From: "H. Peter Anvin" <hpa@zytor.com>
To: Andy Lutomirski <luto@amacapital.net>,
"Yu, Fenghua" <fenghua.yu@intel.com>
Cc: Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
"Mallick, Asit K" <asit.k.mallick@intel.com>,
linux-kernel <linux-kernel@vger.kernel.org>, x86 <x86@kernel.org>
Subject: Re: [PATCH 0/15] x86/xsaves: Optimize xstate context switch by xsaves/xrstors
Date: Mon, 26 May 2014 14:47:11 -0700 [thread overview]
Message-ID: <5383B65F.6030602@zytor.com> (raw)
In-Reply-To: <CALCETrUyVBfWkhckAo0STtY_Sq4OGXw5-c8f_w_ZKQxSWxTCvA@mail.gmail.com>
On 05/26/2014 02:40 PM, Andy Lutomirski wrote:
>>>
>>> Are we going to want to encourage userspace to do something like
>>> sticking vzeroupper right before each syscall to make any
>>> xsaves/xrestores faster?
>>
>> This patch set allow compacted format in kernel and standard format
>> in user space. This works fine for both kernel and user application.
>
> My question is purely about optimization: if userspace does a blocking
> system call, will it be significantly faster if userspace zeros out as
> much of the extended state as possible before doing the system call?
>
> I think I tried this once with xsaveopt and decided that it didn't
> make much of a difference.
>
XSAVEOPT and XSAVES would be the same in this case. Keep in mind, too,
that relatively few system calls result in context switches, which is
the only time this ends up mattering.
-hpa
prev parent reply other threads:[~2014-05-26 21:47 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-05-26 17:01 [PATCH 0/15] x86/xsaves: Optimize xstate context switch by xsaves/xrstors Fenghua Yu
2014-05-26 17:01 ` [PATCH 01/15] x86/xsaves: Detect xsaves/xrstors feature Fenghua Yu
2014-05-26 17:01 ` [PATCH 02/15] x86/xsaves: Add kernel parameter to disable xsaves/xrstors Fenghua Yu
2014-05-26 17:01 ` [PATCH 03/15] x86/alternative: Add alternative_input_2 Fenghua Yu
2014-05-26 17:01 ` [PATCH 04/15] x86/xsaves: Change compacted format xsave area header Fenghua Yu
2014-05-26 17:01 ` [PATCH 05/15] x86/xsaves: Define macros for xsave instructions Fenghua Yu
2014-05-26 17:01 ` [PATCH 06/15] x86/xsaves: Define macro for handle xsave/xrstor fault Fenghua Yu
2014-05-26 17:01 ` [PATCH 07/15] x86/xsaves: Use xsaves/xrstors for saving and restoring xsave area Fenghua Yu
2014-05-26 17:01 ` [PATCH 08/15] x86/xsaves: Use xsaves/xrstors for context switch Fenghua Yu
2014-05-26 17:01 ` [PATCH 09/15] x86/xsaves: Use xsave/xrstor for saving and restoring user space context Fenghua Yu
2014-05-26 17:01 ` [PATCH 10/15] x86/xsaves: Clear reserved bits in xsave header Fenghua Yu
2014-05-26 17:01 ` [PATCH 11/15] x86/xsaves: Add xsaves and xrstors support for booting time Fenghua Yu
2014-05-26 17:01 ` [PATCH 12/15] x86/xsaves: Save xstate to task's xsave area in __save_fpu during " Fenghua Yu
2014-05-26 17:01 ` [PATCH 13/15] x86/xsaves: Call booting time xsaves and xrstors in setup_init_fpu_buf Fenghua Yu
2014-05-26 17:01 ` [PATCH 14/15] x86/xsaves: Enable xsaves/xrstors Fenghua Yu
2014-05-26 17:01 ` [PATCH 15/15] Define kernel API to get address of each state in xsave area Fenghua Yu
2014-05-26 19:37 ` [PATCH 0/15] x86/xsaves: Optimize xstate context switch by xsaves/xrstors Andy Lutomirski
2014-05-26 20:13 ` Yu, Fenghua
2014-05-26 20:53 ` H. Peter Anvin
2014-05-26 21:40 ` Andy Lutomirski
2014-05-26 21:47 ` H. Peter Anvin [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=5383B65F.6030602@zytor.com \
--to=hpa@zytor.com \
--cc=asit.k.mallick@intel.com \
--cc=fenghua.yu@intel.com \
--cc=linux-kernel@vger.kernel.org \
--cc=luto@amacapital.net \
--cc=mingo@elte.hu \
--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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox