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Subject[PATCH V2 13/23] perf/x86/intel/lbr: Factor out intel_pmu_store_lbr
Date
From: Kan Liang <kan.liang@linux.intel.com>

The way to store the LBR information from a PEBS LBR record can be
reused in Architecture LBR, because
- The LBR information is stored like a stack. Entry 0 is always the
youngest branch.
- The layout of the LBR INFO MSR is similar.

The LBR information may be retrieved from either the LBR registers
(non-PEBS event) or a buffer (PEBS event). Extend rdlbr_*() to support
both methods.

Explicitly check the invalid entry (0s), which can avoid unnecessary MSR
access if using a non-PEBS event. For a PEBS event, the check should
slightly improve the performance as well. The invalid entries are cut.
The intel_pmu_lbr_filter() doesn't need to check and filter them out.

Cannot share the function with current model-specific LBR read, because
the direction of the LBR growth is opposite.

Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
---
arch/x86/events/intel/lbr.c | 81 +++++++++++++++++++++++++++++++--------------
1 file changed, 56 insertions(+), 25 deletions(-)

diff --git a/arch/x86/events/intel/lbr.c b/arch/x86/events/intel/lbr.c
index 459f1a5..bac18c4 100644
--- a/arch/x86/events/intel/lbr.c
+++ b/arch/x86/events/intel/lbr.c
@@ -348,28 +348,37 @@ static inline void wrlbr_info(unsigned int idx, u64 val)
wrmsrl(x86_pmu.lbr_info + idx, val);
}

-static inline u64 rdlbr_from(unsigned int idx)
+static inline u64 rdlbr_from(unsigned int idx, struct lbr_entry *lbr)
{
u64 val;

+ if (lbr)
+ return lbr->from;
+
rdmsrl(x86_pmu.lbr_from + idx, val);

return lbr_from_signext_quirk_rd(val);
}

-static inline u64 rdlbr_to(unsigned int idx)
+static inline u64 rdlbr_to(unsigned int idx, struct lbr_entry *lbr)
{
u64 val;

+ if (lbr)
+ return lbr->to;
+
rdmsrl(x86_pmu.lbr_to + idx, val);

return val;
}

-static inline u64 rdlbr_info(unsigned int idx)
+static inline u64 rdlbr_info(unsigned int idx, struct lbr_entry *lbr)
{
u64 val;

+ if (lbr)
+ return lbr->info;
+
rdmsrl(x86_pmu.lbr_info + idx, val);

return val;
@@ -387,16 +396,16 @@ wrlbr_all(struct lbr_entry *lbr, unsigned int idx, bool need_info)
static inline bool
rdlbr_all(struct lbr_entry *lbr, unsigned int idx, bool need_info)
{
- u64 from = rdlbr_from(idx);
+ u64 from = rdlbr_from(idx, NULL);

/* Don't read invalid entry */
if (!from)
return false;

lbr->from = from;
- lbr->to = rdlbr_to(idx);
+ lbr->to = rdlbr_to(idx, NULL);
if (need_info)
- lbr->info = rdlbr_info(idx);
+ lbr->info = rdlbr_info(idx, NULL);

return true;
}
@@ -428,7 +437,7 @@ void intel_pmu_lbr_restore(void *ctx)

static bool lbr_is_reset_in_cstate(void *ctx)
{
- return !rdlbr_from(((struct x86_perf_task_context *)ctx)->tos);
+ return !rdlbr_from(((struct x86_perf_task_context *)ctx)->tos, NULL);
}

static void __intel_pmu_lbr_restore(void *ctx)
@@ -687,8 +696,8 @@ void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
u16 cycles = 0;
int lbr_flags = lbr_desc[lbr_format];

- from = rdlbr_from(lbr_idx);
- to = rdlbr_to(lbr_idx);
+ from = rdlbr_from(lbr_idx, NULL);
+ to = rdlbr_to(lbr_idx, NULL);

/*
* Read LBR call stack entries
@@ -700,7 +709,7 @@ void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
if (lbr_format == LBR_FORMAT_INFO && need_info) {
u64 info;

- info = rdlbr_info(lbr_idx);
+ info = rdlbr_info(lbr_idx, NULL);
mis = !!(info & LBR_INFO_MISPRED);
pred = !mis;
in_tx = !!(info & LBR_INFO_IN_TX);
@@ -755,6 +764,42 @@ void intel_pmu_lbr_read_64(struct cpu_hw_events *cpuc)
cpuc->lbr_stack.hw_idx = tos;
}

+static void intel_pmu_store_lbr(struct cpu_hw_events *cpuc,
+ struct lbr_entry *entries)
+{
+ struct perf_branch_entry *e;
+ struct lbr_entry *lbr;
+ u64 from, to, info;
+ int i;
+
+ for (i = 0; i < x86_pmu.lbr_nr; i++) {
+ lbr = entries ? &entries[i] : NULL;
+ e = &cpuc->lbr_entries[i];
+
+ from = rdlbr_from(i, lbr);
+ /*
+ * Read LBR entries until invalid entry (0s) is detected.
+ */
+ if (!from)
+ break;
+
+ to = rdlbr_to(i, lbr);
+ info = rdlbr_info(i, lbr);
+
+ e->from = from;
+ e->to = to;
+ e->mispred = !!(info & LBR_INFO_MISPRED);
+ e->predicted = !(info & LBR_INFO_MISPRED);
+ e->in_tx = !!(info & LBR_INFO_IN_TX);
+ e->abort = !!(info & LBR_INFO_ABORT);
+ e->cycles = info & LBR_INFO_CYCLES;
+ e->type = 0;
+ e->reserved = 0;
+ }
+
+ cpuc->lbr_stack.nr = i;
+}
+
void intel_pmu_lbr_read(void)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
@@ -1192,9 +1237,6 @@ intel_pmu_lbr_filter(struct cpu_hw_events *cpuc)
void intel_pmu_store_pebs_lbrs(struct pebs_lbr *lbr)
{
struct cpu_hw_events *cpuc = this_cpu_ptr(&cpu_hw_events);
- int i;
-
- cpuc->lbr_stack.nr = x86_pmu.lbr_nr;

/* Cannot get TOS for large PEBS */
if (cpuc->n_pebs == cpuc->n_large_pebs)
@@ -1202,19 +1244,8 @@ void intel_pmu_store_pebs_lbrs(struct pebs_lbr *lbr)
else
cpuc->lbr_stack.hw_idx = intel_pmu_lbr_tos();

- for (i = 0; i < x86_pmu.lbr_nr; i++) {
- u64 info = lbr->lbr[i].info;
- struct perf_branch_entry *e = &cpuc->lbr_entries[i];
+ intel_pmu_store_lbr(cpuc, lbr->lbr);

- e->from = lbr->lbr[i].from;
- e->to = lbr->lbr[i].to;
- e->mispred = !!(info & LBR_INFO_MISPRED);
- e->predicted = !(info & LBR_INFO_MISPRED);
- e->in_tx = !!(info & LBR_INFO_IN_TX);
- e->abort = !!(info & LBR_INFO_ABORT);
- e->cycles = info & LBR_INFO_CYCLES;
- e->reserved = 0;
- }
intel_pmu_lbr_filter(cpuc);
}

--
2.7.4
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