linux-kernel - [PATCH v5 2/2] perf record: Update docs regarding the maximum limitation of AUX area

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Message-Id: <20230907004308.25874-3-xueshuai@linux.alibaba.com>
Date:   Thu,  7 Sep 2023 08:43:08 +0800
From:   Shuai Xue <xueshuai@...ux.alibaba.com>
To:     alexander.shishkin@...ux.intel.com, peterz@...radead.org,
        james.clark@....com, leo.yan@...aro.org
Cc:     mingo@...hat.com, baolin.wang@...ux.alibaba.com, acme@...nel.org,
        mark.rutland@....com, jolsa@...nel.org, namhyung@...nel.org,
        irogers@...gle.com, adrian.hunter@...el.com,
        linux-perf-users@...r.kernel.org, linux-kernel@...r.kernel.org,
        nathan@...nel.org, bpf@...r.kernel.org
Subject: [PATCH v5 2/2] perf record: Update docs regarding the maximum limitation of AUX area

The maximum AUX area is limited by the page size of the system. Update
the documentation to reflect this.

Signed-off-by: Shuai Xue <xueshuai@...ux.alibaba.com>
---
 tools/perf/Documentation/perf-record.txt | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index 680396c56bd1..dfc322d6f1f1 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -292,6 +292,17 @@ OPTIONS
 	Also, by adding a comma, the number of mmap pages for AUX
 	area tracing can be specified.
 
+	The maximum AUX area is limited by the maximum physically contiguous
+	memory allocated from slab/slub. It can be calculated with following
+	formula:
+
+	  PAGE_SIZE << MAX_ORDER
+	( ---------------------- ) * PAGE_SIZE
+	   sizeof(page_pointer)
+
+	For example with 4K pages and MAX_ORDER=10 configured, the maximum AUX
+	area is 2GiB.
+
 -g::
 	Enables call-graph (stack chain/backtrace) recording for both
 	kernel space and user space.
-- 
2.39.3