linux-kernel - Re: [PATCH net-next 1/2] net: remove NET_LL_RX

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Message-ID: <20130612190103.1545e310@nehalam.linuxnetplumber.net>
Date:	Wed, 12 Jun 2013 19:01:03 -0700
From:	Stephen Hemminger <stephen@...workplumber.org>
To:	David Miller <davem@...emloft.net>
Cc:	eliezer.tamir@...ux.intel.com, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, jesse.brandeburg@...el.com,
	donald.c.skidmore@...el.com, e1000-devel@...ts.sourceforge.net,
	willemb@...gle.com, erdnetdev@...il.com, bhutchings@...arflare.com,
	andi@...stfloor.org, hpa@...or.com, eilong@...adcom.com,
	or.gerlitz@...il.com, amirv@...lanox.com, eliezer@...ir.org.il
Subject: Re: [PATCH net-next 1/2] net: remove NET_LL_RX_POLL config menue

On Wed, 12 Jun 2013 15:12:05 -0700 (PDT)
David Miller <davem@...emloft.net> wrote:

> From: Eliezer Tamir <eliezer.tamir@...ux.intel.com>
> Date: Tue, 11 Jun 2013 17:24:28 +0300
> 
> >  	depends on X86_TSC
> 
> Wait a second, I didn't notice this before.  There needs to be a better
> way to test for the accuracy you need, or if the issue is lack of a proper
> API for cycle counter reading, fix that rather than add ugly arch
> specific dependencies to generic networking code.

This should be sched_clock(), rather than direct TSC access.
Also any code using TSC or sched_clock has to be carefully audited to deal with
clocks running at different rates on different CPU's. Basically value is only
meaning full on same CPU.


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