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SubjectRe: [PATCH 2/3] perf/x86/amd/uncore: Dynamically allocate uncore counters
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On 1/12/2017 3:20 AM, Peter Zijlstra wrote:
> On Wed, Jan 11, 2017 at 10:02:17AM -0600, Janakarajan Natarajan wrote:
>> This patch updates the AMD uncore driver to support AMD Family17h
>> processors. In Family17h, there are two extra last level cache counters.
>> The counters are, therefore, allocated dynamically based on the family.
>>
>> The cpu hotplug up callback function is refactored to better manage
>> failure conditions.
>>
>> Signed-off-by: Janakarajan Natarajan <Janakarajan.Natarajan@amd.com>
>> ---
>> arch/x86/events/amd/uncore.c | 141 +++++++++++++++++++++++++++++++------------
>> 1 file changed, 104 insertions(+), 37 deletions(-)
>>
>> diff --git a/arch/x86/events/amd/uncore.c b/arch/x86/events/amd/uncore.c
>> index 24c8537..7ab92f7 100644
>> --- a/arch/x86/events/amd/uncore.c
>> +++ b/arch/x86/events/amd/uncore.c
>> @@ -22,13 +22,16 @@
>>
>> #define NUM_COUNTERS_NB 4
>> #define NUM_COUNTERS_L2 4
>> -#define MAX_COUNTERS NUM_COUNTERS_NB
>> +#define NUM_COUNTERS_L3 6
>>
>> #define RDPMC_BASE_NB 6
>> #define RDPMC_BASE_LLC 10
>>
>> #define COUNTER_SHIFT 16
>>
>> +static int num_counters_llc;
>> +static int num_counters_nb;
>> +
>> static HLIST_HEAD(uncore_unused_list);
>>
>> struct amd_uncore {
>> @@ -40,7 +43,7 @@ struct amd_uncore {
>> u32 msr_base;
>> cpumask_t *active_mask;
>> struct pmu *pmu;
>> - struct perf_event *events[MAX_COUNTERS];
>> + struct perf_event **events;
>> struct hlist_node node;
>> };
> Why bother with the dynamic allocation crud? Why not simply set
> MAX_COUNTERS to 6 and be happy?
My reasoning behind using dynamic allocation was to prevent memory from
being allocated when not needed on a per cpu basis. If memory isn't a
consideration, I can send a v2 without the dynamic memory allocation.

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