linux-kernel - RE: [PATCH] x86/Hyper-V: Fix hv sched clock function return wrong time unit

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Message-ID: <DM5PR00MB0424FA0EC96382D3B6D2D269B4CE0@DM5PR00MB0424.namprd00.prod.outlook.com>
Date:   Wed, 25 Mar 2020 18:57:14 +0000
From:   Yubo Xie <yuboxie@...rosoft.com>
To:     Dexuan Cui <decui@...rosoft.com>, Yubo Xie <ltykernel@...il.com>,
        KY Srinivasan <kys@...rosoft.com>,
        Haiyang Zhang <haiyangz@...rosoft.com>,
        Stephen Hemminger <sthemmin@...rosoft.com>,
        Wei Liu <liuwe@...rosoft.com>,
        "daniel.lezcano@...aro.org" <daniel.lezcano@...aro.org>,
        "tglx@...utronix.de" <tglx@...utronix.de>,
        Michael Kelley <mikelley@...rosoft.com>
CC:     "linux-hyperv@...r.kernel.org" <linux-hyperv@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        vkuznets <vkuznets@...hat.com>,
        "stable@...r.kernel.org" <stable@...r.kernel.org>,
        Tianyu Lan <Tianyu.Lan@...rosoft.com>
Subject: RE: [PATCH] x86/Hyper-V: Fix hv sched clock function return wrong
 time unit

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 <decui@...rosoft.com> 
Sent: Wednesday, March 25, 2020 11:46 AM
To: Yubo Xie <ltykernel@...il.com>; KY Srinivasan <kys@...rosoft.com>; Haiyang Zhang <haiyangz@...rosoft.com>; Stephen Hemminger <sthemmin@...rosoft.com>; Wei Liu <liuwe@...rosoft.com>; daniel.lezcano@...aro.org; tglx@...utronix.de; Michael Kelley <mikelley@...rosoft.com>
Cc: Yubo Xie <yuboxie@...rosoft.com>; linux-hyperv@...r.kernel.org; linux-kernel@...r.kernel.org; vkuznets <vkuznets@...hat.com>; stable@...r.kernel.org; Tianyu Lan <Tianyu.Lan@...rosoft.com>
Subject: RE: [PATCH] x86/Hyper-V: Fix hv sched clock function return wrong time unit

> From: linux-hyperv-owner@...r.kernel.org
> <linux-hyperv-owner@...r.kernel.org> 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