linux-kernel - Re: [PATCH v2 7/11] Uprobes Implementation

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Message-ID: <1273609938.1810.81.camel@laptop>
Date:	Tue, 11 May 2010 22:32:18 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Srikar Dronamraju <srikar@...ux.vnet.ibm.com>,
	Ingo Molnar <mingo@...e.hu>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Masami Hiramatsu <mhiramat@...hat.com>,
	Randy Dunlap <rdunlap@...otime.net>,
	Ananth N Mavinakayanahalli <ananth@...ibm.com>,
	Jim Keniston <jkenisto@...ux.vnet.ibm.com>,
	Frederic Weisbecker <fweisbec@...il.com>,
	"Frank Ch. Eigler" <fche@...hat.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Roland McGrath <roland@...hat.com>
Subject: Re: [PATCH v2 7/11] Uprobes Implementation

On Tue, 2010-04-20 at 17:30 +0200, Oleg Nesterov wrote:
> > >     - I don't really understand why ->handler_in_interrupt is really
> > >       useful, but never mind.
> >
> > There is a small overhead when running the handlers in task context.
> 
> Sure, but
> 
> > overhead of task over interrupt =  (1.016851 - .907400) = .109451 usec
> > % additional overhead = (.109451/.907400) * 100 = 12.062%
> 
> this overhead looks very minor. To me, it is better to simplify the
> code, at least in the first version.
> 
> That said, this is up to you, I am not asking you to remove this
> optimization. Just imho. 

Right so what I've suggested several times it to simply call the same
handler in both contexts. If it returns -EFAULT, set TIF_UPROBE or
whatever and try again from task context.



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