On Thu, 7 Nov 2019, Vitaly Kuznetsov wrote: > Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> writes: > > > When sending an IPI to a single CPU there is no need to deal with cpumasks. > > With 2 CPU guest on WS2019 I'm seeing a minor (like 3%, 8043 -> 7761 CPU > > cycles) improvement with smp_call_function_single() loop benchmark. The > > optimization, however, is tiny and straitforward. Also, send_ipi_one() is > > important for PV spinlock kick. > > > > I was also wondering if it would make sense to switch to using regular > > APIC IPI send for CPU > 64 case but no, it is twice as expesive (12650 CPU > > cycles for __send_ipi_mask_ex() call, 26000 for orig_apic.send_IPI(cpu, > > vector)). > > > > Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx> > > --- > > Changes since v2: > > - Check VP number instead of CPU number against >= 64 [Michael] > > - Check for VP_INVAL > > Hi Sasha, > > do you have plans to pick this up for hyperv-next or should we ask x86 > folks to? I'm picking up the constant TSC one anyway, so I can just throw that in as well. Thanks, tglx
