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linux-next/arch/x86/include/asm/vdso
Vitaly Kuznetsov 3e2d94535a clocksource/drivers/hyperv: Enable TSC page clocksource on 32bit
There is no particular reason to not enable TSC page clocksource on
32-bit. mul_u64_u64_shr() is available and despite the increased
computational complexity (compared to 64bit) TSC page is still a huge win
compared to MSR-based clocksource.

In-kernel reads:
  MSR based clocksource: 3361 cycles
  TSC page clocksource: 49 cycles

Reads from userspace (utilizing vDSO in case of TSC page):
  MSR based clocksource: 5664 cycles
  TSC page clocksource: 131 cycles

Enabling TSC page on 32bits allows to get rid of CONFIG_HYPERV_TSCPAGE as
it is now not any different from CONFIG_HYPERV_TIMER.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Michael Kelley <mikelley@microsoft.com>
Link: https://lkml.kernel.org/r/20190822083630.17059-1-vkuznets@redhat.com
2019-08-23 16:59:54 +02:00
..
gettimeofday.h clocksource/drivers/hyperv: Enable TSC page clocksource on 32bit 2019-08-23 16:59:54 +02:00
vsyscall.h x86/vdso: Switch to generic vDSO implementation 2019-06-22 21:21:10 +02:00