linux-kernel - Re: [RFC] [PATCH 0/2] x86: make jump labels use int3-based breakpoint instead of stop

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Message-ID: <alpine.LNX.2.00.1307112122020.29788@pobox.suse.cz>
Date:	Thu, 11 Jul 2013 21:23:20 +0200 (CEST)
From:	Jiri Kosina <jkosina@...e.cz>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Jason Baron <jbaron@...mai.com>,
	Masami Hiramatsu <masami.hiramatsu.pt@...achi.com>,
	"H. Peter Anvin" <hpa@...ux.intel.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	mathieu.desnoyers@...icios.com
Subject: Re: [RFC] [PATCH 0/2] x86: make jump labels use int3-based breakpoint
 instead of stop_machine()

On Thu, 11 Jul 2013, Steven Rostedt wrote:

> On Thu, 2013-07-11 at 02:04 +0200, Jiri Kosina wrote:
> 
> > I even have preliminary (completely untested) patch, but would like to 
> > have this merged/acked in the first round before proceeding with porting 
> > ftrace to the new interface.
> > 
> > > Also, I wonder if its worth batching up updates. For example, right now 
> > > we simply update each call-site one at a time even if its associated 
> > > with the same control variable.
> > 
> > That does seem to make sense indeed, but it's not really closely tied to 
> > this patchset, is it?
> 
> If you want to have ftrace use this interface, then we need to support
> batch processing. And you will need to do it with an iterator as well.
> We can not allocate 30,000 locations to run this on. Ftrace has its own
> table, and uses the ftrace iterator to traverse it.
> 
> Thus you would need to do something like:

Yup, I have been looking at the ftrace implementation and came to this 
conclusion; thanks for confirmation.
That's exactly why I wanted to postpone converting ftrace before agreement 
on text_poke_bp() is reached and jump labels are converted.

Thanks,

-- 
Jiri Kosina
SUSE Labs
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