Commit b68f1d2e authored May 17, 2009 by Ingo Molnar

perf_counter, x86: speed up the scheduling fast-path



We have to set up the LVT entry only at counter init time, not at
every switch-in time.

There's friction between NMI and non-NMI use here - we'll probably
remove the per counter configurability of it - but until then, dont
slow down things ...

[ Impact: micro-optimization ]

Cc: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Srivatsa Vaddagiri <vatsa@in.ibm.com>
Cc: Paul Mackerras <paulus@samba.org>
Cc: Corey Ashford <cjashfor@linux.vnet.ibm.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Marcelo Tosatti <mtosatti@redhat.com>
LKML-Reference: <new-submission>
Signed-off-by: Ingo Molnar <mingo@elte.hu>

parent c0daaf3f

arch/x86/kernel/cpu/perf_counter.c

+2 −3

Original line number	Diff line number	Diff line
		@@ -285,6 +285,7 @@ static int __hw_perf_counter_init(struct perf_counter *counter)
		return -EACCES;
		hwc->nmi = 1;
		}
		perf_counters_lapic_init(hwc->nmi);

		if (!hwc->irq_period)
		hwc->irq_period = x86_pmu.max_period;
		@@ -603,8 +604,6 @@ static int x86_pmu_enable(struct perf_counter *counter)
		hwc->counter_base = x86_pmu.perfctr;
		}

		perf_counters_lapic_init(hwc->nmi);

		x86_pmu.disable(hwc, idx);

		cpuc->counters[idx] = counter;
		@@ -1054,7 +1053,7 @@ void __init init_hw_perf_counters(void)

		pr_info("... counter mask: %016Lx\n", perf_counter_mask);

		perf_counters_lapic_init(0);
		perf_counters_lapic_init(1);
		register_die_notifier(&perf_counter_nmi_notifier);
		}