT_CONSTRAINT(0x013c, 1ULL << 34), /* CPU_CLK_UNHALTED.REF */
EVENT_CONSTRAINT_END
};
@@ -2602,6 +2615,7 @@ static void __init pmu_check_apic(void)
void __init init_hw_perf_events(void)
{
+ struct event_constraint *c;
int err;
pr_info("Performance Events: ");
@@ -2650,6 +2664,14 @@ void __init init_hw_perf_events(void)
__EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_events) - 1,
0, x86_pmu.num_events);
+ for_each_event_constraint(c, x86_pmu.event_constraints) {
+ if (c->cmask != INTEL_ARCH_FIXED_MASK)
+ continue;
+
+ c->idxmsk64[0] |= (1ULL << x86_pmu.num_events) - 1;
+ c->weight += x86_pmu.num_events;
+ }
+
pr_info("... version: %d\n", x86_pmu.version);
pr_info("... bit width: %d\n", x86_pmu.event_bits);
pr_info("... generic registers: %d\n", x86_pmu.num_events);
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/