[tip:perf/core] perf report: Documentation average IPC and IPC coverage

[tip-bot for Jin Yao]

Commit-ID:  eb58157b92bfdddc5257f9a170edd3db96e96748
Gitweb:     https://git.kernel.org/tip/eb58157b92bfdddc5257f9a170edd3db96e96748
Author:     Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
AuthorDate: Fri, 30 Nov 2018 21:54:57 +0800
Committer:  Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
CommitDate: Fri, 30 Nov 2018 17:14:52 -0300

perf report: Documentation average IPC and IPC coverage

Add explanations for new columns "IPC" and "IPC coverage" in perf
documentation.

 v5:
 ---
 Update the description according to Ingo's comments.

Signed-off-by: Jin Yao <yao.jin@xxxxxxxxxxxxxxx>
Reviewed-by: Ingo Molnar <mingo@xxxxxxxxxx>
Reviewed-by: Jiri Olsa <jolsa@xxxxxxxxxx>
Cc: Alexander Shishkin <alexander.shishkin@xxxxxxxxxxxxxxx>
Cc: Andi Kleen <ak@xxxxxxxxxxxxxxx>
Cc: Kan Liang <kan.liang@xxxxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Link: http://lkml.kernel.org/r/1543586097-27632-5-git-send-email-yao.jin@xxxxxxxxxxxxxxx
Signed-off-by: Arnaldo Carvalho de Melo <acme@xxxxxxxxxx>
---
 tools/perf/Documentation/perf-report.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/Documentation/perf-report.txt b/tools/perf/Documentation/perf-report.txt
index 474a4941f65d..ed2bf37ab132 100644
--- a/tools/perf/Documentation/perf-report.txt
+++ b/tools/perf/Documentation/perf-report.txt
@@ -126,6 +126,14 @@ OPTIONS
 	And default sort keys are changed to comm, dso_from, symbol_from, dso_to
 	and symbol_to, see '--branch-stack'.
 
+	When the sort key symbol is specified, columns "IPC" and "IPC Coverage"
+	are enabled automatically. Column "IPC" reports the average IPC per function
+	and column "IPC coverage" reports the percentage of instructions with
+	sampled IPC in this function. IPC means Instruction Per Cycle. If it's low,
+	it indicates there may be a performance bottleneck when the function is
+	executed, such as a memory access bottleneck. If a function has high overhead
+	and low IPC, it's worth further analyzing it to optimize its performance.
+
 	If the --mem-mode option is used, the following sort keys are also available
 	(incompatible with --branch-stack):
 	symbol_daddr, dso_daddr, locked, tlb, mem, snoop, dcacheline.