diff options
| author | Vitaly Kuznetsov <vkuznets@redhat.com> | 2019-08-22 10:36:30 +0200 |
|---|---|---|
| committer | Thomas Gleixner <tglx@linutronix.de> | 2019-08-23 16:59:54 +0200 |
| commit | 3e2d94535adb2df15f3907e4b4c7cd8a5a4c2b5a (patch) | |
| tree | aa53940e9cf060d6afd783cdaeea0a998101722a /include/clocksource | |
| parent | bd00cd52d5be655a2f217e2ed74b91a71cb2b14f (diff) | |
| download | lwn-3e2d94535adb2df15f3907e4b4c7cd8a5a4c2b5a.tar.gz lwn-3e2d94535adb2df15f3907e4b4c7cd8a5a4c2b5a.zip | |
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
Diffstat (limited to 'include/clocksource')
| -rw-r--r-- | include/clocksource/hyperv_timer.h | 8 |
1 files changed, 3 insertions, 5 deletions
diff --git a/include/clocksource/hyperv_timer.h b/include/clocksource/hyperv_timer.h index a821deb8ecb2..422f5e5237be 100644 --- a/include/clocksource/hyperv_timer.h +++ b/include/clocksource/hyperv_timer.h @@ -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 |