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From: "Yu, Fenghua" <fenghua.yu@intel.com>
To: "Yu, Fenghua" <fenghua.yu@intel.com>, Andy Lutomirski <luto@kernel.org>
Cc: "Xu, Tao3" <tao3.xu@intel.com>,
	"Liu, Jingqi" <jingqi.liu@intel.com>,
	Thomas Gleixner <tglx@linutronix.de>,
	Borislav Petkov <bp@alien8.de>, "Ingo Molnar" <mingo@redhat.com>,
	H Peter Anvin <hpa@zytor.com>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	"Raj, Ashok" <ashok.raj@intel.com>,
	"Shankar, Ravi V" <ravi.v.shankar@intel.com>,
	linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: RE: [PATCH v2 1/3] x86/cpufeatures: Enumerate user wait instructions
Date: Thu, 21 Feb 2019 22:57:49 +0000	[thread overview]
Message-ID: <3E5A0FA7E9CA944F9D5414FEC6C712209D877F3A@ORSMSX106.amr.corp.intel.com> (raw)
In-Reply-To: <20190221192424.GA158428@romley-ivt3.sc.intel.com>

> From: Fenghua Yu [mailto:fenghua.yu@intel.com]
> On Wed, Feb 20, 2019 at 10:37:27PM -0800, Andy Lutomirski wrote:
> Or to simplify the situation, how about we still use zero as global max wait
> time (i.e. no limitation for global wait time) as implemented in this patch
> set? User can still change the value to any value based on their usage. Isn't
> this a right way to take care of any usage?

Plus, if scheduler timers works, umwait will be forced time out by timer in HZ anyway.

Only for case without scheduler timer, sysadmin may need to set a small max umwait time to force timout. But in this case (real time), I doubt user app really wants to call umwait to save power with long latency of waking up from umwait. So likely in this case, user app won't call umwait and there is no usage to set a small value for max umwait time. 

Thanks.

-Fenghua

  reply	other threads:[~2019-02-21 22:57 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-01-16 21:18 [PATCH v2 0/3] x86/umwait: Enable user wait instructions Fenghua Yu
2019-01-16 21:18 ` [PATCH v2 1/3] x86/cpufeatures: Enumerate " Fenghua Yu
2019-01-16 21:18 ` [PATCH v2 2/3] x86/umwait: Setup umwait C0.2 state Fenghua Yu
2019-01-16 23:51   ` Andy Lutomirski
2019-01-16 21:18 ` [PATCH v2 3/3] x86/umwait: Control umwait maximum time Fenghua Yu
2019-01-17  0:00   ` Andy Lutomirski
2019-01-17  0:07     ` Fenghua Yu
2019-01-17  0:30       ` Andy Lutomirski
2019-01-17  2:06         ` Fenghua Yu
2019-01-20 19:12     ` Andrew Cooper
2019-01-20 21:40       ` Andy Lutomirski
2019-02-08 18:51       ` Yu, Fenghua
2019-01-16 21:18 ` [PATCH v2 0/3] x86/umwait: Enable user wait instructions Fenghua Yu
2019-01-16 21:18 ` [PATCH v2 1/3] x86/cpufeatures: Enumerate " Fenghua Yu
2019-02-21  6:37   ` Andy Lutomirski
2019-02-21  9:22     ` Peter Zijlstra
2019-02-21 19:24     ` Fenghua Yu
2019-02-21 22:57       ` Yu, Fenghua [this message]
2019-02-24 19:45         ` Andy Lutomirski
2019-02-26 19:53           ` Fenghua Yu
2019-02-22  2:09       ` Tao Xu
2019-02-26 20:41     ` Fenghua Yu
2019-01-16 21:18 ` [PATCH v2 2/3] x86/umwait: Setup umwait C0.2 state Fenghua Yu
2019-01-16 21:18 ` [PATCH v2 3/3] x86/umwait: Control umwait maximum time Fenghua Yu

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