sched clock callback should return time with nano second as unit
but current hv callback returns time with 100ns. Fix it.
Cc: [email protected]
Signed-off-by: Yubo Xie <[email protected]>
Signed-off-by: Tianyu Lan <[email protected]>
Fixes: adb87ff4f96c ("clocksource/drivers/hyperv: Allocate Hyper-V TSC page statically")
---
drivers/clocksource/hyperv_timer.c | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
index 9d808d595ca8..662ed978fa24 100644
--- a/drivers/clocksource/hyperv_timer.c
+++ b/drivers/clocksource/hyperv_timer.c
@@ -343,7 +343,8 @@ static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
static u64 read_hv_sched_clock_tsc(void)
{
- return read_hv_clock_tsc() - hv_sched_clock_offset;
+ return (read_hv_clock_tsc() - hv_sched_clock_offset)
+ * (NSEC_PER_SEC / HV_CLOCK_HZ);
}
static void suspend_hv_clock_tsc(struct clocksource *arg)
@@ -398,7 +399,8 @@ static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
static u64 read_hv_sched_clock_msr(void)
{
- return read_hv_clock_msr() - hv_sched_clock_offset;
+ return (read_hv_clock_msr() - hv_sched_clock_offset)
+ * (NSEC_PER_SEC / HV_CLOCK_HZ);
}
static struct clocksource hyperv_cs_msr = {
--
2.14.5
Yubo Xie <[email protected]> writes:
> sched clock callback should return time with nano second as unit
> but current hv callback returns time with 100ns. Fix it.
>
> Cc: [email protected]
> Signed-off-by: Yubo Xie <[email protected]>
> Signed-off-by: Tianyu Lan <[email protected]>
> Fixes: adb87ff4f96c ("clocksource/drivers/hyperv: Allocate Hyper-V TSC page statically")
I don't think this is the right commit to reference,
commit bd00cd52d5be655a2f217e2ed74b91a71cb2b14f
Author: Tianyu Lan <[email protected]>
Date: Wed Aug 14 20:32:16 2019 +0800
clocksource/drivers/hyperv: Add Hyper-V specific sched clock function
looks like the one.
> ---
> drivers/clocksource/hyperv_timer.c | 6 ++++--
> 1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
> index 9d808d595ca8..662ed978fa24 100644
> --- a/drivers/clocksource/hyperv_timer.c
> +++ b/drivers/clocksource/hyperv_timer.c
> @@ -343,7 +343,8 @@ static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
>
> static u64 read_hv_sched_clock_tsc(void)
> {
> - return read_hv_clock_tsc() - hv_sched_clock_offset;
> + return (read_hv_clock_tsc() - hv_sched_clock_offset)
> + * (NSEC_PER_SEC / HV_CLOCK_HZ);
> }
>
> static void suspend_hv_clock_tsc(struct clocksource *arg)
> @@ -398,7 +399,8 @@ static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
>
> static u64 read_hv_sched_clock_msr(void)
> {
> - return read_hv_clock_msr() - hv_sched_clock_offset;
> + return (read_hv_clock_msr() - hv_sched_clock_offset)
> + * (NSEC_PER_SEC / HV_CLOCK_HZ);
> }
kvmclock seems to have the same (pre-patch) code ...
>
> static struct clocksource hyperv_cs_msr = {
--
Vitaly
Hi Vitaly:
Thanks for your review.
On 3/24/2020 11:49 PM, Vitaly Kuznetsov wrote:
> Yubo Xie <[email protected]> writes:
>
>> sched clock callback should return time with nano second as unit
>> but current hv callback returns time with 100ns. Fix it.
>>
>> Cc: [email protected]
>> Signed-off-by: Yubo Xie <[email protected]>
>> Signed-off-by: Tianyu Lan <[email protected]>
>> Fixes: adb87ff4f96c ("clocksource/drivers/hyperv: Allocate Hyper-V TSC page statically")
>
> I don't think this is the right commit to reference,
>
> commit bd00cd52d5be655a2f217e2ed74b91a71cb2b14f
> Author: Tianyu Lan <[email protected]>
> Date: Wed Aug 14 20:32:16 2019 +0800
>
> clocksource/drivers/hyperv: Add Hyper-V specific sched clock function
>
> looks like the one.
