netdev - Re: Receive side performance issue with multi-10-GigE and NUMA

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Date:	Wed, 26 Aug 2009 16:23:44 -0400
From:	Neil Horman <nhorman@...driver.com>
To:	Ingo Molnar <mingo@...e.hu>
Cc:	David Miller <davem@...emloft.net>, rostedt@...dmis.org,
	fweisbec@...il.com, billfink@...dspring.com,
	netdev@...r.kernel.org, brice@...i.com, gallatin@...i.com
Subject: Re: Receive side performance issue with multi-10-GigE and NUMA

On Wed, Aug 26, 2009 at 09:48:35PM +0200, Ingo Molnar wrote:
> 
> * David Miller <davem@...emloft.net> wrote:
> 
> > From: Ingo Molnar <mingo@...e.hu>
> > Date: Wed, 26 Aug 2009 21:08:30 +0200
> > 
> > > Sigh, no. Please re-read the past discussions about this. 
> > > trace_skb_sources.c is a hack and should be converted to generic 
> > > tracepoints. Is there anything in it that cannot be expressed in 
> > > terms of TRACE_EVENT()?
> > 
> > Neil explained why he needed to implement it this way in his reply 
> > to Steven Rostedt.  I attach it here for your convenience.
> 
> thanks. The argument is invalid:
> 
Just because you assert that doesn't make it so, Ingo.

> > > BTW, why not just do this as events? Or was this just a easy way 
> > > to communicate with the user space tools?
> > 
> > Thats exactly why I did it.  the idea is for me to now write a 
> > user space tool that lets me analyze the events and ajust process 
> > scheduling to optimize the rx path. Neil
> 
> All tooling (in fact _more_ tooling) can be done based on generic, 
> TRACE_EVENT() based tracepoints. Generic tracepoints are far more 
> available, have a generalized format with format parsers and user 
> tooling implemented, etc. etc.
> 
Then why allow for ftrace modules at all?  I grant that the skb ftracer is a bit
trivial at the moment for an ftrace module, but I really prefer to leave it is
so that I can expand it with additional tracepoints.  And looking at them,
anything you've said above applies to any of the currently implemented ftrace
modules.  If you're so adamant that we should just do everything with
TRACE_EVENT log messages, then lets get rid of the ftrace infrastructure all
together.  Until we do that, however, I like my skb tracer just as it is.

Neil

> 	Ingo
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