diff options
| author | Marco Elver <elver@google.com> | 2022-08-29 14:47:12 +0200 |
|---|---|---|
| committer | Peter Zijlstra <peterz@infradead.org> | 2022-08-30 10:56:22 +0200 |
| commit | 9caf87be118f4639537404eeb67dd444a3716e9a (patch) | |
| tree | 59e4d4f8eb569b097d9e61ca9fa3bfbc53c06ce8 | |
| parent | perf/hw_breakpoint: Optimize constant number of breakpoint slots (diff) | |
| download | linux-9caf87be118f4639537404eeb67dd444a3716e9a.tar.xz linux-9caf87be118f4639537404eeb67dd444a3716e9a.zip | |
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@google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Reviewed-by: Dmitry Vyukov <dvyukov@google.com>
Acked-by: Ian Rogers <irogers@google.com>
Link: https://lore.kernel.org/r/20220829124719.675715-8-elver@google.com
| -rw-r--r-- | include/linux/hw_breakpoint.h | 1 | ||||
| -rw-r--r-- | 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 @@ 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) { |