Re: [PATCH v4 RESEND 3/5] perf/x86/lbr: Move cpuc->lbr_xsave allocation out of sleeping region

[Like Xu <like.xu@linux.intel.com>]

Hi Namhyung,

On 2021/3/24 9:32, Namhyung Kim wrote:
> Hello,
> 
> On Mon, Mar 22, 2021 at 3:14 PM Like Xu <like.xu@linux.intel.com> wrote:
>> +void reserve_lbr_buffers(struct perf_event *event)
>> +{
>> +       struct kmem_cache *kmem_cache = x86_get_pmu()->task_ctx_cache;
>> +       struct cpu_hw_events *cpuc;
>> +       int cpu;
>> +
>> +       if (!static_cpu_has(X86_FEATURE_ARCH_LBR))
>> +               return;
>> +
>> +       for_each_possible_cpu(cpu) {
>> +               cpuc = per_cpu_ptr(&cpu_hw_events, cpu);
>> +               if (kmem_cache && !cpuc->lbr_xsave && !event->attr.precise_ip)
>> +                       cpuc->lbr_xsave = kmem_cache_alloc(kmem_cache, GFP_KERNEL);
>> +       }
>> +}
> 
> I think we should use kmem_cache_alloc_node().

"kmem_cache_alloc_node - Allocate an object on the specified node"

The reserve_lbr_buffers() is called in __x86_pmu_event_init().
When the LBR perf_event is scheduled to another node, it seems
that we will not call init() and allocate again.

Do you mean use kmem_cache_alloc_node() for each numa_nodes_parsed ?

> 
> Thanks,
> Namhyung
>