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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
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
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
arch/x86/include/asm/vdso/gettimeofday.h
View File

@ -51,7 +51,7 @@ extern struct pvclock_vsyscall_time_info pvclock_page
__attribute__((visibility("hidden")));
#endif
#ifdef CONFIG_HYPERV_TSCPAGE
#ifdef CONFIG_HYPERV_TIMER
extern struct ms_hyperv_tsc_page hvclock_page
__attribute__((visibility("hidden")));
#endif
@ -192,7 +192,7 @@ static u64 vread_pvclock(void)
}
#endif
#ifdef CONFIG_HYPERV_TSCPAGE
#ifdef CONFIG_HYPERV_TIMER
static u64 vread_hvclock(void)
{
return hv_read_tsc_page(&hvclock_page);
@ -215,7 +215,7 @@ static inline u64 __arch_get_hw_counter(s32 clock_mode)
return vread_pvclock();
}
#endif
#ifdef CONFIG_HYPERV_TSCPAGE
#ifdef CONFIG_HYPERV_TIMER
if (clock_mode == VCLOCK_HVCLOCK) {
barrier();
return vread_hvclock();

11
drivers/clocksource/hyperv_timer.c
View File

@ -213,8 +213,6 @@ EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
struct clocksource *hyperv_cs;
EXPORT_SYMBOL_GPL(hyperv_cs);
#ifdef CONFIG_HYPERV_TSCPAGE
static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
@ -245,7 +243,6 @@ static struct clocksource hyperv_cs_tsc = {
.mask = CLOCKSOURCE_MASK(64),
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#endif
static u64 notrace read_hv_clock_msr(struct clocksource *arg)
{
@ -272,7 +269,6 @@ static struct clocksource hyperv_cs_msr = {
.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};
#ifdef CONFIG_HYPERV_TSCPAGE
static bool __init hv_init_tsc_clocksource(void)
{
u64 tsc_msr;
@ -304,13 +300,6 @@ static bool __init hv_init_tsc_clocksource(void)
return true;
}
#else
static bool __init hv_init_tsc_clocksource(void)
{
return false;
}
#endif
void __init hv_init_clocksource(void)
{

3
drivers/hv/Kconfig
View File

@ -14,9 +14,6 @@ config HYPERV
config HYPERV_TIMER
def_bool HYPERV
config HYPERV_TSCPAGE
def_bool HYPERV && X86_64
config HYPERV_UTILS
tristate "Microsoft Hyper-V Utilities driver"
depends on HYPERV && CONNECTOR && NLS

8
include/clocksource/hyperv_timer.h
View File

@ -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