linux-kernel - [PATCH] perf: Completely remove possibility to override MAX_NR

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Message-ID: <bfa19c0a3a40d10a053a2c7d3219eee2098e3b38.1746190831.git.christophe.leroy@csgroup.eu>
Date: Fri,  2 May 2025 15:02:02 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: Peter Zijlstra <peterz@...radead.org>,
	Ingo Molnar <mingo@...hat.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Namhyung Kim <namhyung@...nel.org>,
	Mark Rutland <mark.rutland@....com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Adrian Hunter <adrian.hunter@...el.com>,
	"Liang, Kan" <kan.liang@...ux.intel.com>,
	Leo Yan <leo.yan@....com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
	linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	bpf@...r.kernel.org
Subject: [PATCH] perf: Completely remove possibility to override MAX_NR_CPUS

Commit 21b8732eb447 ("perf tools: Allow overriding MAX_NR_CPUS at
compile time") added the capability to override MAX_NR_CPUS. At
that time it was necessary to reduce the huge amount of RAM used
by static stats variables.

But this has been unnecessary since commit 6a1e2c5c2673 ("perf stat:
Remove a set of shadow stats static variables"), and
commit e8399d34d568 ("libperf cpumap: Hide/reduce scope of
MAX_NR_CPUS") broke the build in that case because it failed to
add the guard around the new definition of MAX_NR_CPUS.

So cleanup things and remove guards completely to officialise it
is not necessary anymore to override MAX_NR_CPUS.

Link: https://lore.kernel.org/all/8c8553387ebf904a9e5a93eaf643cb01164d9fb3.1736188471.git.christophe.leroy@csgroup.eu/
Fixes: e8399d34d568 ("libperf cpumap: Hide/reduce scope of MAX_NR_CPUS")
Signed-off-by: Christophe Leroy <christophe.leroy@...roup.eu>
---
 tools/perf/perf.h                        | 2 --
 tools/perf/util/bpf_skel/kwork_top.bpf.c | 2 --
 2 files changed, 4 deletions(-)

diff --git a/tools/perf/perf.h b/tools/perf/perf.h
index 3cb40965549f..e004178472d9 100644
--- a/tools/perf/perf.h
+++ b/tools/perf/perf.h
@@ -2,9 +2,7 @@
 #ifndef _PERF_PERF_H
 #define _PERF_PERF_H
 
-#ifndef MAX_NR_CPUS
 #define MAX_NR_CPUS			4096
-#endif
 
 enum perf_affinity {
 	PERF_AFFINITY_SYS = 0,
diff --git a/tools/perf/util/bpf_skel/kwork_top.bpf.c b/tools/perf/util/bpf_skel/kwork_top.bpf.c
index 73e32e063030..6673386302e2 100644
--- a/tools/perf/util/bpf_skel/kwork_top.bpf.c
+++ b/tools/perf/util/bpf_skel/kwork_top.bpf.c
@@ -18,9 +18,7 @@ enum kwork_class_type {
 };
 
 #define MAX_ENTRIES     102400
-#ifndef MAX_NR_CPUS
 #define MAX_NR_CPUS     4096
-#endif
 #define PF_KTHREAD      0x00200000
 #define MAX_COMMAND_LEN 16
 
-- 
2.47.0