search for: getcpuid

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