From: Oliver Mangold Subject: Re: Poor RNG performance on Ryzen Date: Fri, 21 Jul 2017 16:55:12 +0200 Message-ID: References: <1218e9b7-4eeb-d8a0-02b2-8ddd672ec454@gmail.com> <20170721092656.GA18604@wintermute> <09c9be2b-8b4d-ee06-8071-4f748fdb5970@gmail.com> <20170721144741.4igkvsd2fowptsy2@thunk.org> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit To: linux-crypto@vger.kernel.org Return-path: Received: from mail-wm0-f51.google.com ([74.125.82.51]:37610 "EHLO mail-wm0-f51.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754533AbdGUOzP (ORCPT ); Fri, 21 Jul 2017 10:55:15 -0400 Received: by mail-wm0-f51.google.com with SMTP id e131so16278179wme.0 for ; Fri, 21 Jul 2017 07:55:15 -0700 (PDT) Received: from laptop-olli.localdomain ([2a02:8070:7b0:ed00:a81a:6d6:cddf:9db4]) by smtp.googlemail.com with ESMTPSA id r128sm1423949wmb.27.2017.07.21.07.55.13 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 21 Jul 2017 07:55:13 -0700 (PDT) In-Reply-To: <20170721144741.4igkvsd2fowptsy2@thunk.org> Sender: linux-crypto-owner@vger.kernel.org List-ID: On 21.07.2017 16:47, Theodore Ts'o wrote: > On Fri, Jul 21, 2017 at 01:39:13PM +0200, Oliver Mangold wrote: >> Better, but obviously there is still much room for improvement by reducing >> the number of calls to RDRAND. > Hmm, is there some way we can easily tell we are running on Ryzen? Or > do we believe this is going to be true for all AMD devices? I would like to note that my first measurement on Broadwell suggest that the current frequency of RDRAND calls seems to slow things down on Intel also (but not as much as on Ryzen).