linux-kernel - [PATCH 3/3] perf/hw_breakpoint: Skip modify_bp

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Message-ID: <20250903075144.3722848-3-wangjinchao600@gmail.com>
Date: Wed,  3 Sep 2025 15:51:40 +0800
From: Jinchao Wang <wangjinchao600@...il.com>
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>,
	linux-perf-users@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	Jinchao Wang <wangjinchao600@...il.com>
Subject: [PATCH 3/3] perf/hw_breakpoint: Skip modify_bp_slot() if slot index unchanged

Only call modify_bp_slot() when the old and new breakpoint types map to
different slot indices.

This avoids unnecessary release/reserve operations and improves efficiency.

Signed-off-by: Jinchao Wang <wangjinchao600@...il.com>
---
 kernel/events/hw_breakpoint.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 1db2c5e24d0e..6fed9521baf2 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -752,6 +752,7 @@ modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *a
 {
 	struct arch_hw_breakpoint hw = { };
 	int err;
+	enum bp_type_idx old_type_idx, new_type_idx;
 
 	err = hw_breakpoint_parse(bp, attr, &hw);
 	if (err)
@@ -766,7 +767,9 @@ modify_user_hw_breakpoint_check(struct perf_event *bp, struct perf_event_attr *a
 			return -EINVAL;
 	}
 
-	if (bp->attr.bp_type != attr->bp_type) {
+	old_type_idx = find_slot_idx(bp->attr.bp_type);
+	new_type_idx = find_slot_idx(attr->bp_type);
+	if (old_type_idx != new_type_idx) {
 		err = modify_bp_slot(bp, bp->attr.bp_type, attr->bp_type);
 		if (err)
 			return err;
-- 
2.43.0