[PATCH V2 1/1] perf/x86: filter branches for PEBS event

[PATCH V2 1/1] perf/x86: filter branches for PEBS event

[kan.liang]

From: Kan Liang <kan.liang@intel.com>

For supporting Intel LBR branches filtering, Intel LBR sharing logic
mechanism is introduced from commit b36817e88630 ("perf/x86: Add Intel
LBR sharing logic"). It modifies __intel_shared_reg_get_constraints to
config lbr_sel, which is finally used to set LBR_SELECT.
However, the intel_shared_regs_constraints is called after
intel_pebs_constraints. The PEBS event will return immediately after
intel_pebs_constraints. So it's impossible to filter branches for PEBS
event.

This patch move intel_shared_regs_constraints ahead of
intel_pebs_constraints.
We can safely do that because the intel_shared_regs_constraints only
returns emptyconstraint if its rejecting the event, otherwise it returns
NULL such that we continue calling intel_pebs_constraints and
x86_get_event_constraint.

Signed-off-by: Kan Liang <kan.liang@intel.com>
---

Changes since V1:
 - Move all shared regs ahead of intel_pebs_constraints
 - Modify the description and quote Peter's comments.

 arch/x86/kernel/cpu/perf_event_intel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 9f1dd18..83bee99 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1635,11 +1635,11 @@ intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event
 	if (c)
 		return c;
 
-	c = intel_pebs_constraints(event);
+	c = intel_shared_regs_constraints(cpuc, event);
 	if (c)
 		return c;
 
-	c = intel_shared_regs_constraints(cpuc, event);
+	c = intel_pebs_constraints(event);
 	if (c)
 		return c;
 
-- 
1.8.3.1

[tip:perf/core] perf/x86/intel: Filter branches for PEBS event

[tip-bot for Kan Liang]

Commit-ID:  687805e4a60fe83a11556c041840161f8016a367
Gitweb:     http://git.kernel.org/tip/687805e4a60fe83a11556c041840161f8016a367
Author:     Kan Liang <kan.liang@intel.com>
AuthorDate: Fri, 27 Mar 2015 10:38:25 -0400
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Thu, 2 Apr 2015 17:07:42 +0200

perf/x86/intel: Filter branches for PEBS event

For supporting Intel LBR branches filtering, Intel LBR sharing logic
mechanism is introduced from commit b36817e88630 ("perf/x86: Add Intel
LBR sharing logic"). It modifies __intel_shared_reg_get_constraints() to
config lbr_sel, which is finally used to set LBR_SELECT.

However, the intel_shared_regs_constraints() function is called after
intel_pebs_constraints(). The PEBS event will return immediately after
intel_pebs_constraints(). So it's impossible to filter branches for PEBS
events.

This patch moves intel_shared_regs_constraints() ahead of
intel_pebs_constraints().

We can safely do that because the intel_shared_regs_constraints() function
only returns empty constraint if its rejecting the event, otherwise it
returns NULL such that we continue calling intel_pebs_constraints() and
x86_get_event_constraint().

Signed-off-by: Kan Liang <kan.liang@intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: eranian@google.com
Link: http://lkml.kernel.org/r/1427467105-9260-1-git-send-email-kan.liang@intel.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/kernel/cpu/perf_event_intel.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 498b6d9..40898ab 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1649,11 +1649,11 @@ intel_get_event_constraints(struct cpu_hw_events *cpuc, struct perf_event *event
 	if (c)
 		return c;
 
-	c = intel_pebs_constraints(event);
+	c = intel_shared_regs_constraints(cpuc, event);
 	if (c)
 		return c;
 
-	c = intel_shared_regs_constraints(cpuc, event);
+	c = intel_pebs_constraints(event);
 	if (c)
 		return c;