linux-kernel - Re: [PATCH] x86, perf: Use INST_RETIRED.PREC

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: <20151021165542.GN3533@two.firstfloor.org>
Date:	Wed, 21 Oct 2015 18:55:42 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Peter Zijlstra <peterz@...radead.org>
Cc:	Andi Kleen <ak@...ux.intel.com>, Andi Kleen <andi@...stfloor.org>,
	linux-kernel@...r.kernel.org, Ingo Molnar <mingo@...nel.org>,
	Thomas Gleixner <tglx@...utronix.de>
Subject: Re: [PATCH] x86, perf: Use INST_RETIRED.PREC_DIST for cycles:pp on
 Skylake

On Wed, Oct 21, 2015 at 06:52:52PM +0200, Peter Zijlstra wrote:
> On Wed, Oct 21, 2015 at 08:26:08AM -0700, Andi Kleen wrote:
> > So it turns out that UOPS_RETIRED.ALL+pebs only works by accident
> > on Skylake. It's not in the specification.
> 
> Accident or not, it works and you've tested it. Might as well keep it.
> Specs can be updated.

No, it's better not to use it.

> Also, even with the SNB 'hickup' they still haven't got the memo that
> cycles is important for PEBS ?

INST_RETIRED.PREC_DIST is a far better cycles than UOPS_RETIRED.ALL
(see my earlier example)

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
--
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/