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SubjectRe: [PATCH] perf_events: AMD event scheduling (v3)
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On Mon, 2010-02-08 at 17:17 +0200, Stephane Eranian wrote:
> This patch adds correct AMD Northbridge event scheduling.
> It must be applied on top tip-x86 + hw_perf_enable() fix.
>
> NB events are events measuring L3 cache, Hypertransport
> traffic. They are identified by an event code >= 0xe0.
> They measure events on the Northbride which is shared
> by all cores on a package. NB events are counted on a
> shared set of counters. When a NB event is programmed
> in a counter, the data actually comes from a shared
> counter. Thus, access to those counters needs to be
> synchronized.
>
> We implement the synchronization such that no two cores
> can be measuring NB events using the same counters. Thus,
> we maintain a per-NB * allocation table. The available slot
> is propagated using the event_constraint structure.
>
> The 2nd version takes into account the changes on how
> constraints are stored by the scheduling code.
>
> The 3rd version fixes formatting issues, code readability
> and one bug in amd_put_event_constraints().
>
> Signed-off-by: Stephane Eranian <eranian@google.com>

OK, took this with the below merged in.

---
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
@@ -81,7 +81,7 @@ struct event_constraint {
};

struct amd_nb {
- int nb_id; /* Northbridge id */
+ int nb_id; /* NorthBridge id */
int refcnt; /* reference count */
struct perf_event *owners[X86_PMC_IDX_MAX];
struct event_constraint event_constraints[X86_PMC_IDX_MAX];
@@ -2268,7 +2268,7 @@ static inline int amd_is_nb_event(struct
u64 val = hwc->config & K7_EVNTSEL_EVENT_MASK;
/* event code : bits [35-32] | [7-0] */
val = (val >> 24) | (val & 0xff);
- return val >= 0x0e0;
+ return val >= 0xe00;
}

static void amd_put_event_constraints(struct cpu_hw_events *cpuc,
@@ -2301,28 +2301,29 @@ static void amd_put_event_constraints(st
}

/*
- * AMD64 Northbridge events need special treatment because
+ * AMD64 NorthBridge events need special treatment because
* counter access needs to be synchronized across all cores
* of a package. Refer to BKDG section 3.12
*
* NB events are events measuring L3 cache, Hypertransport
- * traffic. They are identified by an event code >= 0xe0.
- * They measure events on the Northbride which is shared
+ * traffic. They are identified by an event code >= 0xe00.
+ * They measure events on the NorthBride which is shared
* by all cores on a package. NB events are counted on a
* shared set of counters. When a NB event is programmed
* in a counter, the data actually comes from a shared
* counter. Thus, access to those counters needs to be
* synchronized.
+ *
* We implement the synchronization such that no two cores
* can be measuring NB events using the same counters. Thus,
- * we maintain a per-NB * allocation table. The available slot
+ * we maintain a per-NB allocation table. The available slot
* is propagated using the event_constraint structure.
*
* We provide only one choice for each NB event based on
* the fact that only NB events have restrictions. Consequently,
* if a counter is available, there is a guarantee the NB event
* will be assigned to it. If no slot is available, an empty
- * constraint is returned and scheduling will evnetually fail
+ * constraint is returned and scheduling will eventually fail
* for this event.
*
* Note that all cores attached the same NB compete for the same
@@ -2753,7 +2754,7 @@ static struct amd_nb *amd_alloc_nb(int c

/*
* initialize all possible NB constraints
- */
+ */
for (i = 0; i < x86_pmu.num_events; i++) {
set_bit(i, nb->event_constraints[i].idxmsk);
nb->event_constraints[i].weight = 1;
@@ -2773,9 +2774,6 @@ static void amd_pmu_cpu_online(int cpu)
/*
* function may be called too early in the
* boot process, in which case nb_id is bogus
- *
- * for BSP, there is an explicit call from
- * amd_pmu_init()
*/
nb_id = amd_get_nb_id(cpu);
if (nb_id == BAD_APICID)
@@ -2839,7 +2837,10 @@ static __init int amd_pmu_init(void)
memcpy(hw_cache_event_ids, amd_hw_cache_event_ids,
sizeof(hw_cache_event_ids));

- /* initialize BSP */
+ /*
+ * explicitly initialize the boot cpu, other cpus will get
+ * the cpu hotplug callbacks from smp_init()
+ */
amd_pmu_cpu_online(smp_processor_id());
return 0;
}



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