linux-kernel - Re: [PATCH 4/5] x86: entry_64.S: always allocate complete "struct pt

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Date:	Sat, 02 Aug 2014 14:23:04 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andy Lutomirski <luto@...capital.net>
CC:	Denys Vlasenko <vda.linux@...glemail.com>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
	Oleg Nesterov <oleg@...hat.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	X86 ML <x86@...nel.org>, Alexei Starovoitov <ast@...mgrid.com>,
	Will Drewry <wad@...omium.org>,
	Kees Cook <keescook@...omium.org>
Subject: Re: [PATCH 4/5] x86: entry_64.S: always allocate complete "struct pt_regs"

It would be nice to automate running a T-test on it.

On August 2, 2014 2:14:50 PM PDT, Andy Lutomirski <luto@...capital.net> wrote:
>On Fri, Aug 1, 2014 at 3:13 PM, H. Peter Anvin <hpa@...or.com> wrote:
>> On 08/01/2014 03:11 PM, Denys Vlasenko wrote:
>>>>
>>>> Could you please try to see if there is a measurable change in the
>>>> latency of a trivial syscall?
>>>
>>> Will do.
>>> Something along the lines of "how long does it take to execute two
>>> gazillions of getppid()?"
>>>
>>
>> Something like that, yes, but you have to run enough data points so
>you
>> can determine if the difference is statistically significant or just
>noise.
>
>Denys, if you want to avoid five minutes of programming, you can build
>this:
>
>https://gitorious.org/linux-test-utils/linux-clock-tests/
>
>and run timing_test_64 10 getpid
>
>It doesn't do real statistics, but it seems to get quite stable
>results.
>
>--Andy

-- 
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