perf p4 events aliases

Hi Don, if you have a chance could you please check if this patch does a trick for nmi-watchdog and perf top? The idea is to use aliases as being proposed early.

Note I commented out hw_watchdog_set_attr method to be sure this hook doesn't take place so you get "defined but not used" warning but it's known to happen.

Some details -- I think alias should be allowed for general events only so any raw event will never fit aliasing feature.

Compile tested only, so I guess most probably something will goes wrong or fail, but anyway ;) Thanks!

Patch is on top of current -tip/perf/core

| commit 931da6137e8e8c622f59251e8b645467aea293f1

Cyrill

---
 arch/x86/include/asm/perf_event_p4.h |    6 ++
 arch/x86/kernel/cpu/perf_event_p4.c  |   80 +++++++++++++++++++++++++++++++++--
 2 files changed, 82 insertions(+), 4 deletions(-)

Index: linux-2.6.git/arch/x86/include/asm/perf_event_p4.h
===================================================================

arch/x86/include/asm/perf_event_p4.h +6 -0

@@ -757,6 +757,12 @@ enum P4_ESCR_EMASKS {
 #define P4_PEBS_CONFIG_MASK		0xff
 
 /*
+ * If event may have alias it should be marked
+ * with special bit.
+ */
+#define P4_CONFIG_ALIASABLE		(1 << 9)
+
+/*
  * mem: Only counters MSR_IQ_COUNTER4 (16) and
  * MSR_IQ_COUNTER5 (17) are allowed for PEBS sampling
  */

Index: linux-2.6.git/arch/x86/kernel/cpu/perf_event_p4.c
===================================================================

arch/x86/kernel/cpu/perf_event_p4.c +76 -5

@@ -570,11 +570,72 @@ static __initconst const u64 p4_hw_cache
  },
 };
 
+/*
+ * Because of Netburst being quite restricted in now
+ * many similar events can run simultaneously we use
+ * that named event aliases, ie different events which
+ * have the same functionallity but use non-intersected
+ * ESCR/CCCR/couter registers which relax restrictions a
+ * bit and run two or more semi-same events together.
+ * This is done transparently to a user space.
+ *
+ * Never set P4_CONFIG_HT bit here nor the P4_PEBS_METRIC,
+ * they either up-to-dated automatically either not appliable
+ * at all, so be really carefull choosing aliases.
+ *
+ */
+struct p4_event_alias {
+	u64 orig;
+	u64 alter;
+} p4_event_aliases[] = {
+  {
+	.orig	=
+		p4_config_pack_escr(P4_ESCR_EVENT(P4_EVENT_GLOBAL_POWER_EVENTS)		|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_GLOBAL_POWER_EVENTS, RUNNING)),
+	.alter	=
+		p4_config_pack_escr(P4_ESCR_EVENT(P4_EVENT_EXECUTION_EVENT)		|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, NBOGUS0)|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, NBOGUS1)|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, NBOGUS2)|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, NBOGUS3)|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, BOGUS0)	|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, BOGUS1)	|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, BOGUS2)	|
+				    P4_ESCR_EMASK_BIT(P4_EVENT_EXECUTION_EVENT, BOGUS3))|
+		p4_config_pack_cccr(P4_CCCR_THRESHOLD(15) | P4_CCCR_COMPLEMENT		|
+				    P4_CCCR_COMPARE),
+  },
+};
+
+static u64 p4_get_alias_event(u64 config)
+{
+	int i;
+
+	if (!(config & P4_CONFIG_ALIASABLE))
+		return 0;
+
+	config &= P4_CONFIG_MASK;
+
+	/*
+	 * If an event was previously already swapped to
+	 * alter config we can swap it back when needed.
+	 */
+	for (i = 0; i < ARRAY_SIZE(p4_event_aliases); i++) {
+		if (config == p4_event_aliases[i].orig)
+			return p4_event_aliases[i].alter | P4_CONFIG_ALIASABLE;
+		else if (config == p4_event_aliases[i].alter)
+			return p4_event_aliases[i].orig | P4_CONFIG_ALIASABLE;
+	}
+
+	return 0;
+}
+
 static u64 p4_general_events[PERF_COUNT_HW_MAX] = {
   /* non-halted CPU clocks */
   [PERF_COUNT_HW_CPU_CYCLES] =
 	p4_config_pack_escr(P4_ESCR_EVENT(P4_EVENT_GLOBAL_POWER_EVENTS)		|
-		P4_ESCR_EMASK_BIT(P4_EVENT_GLOBAL_POWER_EVENTS, RUNNING)),
+		P4_ESCR_EMASK_BIT(P4_EVENT_GLOBAL_POWER_EVENTS, RUNNING))	|
+		P4_CONFIG_ALIASABLE,
 
