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Subject: Re: [PATCH 18/30] x86, kaiser: map virtually-addressed performance
 monitoring buffers
To: Peter Zijlstra <peterz@infradead.org>
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From: Dave Hansen <dave.hansen@linux.intel.com>
Message-ID: <30655167-963f-09e3-f88f-600bb95407e8@linux.intel.com>
Date: Tue, 14 Nov 2017 10:28:50 -0800
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On 11/14/2017 10:20 AM, Peter Zijlstra wrote:
> On Fri, Nov 10, 2017 at 11:31:39AM -0800, Dave Hansen wrote:
>>  static int alloc_ds_buffer(int cpu)
>>  {
>> +	struct debug_store *ds = per_cpu_ptr(&cpu_debug_store, cpu);
>>  
>> +	memset(ds, 0, sizeof(*ds));
> Still wondering about that memset...

My guess is that it was done to mirror the zeroing done by the original
kzalloc().  But, I think you're right that it's zero'd already by virtue
of being static:

static
DEFINE_PER_CPU_SHARED_ALIGNED_USER_MAPPED(struct debug_store,
cpu_debug_store);

I'll queue a cleanup, or update it if I re-post the set.