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Date: Mon, 4 Jul 2022 17:05:07 +0200 From: Marco Elver <elver@...gle.com> To: elver@...gle.com, Peter Zijlstra <peterz@...radead.org>, Frederic Weisbecker <frederic@...nel.org>, Ingo Molnar <mingo@...nel.org> Cc: Thomas Gleixner <tglx@...utronix.de>, Arnaldo Carvalho de Melo <acme@...nel.org>, Mark Rutland <mark.rutland@....com>, Alexander Shishkin <alexander.shishkin@...ux.intel.com>, Jiri Olsa <jolsa@...hat.com>, Namhyung Kim <namhyung@...nel.org>, Dmitry Vyukov <dvyukov@...gle.com>, Michael Ellerman <mpe@...erman.id.au>, linuxppc-dev@...ts.ozlabs.org, linux-perf-users@...r.kernel.org, x86@...nel.org, linux-sh@...r.kernel.org, kasan-dev@...glegroups.com, linux-kernel@...r.kernel.org Subject: [PATCH v3 07/14] 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@...gle.com> Reviewed-by: Dmitry Vyukov <dvyukov@...gle.com> --- 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 a3fb846705eb..f319bd26b030 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 9fb66d358d81..9c9bf17666a5 100644 --- a/kernel/events/hw_breakpoint.c +++ b/kernel/events/hw_breakpoint.c @@ -124,10 +124,12 @@ static __init int init_breakpoint_slots(void) } #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) { -- 2.37.0.rc0.161.g10f37bed90-goog
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