Displaying 2 results from an estimated 2 matches for "getcpuid".
Did you mean:
get_cpuid
2014 Apr 18
2
[LLVMdev] multithreaded performance disaster with -fprofile-instr-generate (contention on profile counters)
...omething, there is non-zero chance
> that significant amount of active threads will be mapped onto the same
> shard. And then get back to where we start -- we have significant
> contention.
>
> Ideally it would be something like:
>
> on_thread_rescheduling()
> {
> tid = getcpuid();
> }
>
> but common OSes do not provide necessary interfaces.
>
Note also: if we store tid in a thread-local variable, we'll either have to
load it on every counter increment or keep it in a register,
which by itself will bring additional ~10% slowdown on x86_64. This is why
taki...
2014 Apr 18
2
[LLVMdev] multithreaded performance disaster with -fprofile-instr-generate (contention on profile counters)
On Fri, Apr 18, 2014 at 11:13 AM, Dmitry Vyukov <dvyukov at google.com> wrote:
> Hi,
>
> This is long thread, so I will combine several comments into single email.
>
>
> >> - 8-bit per-thread counters, dumping into central counters on overflow.
> >The overflow will happen very quickly with 8bit counter.
>
> Yes, but it reduces contention by 256x (a thread