Re: [PATCH V4 01/13] perf/core, x86: Add PERF_SAMPLE_DATA_PAGE_SIZE

Liang, Kan
2019-02-01T14:46:05Z

On 2/1/2019 4:22 AM, Peter Zijlstra wrote:
> On Thu, Jan 31, 2019 at 12:27:54PM -0800, kan.liang@linux.intel.com wrote:
>> diff --git a/arch/x86/events/core.c b/arch/x86/events/core.c
>> index 374a197..229a73b 100644
>> --- a/arch/x86/events/core.c
>> +++ b/arch/x86/events/core.c
>> @@ -2578,3 +2578,34 @@ void perf_get_x86_pmu_capability(struct x86_pmu_capability *cap)
>> cap->events_mask_len = x86_pmu.events_mask_len;
>> }
>> EXPORT_SYMBOL_GPL(perf_get_x86_pmu_capability);
>> +
>> +u64 perf_get_page_size(u64 virt)
>> +{
>> + unsigned long flags;
>> + unsigned int level;
>> + pte_t *pte;
>> +
>> + if (!virt)
>> + return 0;
>> +
>> + /*
>> + * Interrupts are disabled, so it prevents any tear down
>> + * of the page tables.
>> + * See the comment near struct mmu_table_batch.
>> + */
>> + local_irq_save(flags);
>> + if (virt >= TASK_SIZE)
>> + pte = lookup_address(virt, &level);
>> + else {
>> + if (current->mm) {
>> + pte = lookup_address_in_pgd(pgd_offset(current->mm, virt),
>> + virt, &level);
>> + } else
>> + level = PG_LEVEL_NUM;
>> + }
>> + local_irq_restore(flags);
>> + if (level >= PG_LEVEL_NUM)
>> + return 0;
>> +
>> + return (u64)page_level_size(level);
>> +}
>
> *sigh* there really isn't anything x86 specific there.

OK. I will split the patch and move the common code to a dedicated patch
in V5. I will try the proposed code and do some tests on X86.

> >> diff --git a/kernel/events/core.c b/kernel/events/core.c
>> index 236bb8d..d233f45 100644
>> --- a/kernel/events/core.c
>> +++ b/kernel/events/core.c
>> @@ -6352,6 +6358,12 @@ static u64 perf_virt_to_phys(u64 virt)
>> return phys_addr;
>> }
>>
>> +/* Return page size of given virtual address. IRQ-safe required. */
>> +u64 __weak perf_get_page_size(u64 virt)
>> +{
>> + return 0;
>> +}
>> +
>> static struct perf_callchain_entry __empty_callchain = { .nr = 0, };
>>
>> struct perf_callchain_entry *
>
> How about something like so instead?
>
> (completely untested, will likely make your grandma eat puppies
That's not funny!

Kan