netdev - Re: [PATCH] rps: make distributing packets fairly among all the online CPUs default

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Message-ID: <412e6f7f1003230458o459b9e45i7327c5330c43e152@mail.gmail.com>
Date:	Tue, 23 Mar 2010 19:58:16 +0800
From:	Changli Gao <xiaosuo@...il.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Tom Herbert <therbert@...gle.com>, netdev@...r.kernel.org,
	Ben Hutchings <bhutchings@...arflare.com>
Subject: Re: [PATCH] rps: make distributing packets fairly among all the 
	online CPUs default

On Tue, Mar 23, 2010 at 7:38 PM, Eric Dumazet <eric.dumazet@...il.com> wrote:
> Le mardi 23 mars 2010 à 18:03 +0800, Changli Gao a écrit :
>
>
> I know _many_ applications that perform better when all network IRQS are
> directed to one CPU only. Single threaded UDP server for example, with
> fast answer, or routers, or ...

Yea, single threaded applicatons can't get much from RPS, but
multi-threaded applications such as apache do. And more and more
applications are programmed with the assumption there are more than
one CPUs/Cores.

>
> Many sysadmins tuned their machine to meet this requirement. Installing
> 2.6.35, if RPS enabled by default will make them unhappy, especially if
> CONFIG_SYSFS is not set, since they wont be able to change RPS settings.
>
> If RPS was good for all workloads, activating it would make sense, but
> this is not the case.
>

The sysadmins you mentioned above are Linux experters, and they know
how to tunning the system to get the best performance, but the default
configuration should be for the ordinary users, who don't know Linux
much.

-- 
Regards，
Changli Gao(xiaosuo@...il.com)
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