linux-kernel - [PATCH v2 7/9] perf c2c: Correct LLC load hit metrics

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Date:   Thu, 15 Oct 2020 15:45:46 +0100
From:   Leo Yan <leo.yan@...aro.org>
To:     Arnaldo Carvalho de Melo <acme@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Mark Rutland <mark.rutland@....com>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Jiri Olsa <jolsa@...hat.com>,
        Namhyung Kim <namhyung@...nel.org>,
        Andi Kleen <ak@...ux.intel.com>,
        Kan Liang <kan.liang@...ux.intel.com>,
        Ian Rogers <irogers@...gle.com>, Joe Mario <jmario@...hat.com>,
        David Ahern <dsahern@...il.com>,
        Don Zickus <dzickus@...hat.com>, Al Grant <Al.Grant@....com>,
        James Clark <james.clark@....com>, linux-kernel@...r.kernel.org
Cc:     Leo Yan <leo.yan@...aro.org>
Subject: [PATCH v2 7/9] perf c2c: Correct LLC load hit metrics

"rmt_hit" is accounted into two metrics: one is accounted into the
metrics "LLC Ld Miss" (see the function llc_miss() for calculation
"llcmiss"); and it's accounted into metrics "LLC Load Hit".  Thus,
for the literal meaning, it is contradictory that "rmt_hit" is
accounted for both "LLC Ld Miss" (LLC miss) and "LLC Load Hit"
(LLC hit).

Thus this is easily to introduce confusion: "LLC Load Hit" gives
impression that all items belong to it are LLC hit; in fact "rmt_hit"
is LLC miss and remote cache hit.

To give out clear semantics for metric "LLC Load Hit", "rmt_hit" is
moved out from it and changes "LLC Load Hit" to contain two items:

  LLC Load Hit = LLC's hit ("ld_llchit") + LLC's hitm ("lcl_hitm")

For output alignment, adjusts the header for "LLC Load Hit".

Signed-off-by: Leo Yan <leo.yan@...aro.org>
Tested-by: Joe Mario <jmario@...hat.com>
---
 tools/perf/builtin-c2c.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tools/perf/builtin-c2c.c b/tools/perf/builtin-c2c.c
index 2292261b40a2..61fb939a4e70 100644
--- a/tools/perf/builtin-c2c.c
+++ b/tools/perf/builtin-c2c.c
@@ -1432,7 +1432,7 @@ static struct c2c_dimension dim_ld_l2hit = {
 };
 
 static struct c2c_dimension dim_ld_llchit = {
-	.header		= HEADER_SPAN("-- LLC Load Hit --", "LclHit", 1),
+	.header		= HEADER_SPAN("- LLC Load Hit --", "LclHit", 1),
 	.name		= "ld_lclhit",
 	.cmp		= ld_llchit_cmp,
 	.entry		= ld_llchit_entry,
@@ -2853,7 +2853,7 @@ static int perf_c2c__report(int argc, const char **argv)
 			"tot_stores,"
 			"stores_l1hit,stores_l1miss,"
 			"ld_fbhit,ld_l1hit,ld_l2hit,"
-			"ld_lclhit,ld_rmthit,"
+			"ld_lclhit,lcl_hitm,"
 			"ld_llcmiss,"
 			"dram_lcl,dram_rmt",
 			c2c.display == DISPLAY_TOT ? "tot_hitm" :
-- 
2.17.1