On Tue, 2015-06-02 at 21:29 +0530, Madhavan Srinivasan wrote: > Patch creates a file "nest-pmu-c" to contain nest pmu related functions. "nest-pmu.c" > Patch adds nest pmu init function and cpumask function since Nest pmu units > are per-chip. First online cpu for a given node is picked as > designated thread to read the counter data. > > Subsequent patch adds the hotplug support. > > Cc: Michael Ellerman <m...@ellerman.id.au> > Cc: Benjamin Herrenschmidt <b...@kernel.crashing.org> > Cc: Paul Mackerras <pau...@samba.org> > Cc: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com> > Cc: Anshuman Khandual <khand...@linux.vnet.ibm.com> > Cc: Stephane Eranian <eran...@google.com> > Cc: Preeti U Murthy <pre...@linux.vnet.ibm.com> > Cc: Ingo Molnar <mi...@kernel.org> > Cc: Peter Zijlstra <pet...@infradead.org> > Signed-off-by: Madhavan Srinivasan <ma...@linux.vnet.ibm.com> > --- > arch/powerpc/perf/nest-pmu.c | 70 > ++++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 70 insertions(+) > create mode 100644 arch/powerpc/perf/nest-pmu.c > > diff --git a/arch/powerpc/perf/nest-pmu.c b/arch/powerpc/perf/nest-pmu.c > new file mode 100644 > index 0000000..d4413bb > --- /dev/null > +++ b/arch/powerpc/perf/nest-pmu.c > @@ -0,0 +1,70 @@ > +/* > + * Nest Performance Monitor counter support for POWER8 processors. > + * > + * Copyright 2015 Madhavan Srinivasan, IBM Corporation. > + * > + * This program is free software; you can redistribute it and/or > + * modify it under the terms of the GNU General Public License > + * as published by the Free Software Foundation; either version > + * 2 of the License, or (at your option) any later version. > + */ > + Again, I think this is supposed to be v2 only.
> +#include "nest-pmu.h"
> +
> +static cpumask_t cpu_mask_nest_pmu;
> +
> +static ssize_t cpumask_nest_pmu_get_attr(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + return cpumap_print_to_pagebuf(true, buf, &cpu_mask_nest_pmu);
> +}
> +
> +static DEVICE_ATTR(cpumask, S_IRUGO, cpumask_nest_pmu_get_attr, NULL);
> +
> +static struct attribute *cpumask_nest_pmu_attrs[] = {
> + &dev_attr_cpumask.attr,
> + NULL,
> +};
> +
> +static struct attribute_group cpumask_nest_pmu_attr_group = {
> + .attrs = cpumask_nest_pmu_attrs,
> +};
> +
> +void cpumask_chip(void)
> +{
> + const struct cpumask *l_cpumask;
> + int cpu, nid;
> +
> + if (!cpumask_empty(&cpu_mask_nest_pmu)) {
> + printk(KERN_INFO "cpumask not empty\n");
> + return;
> + }
> +
> + cpu_notifier_register_begin();
> + for_each_online_node(nid) {
> + l_cpumask = cpumask_of_node(nid);
> + cpu = cpumask_first(l_cpumask);
> + cpumask_set_cpu(cpu, &cpu_mask_nest_pmu);
> + }
> +
> + cpu_notifier_register_done();
> +}
It's not clear from the name of this function what it does. I don't
think I actually understand what it does: it appears to register a
notifier on the first cpu of each node; maybe that should be reflected
in the name.
> +static int __init nest_pmu_init(void)
> +{
> + int ret = 0;
> +
> + /*
> + * Lets do this only if we are hypervisor
> + */
> + if (!cur_cpu_spec->oprofile_cpu_type ||
> + strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc64/power8") ||
> + !cpu_has_feature(CPU_FTR_HVMODE))
> + return ret;
> +
> + cpumask_chip();
> +
> + return 0;
> +}
- Where is ret set? I can only see it set when it's defined: the if
statment doesn't change the value of ret as far as I can see...
- Would it be clearer if you said
!(strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc64/power8") == 0)
That would make it clearer that you're trying to get a list of
possible failure conditions.
- Is there really no better way to check if a CPU is a power 8 than an
string comparison?
> +device_initcall(nest_pmu_init);
Regards,
Daniel Axtens
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