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 /drivers/clocksource | |
| parent | clocksource/drivers/hyperv: Add Hyper-V specific sched clock function (diff) | |
| download | linux-dev-3e2d94535adb2df15f3907e4b4c7cd8a5a4c2b5a.tar.xz linux-dev-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 'drivers/clocksource')
| -rw-r--r-- | drivers/clocksource/hyperv_timer.c | 11 |
1 files changed, 0 insertions, 11 deletions
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c index c322ab4d3689..2317d4e3daaf 100644 --- a/drivers/clocksource/hyperv_timer.c +++ b/drivers/clocksource/hyperv_timer.c @@ -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) { |