Commit a4234bfc authored Nov 23, 2009 by Ingo Molnar

perf_events: Optimize the swcounter hotpath

The structure init creates a bit memcpy, which shows
up big time in perf annotate output:

: ffffffff810a859d <__perf_sw_event>:
1.68 : ffffffff810a859d: 55 push %rbp
1.69 : ffffffff810a859e: 41 89 fa mov %edi,%r10d
0.01 : ffffffff810a85a1: 49 89 c9 mov %rcx,%r9
0.00 : ffffffff810a85a4: 31 c0 xor %eax,%eax
1.71 : ffffffff810a85a6: b9 16 00 00 00 mov $0x16,%ecx
0.00 : ffffffff810a85ab: 48 89 e5 mov %rsp,%rbp
0.00 : ffffffff810a85ae: 48 83 ec 60 sub $0x60,%rsp
1.52 : ffffffff810a85b2: 48 8d 7d a0 lea -0x60(%rbp),%rdi
85.20 : ffffffff810a85b6: f3 ab rep stos %eax,%es:(%rdi)

None of the callees depends on the structure being pre-initialized,
so only initialize ->addr. This gets rid of the memcpy overhead.

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Mike Galbraith <efault@gmx.de>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent 6e3d8330

kernel/perf_event.c

+5 −5

Original line number	Original line	Diff line number	Diff line
	@@ -3954,12 +3954,12 @@ static void do_perf_sw_event(enum perf_type_id type, u32 event_id,
	void __perf_sw_event(u32 event_id, u64 nr, int nmi,		void __perf_sw_event(u32 event_id, u64 nr, int nmi,
	struct pt_regs *regs, u64 addr)		struct pt_regs *regs, u64 addr)
	{		{
	struct perf_sample_data data = {		struct perf_sample_data data;
	.addr = addr,
	};

	do_perf_sw_event(PERF_TYPE_SOFTWARE, event_id, nr, nmi,		data.addr = addr;
	&data, regs);		data.raw = NULL;

			do_perf_sw_event(PERF_TYPE_SOFTWARE, event_id, nr, nmi, &data, regs);
	}		}

	static void perf_swevent_read(struct perf_event *event)		static void perf_swevent_read(struct perf_event *event)