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SubjectRe: [PATCH] perf/core: fix mlock accounting in perf_mmap()
Date
Song Liu <songliubraving@fb.com> writes:

>> On Jan 20, 2020, at 12:24 AM, Alexander Shishkin <alexander.shishkin@linux.intel.com> wrote:
>>
>> Song Liu <songliubraving@fb.com> writes:
>>
>>> sysctl_perf_event_mlock and user->locked_vm can change value
>>> independently, so we can't guarantee:
>>>
>>> user->locked_vm <= user_lock_limit
>>
>> This means: if the sysctl got sufficiently decreased, so that the
>> existing locked_vm exceeds it, we need to deal with the overflow, right?
>
> Reducing sysctl is one way to generate the overflow. Another way is to
> call setrlimit() from user space to allow bigger user->locked_vm.

You mean RLIMIT_MEMLOCK? That's a limit on mm->pinned_vm. Doesn't affect
user->locked_vm.

Regards,
--
Alex

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