The following commit has been merged into the perf/core branch of tip:
Commit-ID: 9caf87be118f4639537404eeb67dd444a3716e9a
Gitweb: https://git.kernel.org/tip/9caf87be118f4639537404eeb67dd444a3716e9a
Author: Marco Elver <elver@xxxxxxxxxx>
AuthorDate: Mon, 29 Aug 2022 14:47:12 +02:00
Committer: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
CommitterDate: Tue, 30 Aug 2022 10:56:22 +02:00
perf/hw_breakpoint: Make hw_breakpoint_weight() inlinable
Due to being a __weak function, hw_breakpoint_weight() will cause the
compiler to always emit a call to it. This generates unnecessarily bad
code (register spills etc.) for no good reason; in fact it appears in
profiles of `perf bench -r 100 breakpoint thread -b 4 -p 128 -t 512`:
...
0.70% [kernel] [k] hw_breakpoint_weight
...
While a small percentage, no architecture defines its own
hw_breakpoint_weight() nor are there users outside hw_breakpoint.c,
which makes the fact it is currently __weak a poor choice.
Change hw_breakpoint_weight()'s definition to follow a similar protocol
to hw_breakpoint_slots(), such that if <asm/hw_breakpoint.h> defines
hw_breakpoint_weight(), we'll use it instead.
The result is that it is inlined and no longer shows up in profiles.
Signed-off-by: Marco Elver <elver@xxxxxxxxxx>
Signed-off-by: Peter Zijlstra (Intel) <peterz@xxxxxxxxxxxxx>
Reviewed-by: Dmitry Vyukov <dvyukov@xxxxxxxxxx>
Acked-by: Ian Rogers <irogers@xxxxxxxxxx>
Link: https://lore.kernel.org/r/20220829124719.675715-8-elver@xxxxxxxxxx
---
include/linux/hw_breakpoint.h | 1 -
kernel/events/hw_breakpoint.c | 4 +++-
2 files changed, 3 insertions(+), 2 deletions(-)
diff --git a/include/linux/hw_breakpoint.h b/include/linux/hw_breakpoint.h
index a3fb846..f319bd2 100644
--- a/include/linux/hw_breakpoint.h
+++ b/include/linux/hw_breakpoint.h
@@ -80,7 +80,6 @@ extern int dbg_reserve_bp_slot(struct perf_event *bp);
extern int dbg_release_bp_slot(struct perf_event *bp);
extern int reserve_bp_slot(struct perf_event *bp);
extern void release_bp_slot(struct perf_event *bp);
-int hw_breakpoint_weight(struct perf_event *bp);
int arch_reserve_bp_slot(struct perf_event *bp);
void arch_release_bp_slot(struct perf_event *bp);
void arch_unregister_hw_breakpoint(struct perf_event *bp);
diff --git a/kernel/events/hw_breakpoint.c b/kernel/events/hw_breakpoint.c
index 9fb66d3..9c9bf17 100644
--- a/kernel/events/hw_breakpoint.c
+++ b/kernel/events/hw_breakpoint.c
@@ -124,10 +124,12 @@ err:
}
#endif
-__weak int hw_breakpoint_weight(struct perf_event *bp)
+#ifndef hw_breakpoint_weight
+static inline int hw_breakpoint_weight(struct perf_event *bp)
{
return 1;
}
+#endif
static inline enum bp_type_idx find_slot_idx(u64 bp_type)
{
|