   /*
    * retired instructions

@@ -1159,6 +1220,7 @@ static int p4_pmu_schedule_events(struct
 	struct p4_event_bind *bind;
 	unsigned int i, thread, num;
 	int cntr_idx, escr_idx;
+	u64 config_alias;
 
 	bitmap_zero(used_mask, X86_PMC_IDX_MAX);
 	bitmap_zero(escr_mask, P4_ESCR_MSR_TABLE_SIZE);

@@ -1167,6 +1229,7 @@ static int p4_pmu_schedule_events(struct
 
 		hwc = &cpuc->event_list[i]->hw;
 		thread = p4_ht_thread(cpu);
+again:
 		bind = p4_config_get_bind(hwc->config);
 		escr_idx = p4_get_escr_idx(bind->escr_msr[thread]);
 		if (unlikely(escr_idx == -1))

@@ -1180,8 +1243,17 @@ static int p4_pmu_schedule_events(struct
 		}
 
 		cntr_idx = p4_next_cntr(thread, used_mask, bind);
-		if (cntr_idx == -1 || test_bit(escr_idx, escr_mask))
-			goto done;
+		if (cntr_idx == -1 || test_bit(escr_idx, escr_mask)) {
+			/*
+			 * Probably an event alias is still available.
+			 */
+			config_alias = p4_get_alias_event(hwc->config);
+			if (!config_alias)
+				goto done;
+			/* Don't forget to restore HT */
+			hwc->config = thread ? p4_set_ht_bit(config_alias) : config_alias;
+			goto again;
+		}
 
 		p4_pmu_swap_config_ts(hwc, cpu);
 		if (assign)

@@ -1218,7 +1290,7 @@ static __initconst const struct x86_pmu 
 	.cntval_bits		= ARCH_P4_CNTRVAL_BITS,
 	.cntval_mask		= ARCH_P4_CNTRVAL_MASK,
 	.max_period		= (1ULL << (ARCH_P4_CNTRVAL_BITS - 1)) - 1,
-	.hw_watchdog_set_attr	= p4_hw_watchdog_set_attr,
+	/* .hw_watchdog_set_attr	= p4_hw_watchdog_set_attr, */
 	.hw_config		= p4_hw_config,
 	.schedule_events	= p4_pmu_schedule_events,
 	/*
--

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/

Quoted 3 lines · Cyrill Gorcunov

Hi Don, if you have a chance could you please check if this patch does a trick for nmi-watchdog and perf top? The idea is to use aliases as being proposed early.

Hmm, didn't work for me. The watchdog seems to work but 'perf top' showed nothing (even after 30 seconds). I tried this on Linus's latest -tip and Ingo's perf/core -tip. No luck.

Cheers,
Don

Quoted 3 lines · Cyrill Gorcunov

Hi Don, if you have a chance could you please check if this patch does a trick for nmi-watchdog and perf top? The idea is to use aliases as being proposed early.

Hmm, didn't work for me. The watchdog seems to work but 'perf top' showed nothing (even after 30 seconds). I tried this on Linus's latest -tip and Ingo's perf/core -tip. No luck.

Quoted 5 lines · Don Zickus

Quoted 3 lines · Cyrill Gorcunov

Hi Don, if you have a chance could you please check if this patch does a trick for nmi-watchdog and perf top? The idea is to use aliases as being proposed early.

Quoted 3 lines

Hmm, didn't work for me. The watchdog seems to work but 'perf top' showed nothing (even after 30 seconds). I tried this on Linus's latest -tip and Ingo's perf/core -tip. No luck.

Yeah I did the same. Without the patch, perf top works, with the patch I get nothing.