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clocksource/drivers/hyperv: Enable TSC page clocksource on 32bit

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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
This commit is contained in:
Vitaly Kuznetsov
2019-08-22 10:36:30 +02:00
committed by Thomas Gleixner
parent bd00cd52d5
commit 3e2d94535a
4 changed files with 6 additions and 22 deletions
Download Patch File Download Diff File Expand all files Collapse all files

8
include/clocksource/hyperv_timer.h
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@@ -28,12 +28,10 @@ extern void hv_stimer_cleanup(unsigned int cpu);
extern void hv_stimer_global_cleanup(void);
extern void hv_stimer0_isr(void);
#if IS_ENABLED(CONFIG_HYPERV)
#ifdef CONFIG_HYPERV_TIMER
extern struct clocksource *hyperv_cs;
extern void hv_init_clocksource(void);
#endif /* CONFIG_HYPERV */
#ifdef CONFIG_HYPERV_TSCPAGE
extern struct ms_hyperv_tsc_page *hv_get_tsc_page(void);
static inline notrace u64
@@ -91,7 +89,7 @@ hv_read_tsc_page(const struct ms_hyperv_tsc_page *tsc_pg)
return hv_read_tsc_page_tsc(tsc_pg, &cur_tsc);
}
#else /* CONFIG_HYPERV_TSC_PAGE */
#else /* CONFIG_HYPERV_TIMER */
static inline struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
{
return NULL;
@@ -102,6 +100,6 @@ static inline u64 hv_read_tsc_page_tsc(const struct ms_hyperv_tsc_page *tsc_pg,
{
return U64_MAX;
}
#endif /* CONFIG_HYPERV_TSCPAGE */
#endif /* CONFIG_HYPERV_TIMER */
#endif