From: Vitaly Kuznetsov <vkuznets@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org,
x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
Borislav Petkov <bp@alien8.de>, "H. Peter Anvin" <hpa@zytor.com>,
"K. Y. Srinivasan" <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Sasha Levin <sashal@kernel.org>,
Daniel Lezcano <daniel.lezcano@linaro.org>,
Michael Kelley <mikelley@microsoft.com>,
Tianyu Lan <Tianyu.Lan@microsoft.com>,
Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] x86/hyper-v: enable TSC page clocksource on 32bit
Date: Thu, 22 Aug 2019 09:52:14 +0200 [thread overview]
Message-ID: <877e75r61d.fsf@vitty.brq.redhat.com> (raw)
In-Reply-To: <alpine.DEB.2.21.1908212321320.1983@nanos.tec.linutronix.de>
Thomas Gleixner <tglx@linutronix.de> writes:
> On Wed, 21 Aug 2019, Thomas Gleixner wrote:
>
>> On Wed, 21 Aug 2019, Vitaly Kuznetsov wrote:
>>
>> > 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 (unilizing vDSO in case of TSC page):
>> > MSR based clocksource: 5664 cycles
>> > TSC page clocksource: 131 cycles
>> >
>> > Enabling TSC page on 32bits allows us to get rid of CONFIG_HYPERV_TSCPAGE
>>
>> s/allows us/allows/
>>
>> > as it is now not any different from CONFIG_HYPERV_TIMER.
>> >
>> > Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
>> > ---
>> > arch/x86/include/asm/vdso/gettimeofday.h | 6 +++---
>> > drivers/clocksource/hyperv_timer.c | 11 -----------
>> > drivers/hv/Kconfig | 3 ---
>> > include/clocksource/hyperv_timer.h | 6 ++----
>> > 4 files changed, 5 insertions(+), 21 deletions(-)
>>
>> Really nice cleanup as a side effect of adding functionality.
>
> That said, could you please rebase that on
>
> git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git timers/core
>
> as I just applied the TSC page patches there and this conflicts left and
> right.
Sure, v2 is coming!
--
Vitaly
prev parent reply other threads:[~2019-08-22 7:52 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-21 9:56 [PATCH] x86/hyper-v: enable TSC page clocksource on 32bit Vitaly Kuznetsov
2019-08-21 21:16 ` Michael Kelley
2019-08-21 21:17 ` Thomas Gleixner
2019-08-21 21:23 ` Thomas Gleixner
2019-08-22 7:52 ` Vitaly Kuznetsov [this message]
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=877e75r61d.fsf@vitty.brq.redhat.com \
--to=vkuznets@redhat.com \
--cc=Tianyu.Lan@microsoft.com \
--cc=bp@alien8.de \
--cc=daniel.lezcano@linaro.org \
--cc=haiyangz@microsoft.com \
--cc=hpa@zytor.com \
--cc=kys@microsoft.com \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mikelley@microsoft.com \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
--cc=sashal@kernel.org \
--cc=sthemmin@microsoft.com \
--cc=tglx@linutronix.de \
--cc=x86@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 an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.