From: Daniel Lezcano <daniel.lezcano@linaro.org>
To: "Michael Kelley (LINUX)" <mikelley@microsoft.com>,
KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
"wei.liu@kernel.org" <wei.liu@kernel.org>,
Dexuan Cui <decui@microsoft.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>
Subject: Re: [PATCH 1/1] clocksource: hyper-v: Rework clocksource and sched clock setup
Date: Mon, 19 Jun 2023 18:58:24 +0200 [thread overview]
Message-ID: <07c5efe5-4eb0-121f-7b50-8f3fba68beab@linaro.org> (raw)
In-Reply-To: <BYAPR21MB1688E1163BB36DF03CC8E00BD75FA@BYAPR21MB1688.namprd21.prod.outlook.com>
On 19/06/2023 18:44, Michael Kelley (LINUX) wrote:
> From: Daniel Lezcano <daniel.lezcano@linaro.org> Sent: Monday, June 19, 2023 9:16 AM
>>
>> On 09/06/2023 17:47, Michael Kelley wrote:
>>> Current code assigns either the Hyper-V TSC page or MSR-based ref counter
>>> as the sched clock. This may be sub-optimal in two cases. First, if there
>>> is hardware support to ensure consistent TSC frequency across live
>>> migrations and Hyper-V is using that support, the raw TSC is a faster
>>> source of time than the Hyper-V TSC page. Second, the MSR-based ref
>>> counter is relatively slow because reads require a trap to the hypervisor.
>>> As such, it should never be used as the sched clock. The native sched
>>> clock based on the raw TSC or jiffies is much better.
>>>
>>> Rework the sched clock setup so it is set to the TSC page only if
>>> Hyper-V indicates that the TSC may have inconsistent frequency across
>>> live migrations. Also, remove the code that sets the sched clock to
>>> the MSR-based ref counter. In the cases where it is not set, the sched
>>> clock will then be the native sched clock.
>>>
>>> As part of the rework, always enable both the TSC page clocksource and
>>> the MSR-based ref counter clocksource. Set the ratings so the TSC page
>>> clocksource is preferred. While the MSR-based ref counter clocksource
>>> is unlikely to ever be the default, having it available for manual
>>> selection is convenient for development purposes.
>>>
>>> Signed-off-by: Michael Kelley <mikelley@microsoft.com>
>>
>> The patch does not apply, does it depend on another patch?
>
> It should apply to linux-next. It depends on two previous patches from
> Peter Zijlstra in the sched/core branch of tip. See:
>
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=sched/core&id=9397fa2ea3e7634f61da1ab76b9eb88ba04dfdfc
>
> and
>
> https://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git/commit/?h=sched/core&id=e39acc37db34f6688e2c16e958fb1d662c422c81
Yeah, but the branch is tip/timers/core
Could you respin against it ?
Thanks
--
<http://www.linaro.org/> Linaro.org │ Open source software for ARM SoCs
Follow Linaro: <http://www.facebook.com/pages/Linaro> Facebook |
<http://twitter.com/#!/linaroorg> Twitter |
<http://www.linaro.org/linaro-blog/> Blog
next prev parent reply other threads:[~2023-06-19 16:59 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-06-09 15:47 [PATCH 1/1] clocksource: hyper-v: Rework clocksource and sched clock setup Michael Kelley
2023-06-15 5:15 ` Dexuan Cui
2023-06-19 16:16 ` Daniel Lezcano
2023-06-19 16:44 ` Michael Kelley (LINUX)
2023-06-19 16:58 ` Daniel Lezcano [this message]
2023-06-19 17:41 ` Michael Kelley (LINUX)
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=07c5efe5-4eb0-121f-7b50-8f3fba68beab@linaro.org \
--to=daniel.lezcano@linaro.org \
--cc=decui@microsoft.com \
--cc=haiyangz@microsoft.com \
--cc=kys@microsoft.com \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mikelley@microsoft.com \
--cc=tglx@linutronix.de \
--cc=wei.liu@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).