linux-kernel - [PATCH v5 4/7] perf: Shrink the size of the recursion counter.

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Message-ID: <20240704170424.1466941-5-bigeasy@linutronix.de>
Date: Thu,  4 Jul 2024 19:03:38 +0200
From: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To: linux-perf-users@...r.kernel.org,
	linux-kernel@...r.kernel.org
Cc: Adrian Hunter <adrian.hunter@...el.com>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Frederic Weisbecker <frederic@...nel.org>,
	Ian Rogers <irogers@...gle.com>,
	Ingo Molnar <mingo@...hat.com>,
	Jiri Olsa <jolsa@...nel.org>,
	Kan Liang  <kan.liang@...ux.intel.com>,
	Marco Elver <elver@...gle.com>,
	Mark Rutland <mark.rutland@....com>,
	Namhyung Kim <namhyung@...nel.org>,
	Peter Zijlstra <peterz@...radead.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: [PATCH v5 4/7] perf: Shrink the size of the recursion counter.

There are four recursion counter, one for each context. The type of the
counter is `int' but the counter is used as `bool' since it is only
incremented if zero.
The main goal here is to shrink the whole struct into 32bit int which
can later be added task_struct into an existing hole.

Reduce the type of the recursion counter to an unsigned char, keep the
increment/ decrement operation.

Tested-by: Marco Elver <elver@...gle.com>
Signed-off-by: Sebastian Andrzej Siewior <bigeasy@...utronix.de>
---
 kernel/events/callchain.c | 2 +-
 kernel/events/core.c      | 2 +-
 kernel/events/internal.h  | 4 ++--
 3 files changed, 4 insertions(+), 4 deletions(-)

diff --git a/kernel/events/callchain.c b/kernel/events/callchain.c
index 1273be84392cf..ad57944b6c40e 100644
--- a/kernel/events/callchain.c
+++ b/kernel/events/callchain.c
@@ -29,7 +29,7 @@ static inline size_t perf_callchain_entry__sizeof(void)
 				 sysctl_perf_event_max_contexts_per_stack));
 }
 
-static DEFINE_PER_CPU(int, callchain_recursion[PERF_NR_CONTEXTS]);
+static DEFINE_PER_CPU(u8, callchain_recursion[PERF_NR_CONTEXTS]);
 static atomic_t nr_callchain_events;
 static DEFINE_MUTEX(callchain_mutex);
 static struct callchain_cpus_entries *callchain_cpus_entries;
diff --git a/kernel/events/core.c b/kernel/events/core.c
index c278aefa94e76..bd4b81bf63b6d 100644
--- a/kernel/events/core.c
+++ b/kernel/events/core.c
@@ -9776,7 +9776,7 @@ struct swevent_htable {
 	int				hlist_refcount;
 
 	/* Recursion avoidance in each contexts */
-	int				recursion[PERF_NR_CONTEXTS];
+	u8				recursion[PERF_NR_CONTEXTS];
 };
 
 static DEFINE_PER_CPU(struct swevent_htable, swevent_htable);
diff --git a/kernel/events/internal.h b/kernel/events/internal.h
index 5150d5f84c033..f9a3244206b20 100644
--- a/kernel/events/internal.h
+++ b/kernel/events/internal.h
@@ -208,7 +208,7 @@ arch_perf_out_copy_user(void *dst, const void *src, unsigned long n)
 
 DEFINE_OUTPUT_COPY(__output_copy_user, arch_perf_out_copy_user)
 
-static inline int get_recursion_context(int *recursion)
+static inline int get_recursion_context(u8 *recursion)
 {
 	unsigned char rctx = interrupt_context_level();
 
@@ -221,7 +221,7 @@ static inline int get_recursion_context(int *recursion)
 	return rctx;
 }
 
-static inline void put_recursion_context(int *recursion, int rctx)
+static inline void put_recursion_context(u8 *recursion, int rctx)
 {
 	barrier();
 	recursion[rctx]--;
-- 
2.45.2