Sorry. You are right. Will update in the next version.
>
>> ---
>> drivers/clocksource/hyperv_timer.c | 6 ++++--
>> 1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/drivers/clocksource/hyperv_timer.c b/drivers/clocksource/hyperv_timer.c
>> index 9d808d595ca8..662ed978fa24 100644
>> --- a/drivers/clocksource/hyperv_timer.c
>> +++ b/drivers/clocksource/hyperv_timer.c
>> @@ -343,7 +343,8 @@ static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
>>
>> static u64 read_hv_sched_clock_tsc(void)
>> {
>> - return read_hv_clock_tsc() - hv_sched_clock_offset;
>> + return (read_hv_clock_tsc() - hv_sched_clock_offset)
>> + * (NSEC_PER_SEC / HV_CLOCK_HZ);
>> }
>>
>> static void suspend_hv_clock_tsc(struct clocksource *arg)
>> @@ -398,7 +399,8 @@ static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
>>
>> static u64 read_hv_sched_clock_msr(void)
>> {
>> - return read_hv_clock_msr() - hv_sched_clock_offset;
>> + return (read_hv_clock_msr() - hv_sched_clock_offset)
>> + * (NSEC_PER_SEC / HV_CLOCK_HZ);
>> }
>
> kvmclock seems to have the same (pre-patch) code ...
kvm sched clock gets time from pvclock_clocksource_read() and
the time unit is nanosecond. So there is such issue in KVM code.
>
>>
>> static struct clocksource hyperv_cs_msr = {
>
Tianyu Lan <[email protected]> writes:
>>> @@ -398,7 +399,8 @@ static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
>>>
>>> static u64 read_hv_sched_clock_msr(void)
>>> {
>>> - return read_hv_clock_msr() - hv_sched_clock_offset;
>>> + return (read_hv_clock_msr() - hv_sched_clock_offset)
>>> + * (NSEC_PER_SEC / HV_CLOCK_HZ);
>>> }
>>
>> kvmclock seems to have the same (pre-patch) code ...
>
>
> kvm sched clock gets time from pvclock_clocksource_read() and
> the time unit is nanosecond. So there is such issue in KVM code.
>
Ah, true, kvmclock is always 1Ghz so it's reading 'naturally' converts
to ns.
--
Vitaly
> From: [email protected]
> <[email protected]> On Behalf Of Yubo Xie
> Sent: Tuesday, March 24, 2020 8:20 AM
> ...
> sched clock callback should return time with nano second as unit
> but current hv callback returns time with 100ns. Fix it.
Hi Yubo,
I'm curious how you found the bug? :-) Did you notice some kind of symtom?
Thanks,
-- Dexuan
I use "time" to run some performance tests in our project under WSL2, but the result looks weird: the value of "real" is far from the sum of "user" + "sys".
-----Original Message-----
From: Dexuan Cui <[email protected]>
Sent: Wednesday, March 25, 2020 11:46 AM
To: Yubo Xie <[email protected]>; KY Srinivasan <[email protected]>; Haiyang Zhang <[email protected]>; Stephen Hemminger <[email protected]>; Wei Liu <[email protected]>; [email protected]; [email protected]; Michael Kelley <[email protected]>
Cc: Yubo Xie <[email protected]>; [email protected]; [email protected]; vkuznets <[email protected]>; [email protected]; Tianyu Lan <[email protected]>
Subject: RE: [PATCH] x86/Hyper-V: Fix hv sched clock function return wrong time unit
> From: [email protected]
> <[email protected]> On Behalf Of Yubo Xie
> Sent: Tuesday, March 24, 2020 8:20 AM
> ...
> sched clock callback should return time with nano second as unit but
> current hv callback returns time with 100ns. Fix it.
Hi Yubo,
I'm curious how you found the bug? :-) Did you notice some kind of symtom?
Thanks,
-- Dexuan