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Re: [RFC] Porting string performance tests into benchtests
- From: OndÅej BÃlka <neleai at seznam dot cz>
- To: David Miller <davem at davemloft dot net>
- Cc: siddhesh at redhat dot com, libc-alpha at sourceware dot org
- Date: Thu, 4 Apr 2013 17:55:21 +0200
- Subject: Re: [RFC] Porting string performance tests into benchtests
- References: <20130403101130 dot GE20842 at spoyarek dot pnq dot redhat dot com> <20130403 dot 123522 dot 1616212976811705615 dot davem at davemloft dot net> <20130404033719 dot GA14860 at spoyarek dot pnq dot redhat dot com> <20130403 dot 234042 dot 1776194180184022553 dot davem at davemloft dot net>
On Wed, Apr 03, 2013 at 11:40:42PM -0400, David Miller wrote:
> From: Siddhesh Poyarekar <siddhesh@redhat.com>
> Date: Thu, 4 Apr 2013 09:07:19 +0530
>
> > On Wed, Apr 03, 2013 at 12:35:22PM -0400, David Miller wrote:
> >>
> >> I strongly perfer the raw cpu cycle counter read.
> >
> > Could you elaborate on that? Is it just a personal preference or is
> > some aspect of my argument in favour of clock_gettime incorrect or
> > irrelevant?
>
> I really want to see on the cpu cycle level whether the changes I make
> to the pre-loop and post-loop code make any difference.
>
Which as for str* majority of time is spend on pre/loop code is most
important to measure.
> And on sparc chips I don't have the issues that can make the cpu cycle
> counter inaccurate or less usable as a timing mechanism.
Other benefit is that you can rapidly vary implementations. This mostly
eliminate biases caused by cpu frequency switching etc.