linux-kernel - Re: [PATCH 4/4] trace: profile all if conditionals

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20081123213855.GB16613@elte.hu>
Date:	Sun, 23 Nov 2008 22:38:55 +0100
From:	Ingo Molnar <mingo@...e.hu>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	Andrew Morton <akpm@...ux-foundation.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Peter Zijlstra <peterz@...radead.org>,
	Theodore Tso <tytso@....edu>,
	Arjan van de Ven <arjan@...radead.org>,
	Steven Rostedt <srostedt@...hat.com>
Subject: Re: [PATCH 4/4] trace: profile all if conditionals


* Steven Rostedt <rostedt@...dmis.org> wrote:

> On Sun, 23 Nov 2008, Andi Kleen wrote:
> > Steven Rostedt <rostedt@...dmis.org> writes:
> 
> > > This adds a significant amount of overhead and should only be 
> > > used by those analyzing their system.
> > 
> > Often this can be also done using CPU performance counters. Might 
> > be a cheaper option.
> 
> I'd love to add an option that could hook into any arch with HW 
> support for this. We could dump out the same information, but just a 
> different way to gather it.  But I'm still ignorant to the use of 
> CPU performance counters and how to find which branch matches which 
> if.

there's already new ftrace code for this and the patches are done - 
stay tuned.

but it wont be a replacement for the soft method (which is more 
flexible - the hw can only do 'all or nothing' type of branch 
tracing), so it's complementary.

	Ingo
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/