linux-kernel - [PATCH v3 4/5] perf/record: add documentation for sampling skid ip

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Date:   Tue,  7 Nov 2017 23:56:36 -0800
From:   Stephane Eranian <eranian@...gle.com>
To:     linux-kernel@...r.kernel.org
Cc:     acme@...hat.com, peterz@...radead.org, mingo@...e.hu,
        ak@...ux.intel.com, kan.liang@...el.com, jolsa@...hat.com
Subject: [PATCH v3 4/5] perf/record: add documentation for sampling skid ip

This patch adds documentation to describe how to use the skid
ip support with perf record. The sample type can be provided
per event as follows: pmu_instance/...,skid-ip=1/

For instance on Intel X86:

$ perf record -e cpu/event=0xc5,skid-ip=1/pp

does record the precise address of retired branches and their target.

Signed-off-by: Stephane Eranian <eranian@...gle.com>
---
 tools/perf/Documentation/perf-record.txt | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 5a626ef666c2..3b156fa03c99 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -57,6 +57,14 @@ OPTIONS
 			 FP mode, "dwarf" for DWARF mode, "lbr" for LBR mode and
 			 "no" for disable callgraph.
 	  - 'stack-size': user stack size for dwarf mode
+	  - 'skid_ip' : boolean, captures the unmodified interrupt instruction pointer
+			(IP) in each sample. Usually with event-based sampling, the IP
+			has skid and rarely point to the instruction which caused the
+			event to overflow. On some architectures, the hardware can eliminate
+			the skid and perf_events returns it as the IP with precise sampling is
+			enabled. But for certain measurements, it may be useful to have both
+			the correct and skid ip. This option enable capturing the skid ip in
+			additional to the corrected ip. Default is: false
 
           See the linkperf:perf-list[1] man page for more parameters.
 
-- 
2.7.4