linux-kernel - Re: [RFC][PATCH 7/7] perf/annotate: Add branch stack / basic block information

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Date:	Fri, 8 Jul 2016 18:36:32 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	acme@...nel.org, linux-kernel@...r.kernel.org, andi@...stfloor.org,
	eranian@...gle.com, jolsa@...nel.org,
	torvalds@...ux-foundation.org, davidcc@...gle.com,
	alexander.shishkin@...ux.intel.com, namhyung@...nel.org,
	kan.liang@...el.com, khandual@...ux.vnet.ibm.com
Subject: Re: [RFC][PATCH 7/7] perf/annotate: Add branch stack / basic block
 information

On Fri, Jul 08, 2016 at 06:27:33PM +0200, Peter Zijlstra wrote:

> I've been thinking of filtering all targets and branches that are
> smaller than 0.1% in order to avoid this, but so far I've just been
> ignoring these things.

Like so... seems to 'work'.

---
 tools/perf/util/annotate.c | 45 ++++++++++++++++++++++++++-------------------
 1 file changed, 26 insertions(+), 19 deletions(-)

diff --git a/tools/perf/util/annotate.c b/tools/perf/util/annotate.c
index 8eeb151..c78b16f0 100644
--- a/tools/perf/util/annotate.c
+++ b/tools/perf/util/annotate.c
@@ -907,6 +907,7 @@ static void annotate__branch_printf(struct block_range *br, u64 addr)
 #if 1
 	if (br->is_target && br->start == addr) {
 		struct block_range *branch = br;
+		double p;
 
 		/*
 		 * Find matching branch to our target.
@@ -914,31 +915,37 @@ static void annotate__branch_printf(struct block_range *br, u64 addr)
 		while (!branch->is_branch)
 			branch = block_range__next(branch);
 
-		if (emit_comment) {
-			emit_comment = false;
-			printf("\t#");
-		}
+		p = 100 *(double)br->entry / branch->coverage;
 
-		/*
-		 * The percentage of coverage joined at this target in relation
-		 * to the next branch.
-		 */
-		printf(" +%.2f%%", 100*(double)br->entry / branch->coverage);
+		if (p > 0.1) {
+			if (emit_comment) {
+				emit_comment = false;
+				printf("\t#");
+			}
+
+			/*
+			 * The percentage of coverage joined at this target in relation
+			 * to the next branch.
+			 */
+			printf(" +%.2f%%", p);
+		}
 	}
 #endif
 	if (br->is_branch && br->end == addr) {
+		double p = 100*(double)br->taken / br->coverage;
 
-		if (emit_comment) {
-			emit_comment = false;
-			printf("\t#");
-		}
+		if (p > 0.1) {
+			if (emit_comment) {
+				emit_comment = false;
+				printf("\t#");
+			}
 
-		/*
-		 * The percentage of coverage leaving at this branch, and
-		 * its prediction ratio.
-		 */
-		printf(" -%.2f%% / %.2f%%", 100*(double)br->taken / br->coverage,
-					    100*(double)br->pred  / br->taken);
+			/*
+			 * The percentage of coverage leaving at this branch, and
+			 * its prediction ratio.
+			 */
+			printf(" -%.2f%% (p:%.2f%%)", p, 100*(double)br->pred  / br->taken);
+		}
 	}
 }