linux-kernel - [PATCH v2] perf docs: Refine the description for the buffer size

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Message-Id: <20240812093459.2575278-1-leo.yan@arm.com>
Date: Mon, 12 Aug 2024 10:34:59 +0100
From: Leo Yan <leo.yan@....com>
To: Arnaldo Carvalho de Melo <acme@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Namhyung Kim <namhyung@...nel.org>,
	Jiri Olsa <jolsa@...nel.org>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	James Clark <james.clark@...aro.org>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Leo Yan <leo.yan@....com>
Subject: [PATCH v2] perf docs: Refine the description for the buffer size

Current description for the AUX trace buffer size is misleading. When a
user specifies the option '-m,512M', it represents a size value in bytes
(512MiB) but not 512M pages (512M x 4KiB regard to a page of 4KiB).

Make the document clear that the normal buffer and the AUX tracing
buffer share the same semantics. Syncs the documents for consistent
text.

Signed-off-by: Leo Yan <leo.yan@....com>
Reviewed-by: James Clark <james.clark@...aro.org>
---

Changes from v1:
 Synced for all documents for consistent description (James)

 tools/perf/Documentation/perf-kvm.txt    | 6 +++---
 tools/perf/Documentation/perf-record.txt | 9 +++++----
 tools/perf/Documentation/perf-top.txt    | 4 ++--
 tools/perf/Documentation/perf-trace.txt  | 4 ++--
 4 files changed, 12 insertions(+), 11 deletions(-)

diff --git a/tools/perf/Documentation/perf-kvm.txt b/tools/perf/Documentation/perf-kvm.txt
index b66be66fe836..c26524d38f47 100644
--- a/tools/perf/Documentation/perf-kvm.txt
+++ b/tools/perf/Documentation/perf-kvm.txt
@@ -115,9 +115,9 @@ STAT LIVE OPTIONS
 
 -m::
 --mmap-pages=::
-    Number of mmap data pages (must be a power of two) or size
-    specification with appended unit character - B/K/M/G. The
-    size is rounded up to have nearest pages power of two value.
+        Number of mmap data pages (must be a power of two) or size
+        specification in bytes with appended unit character - B/K/M/G.
+        The size is rounded up to the nearest power-of-two page value.
 
 -a::
 --all-cpus::
diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 41e36b4dc765..242223240a08 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -273,10 +273,11 @@ OPTIONS
 -m::
 --mmap-pages=::
 	Number of mmap data pages (must be a power of two) or size
-	specification with appended unit character - B/K/M/G. The
-	size is rounded up to have nearest pages power of two value.
-	Also, by adding a comma, the number of mmap pages for AUX
-	area tracing can be specified.
+	specification in bytes with appended unit character - B/K/M/G.
+	The size is rounded up to the nearest power-of-two page value.
+	By adding a comma, an additional parameter with the same
+	semantics used for the normal mmap areas can be specified for
+	AUX tracing area.
 
 -g::
 	Enables call-graph (stack chain/backtrace) recording for both
diff --git a/tools/perf/Documentation/perf-top.txt b/tools/perf/Documentation/perf-top.txt
index 667e5102075e..af3e4230c72f 100644
--- a/tools/perf/Documentation/perf-top.txt
+++ b/tools/perf/Documentation/perf-top.txt
@@ -83,8 +83,8 @@ Default is to monitor all CPUS.
 -m <pages>::
 --mmap-pages=<pages>::
 	Number of mmap data pages (must be a power of two) or size
-	specification with appended unit character - B/K/M/G. The
-	size is rounded up to have nearest pages power of two value.
+	specification in bytes with appended unit character - B/K/M/G.
+	The size is rounded up to the nearest power-of-two page value.
 
 -p <pid>::
 --pid=<pid>::
diff --git a/tools/perf/Documentation/perf-trace.txt b/tools/perf/Documentation/perf-trace.txt
index f0da8cf63e9a..6e0cc50bbc13 100644
--- a/tools/perf/Documentation/perf-trace.txt
+++ b/tools/perf/Documentation/perf-trace.txt
@@ -106,8 +106,8 @@ filter out the startup phase of the program, which is often very different.
 -m::
 --mmap-pages=::
 	Number of mmap data pages (must be a power of two) or size
-	specification with appended unit character - B/K/M/G. The
-	size is rounded up to have nearest pages power of two value.
+	specification in bytes with appended unit character - B/K/M/G.
+	The size is rounded up to the nearest power-of-two page value.
 
 -C::
 --cpu::
-- 
2.34.1