Messages in this thread | | | Date | Thu, 27 Oct 2016 11:33:34 +0200 | From | Peter Zijlstra <> | Subject | Re: Getting interrupt every million cache misses |
| |
On Thu, Oct 27, 2016 at 11:11:04AM +0200, Pavel Machek wrote: > How to work around rowhammer, break my system _and_ make kernel perf > maintainers scream at the same time: (:-) ) > > I think I got the place now. Let me try...
Lol ;-)
> > diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c > index d31735f..ce83f5e 100644 > --- a/arch/x86/events/core.c > +++ b/arch/x86/events/core.c > @@ -1495,6 +1495,11 @@ perf_event_nmi_handler(unsigned int cmd, struct pt_regs *regs) > > perf_sample_event_took(finish_clock - start_clock); > > + /* Here */ > + { > + udelay(58000); > + } > + > return ret; > } > NOKPROBE_SYMBOL(perf_event_nmi_handler);
Like you guess, not quite ;-)
I think you want to register a custom overflow handler with your event.
So you get something like:
struct perf_event_attr rh_attr = { .type = PERF_TYPE_HARDWARE, .config = PERF_COUNT_HW_CACHE_MISSES, .size = sizeof(struct perf_event_attr), .pinned = 1, .sample_period = 1000000, };
static DEFINE_PER_CPU(struct perf_event *, rh_event); static DEFINE_PER_CPU(u64, rh_timestamp);
static void rh_overflow(struct perf_event *event, struct perf_sample_data *data, struct pt_regs *regs) { u64 *ts = this_cpu_ptr(&rh_timestamp); /* this is NMI context */ u64 now = ktime_get_mono_fast_ns(); s64 delta = now - *ts;
*ts = now;
if (delta > 64 * NSEC_PER_USEC) udelay(58000); }
__init int my_module_init() { int cpu;
/* XXX borken vs hotplug */
for_each_online_cpu(cpu) { struct perf_event *event = per_cpu(event, cpu);
event = perf_event_create_kernel_counter(&rh_attr, cpu, NULL, rh_overflow, NULL); if (!event) /* meh */ ;
} }
__exit void my_module_exit() { int cpu;
for_each_online_cpu(cpu) { struct perf_event *event = per_cpu(event, cpu);
if (event) perf_event_release_kernel(event); } }
| |