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Date:      Thu, 25 Apr 2013 11:28:15 +0200
From:      Andre Oppermann <andre@freebsd.org>
To:        =?ISO-8859-1?Q?Olivier_Cochard-Labb=E9?= <olivier@cochard.me>
Cc:        "freebsd-net@freebsd.org" <freebsd-net@freebsd.org>, "freebsd-current@freebsd.org" <freebsd-current@freebsd.org>, Sami Halabi <sodynet1@gmail.com>
Subject:   Re: forwarding/ipfw/pf evolution (in pps) on -current
Message-ID:  <5178F72F.90008@freebsd.org>
In-Reply-To: <CA%2Bq%2BTcpRZ_Dc=WTE522zWZ54VviaoQPsRT8%2BgWM%2BoRk5nUpOkg@mail.gmail.com>
References:  <CA%2Bq%2BTcpghAtae7%2BuXehxP9%2BtNh1TiTzxOShDNkLt_xSrgoBGdA@mail.gmail.com> <CAEW%2BogY%2BOmtqS7S1OOHXL8LnYSur5nfpJnvi=aM6vjCKH124Hw@mail.gmail.com> <CA%2Bq%2BTcpRZ_Dc=WTE522zWZ54VviaoQPsRT8%2BgWM%2BoRk5nUpOkg@mail.gmail.com>

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On 25.04.2013 07:40, Olivier Cochard-Labbé wrote:
> On Wed, Apr 24, 2013 at 1:46 PM, Sami Halabi <sodynet1@gmail.com> wrote:
>> 3. there some point of improved performance (without fw) that went down
>> again somewhere before Clang got prod.
>
> Found it !
>
> It's commit 242402: "Rework the known mutexes..."

Again one has to be really careful drawing any firm conclusions from this
as it was measured on a Pentium4 and UP kernel (GENERIC would add WITNESS
and INVARIANT overhead as well).

The Pentium4 is about the worst micro-architecture when it comes to locks
and easily regresses.  At the same time modern Intel Core i[3-7] and AMD64
may actually improve with these changes.  Unless more recent micro-archs
have been shown to exhibit the same regression we can't claim this change
was bad (other than for Pentium4).

-- 
Andre

> ministat -s 242401.forwarding 242402.forwarding
> x 242401.forwarding
> + 242402.forwarding
> +---------------------------------------------------------------------------------------+
> |            +
>                   |
> |+ +      +  +
>     x     xx   x x|
> |
>       |____A____| |
> | |_____A_M___|
>                   |
> +---------------------------------------------------------------------------------------+
>      N           Min           Max        Median           Avg        Stddev
> x   5        417527        420242        418902        419074     1049.7974
> +   5        402211        404828        404096        403689     1237.6696
> Difference at 95.0% confidence
>          -15385 +/- 1673.69
>          -3.67119% +/- 0.399377%
>          (Student's t, pooled s = 1147.58)
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