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SubjectRe: [RFC PATCH 2/3 v2] perf: Implement Nehalem uncore pmu
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On Sun, 2010-11-21 at 20:46 +0800, Andi Kleen wrote:
> >
> > 2. Uncore pmu NMI handling
> >
> > All the 4 cores are programmed to receive uncore counter overflow
> > interrupt. The NMI handler(running on 1 of the 4 cores) handle all
> > counters enabled by all 4 cores.
>
> Really for uncore monitoring there is no need to use an NMI handler.
> You can't profile a core anyways, so you can just delay the reporting
> a little bit. It may simplify the code to not use one here
> and just use an ordinary handler.

OK, I can use on ordinary interrupt handler here.

>
> In general since there is already much trouble with overloaded
> NMI events avoiding new NMIs is a good idea.
>
>
>
> > +
> > +static struct node_hw_events *uncore_events[MAX_NUMNODES];
>
> Don't declare static arrays with MAX_NUMNODES, that number can be
> very large and cause unnecessary bloat. Better use per CPU data or similar
> (e.g. with alloc_percpu)

I really need is a per physical cpu data here, is alloc_percpu enough?

>
> > + /*
> > + * The hw event starts counting from this event offset,
> > + * mark it to be able to extra future deltas:
> > + */
> > + local64_set(&hwc->prev_count, (u64)-left);
>
> Your use of local* seems dubious. That is only valid if it's really
> all on the same CPU. Is that really true?

Good catch! That is not true.

The interrupt handler is running on one core and the
data(hwc->prev_count) maybe on another core.

Any idea to set this cross-core data?

>
> > +static int uncore_pmu_add(struct perf_event *event, int flags)
> > +{
> > + int node = numa_node_id();
>
> this should be still package id

Understand, this is in my TODO.

>
> > + /* Check CPUID signatures: 06_1AH, 06_1EH, 06_1FH */
> > + model = eax.split.model | (eax.split.ext_model << 4);
> > + if (eax.split.family != 6 || (model != 0x1A && model != 0x1E && model !=
> > 0x1F))
> > + return;
>
> You can just get that from boot_cpu_data, no need to call cpuid

Nice, will use it.

>
> > +#include <linux/perf_event.h>
> > +#include <linux/capability.h>
> > +#include <linux/notifier.h>
> > +#include <linux/hardirq.h>
> > +#include <linux/kprobes.h>
> > +#include <linux/module.h>
> > +#include <linux/kdebug.h>
> > +#include <linux/sched.h>
> > +#include <linux/uaccess.h>
> > +#include <linux/slab.h>
> > +#include <linux/highmem.h>
> > +#include <linux/cpu.h>
> > +#include <linux/bitops.h>
>
> Do you really need all these includes?

Only

#include <linux/perf_event.h>
#include <linux/kprobes.h>
#include <linux/hardirq.h>
#include <linux/slab.h>

are needed.

Thanks for the comments.
Lin Ming




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