From: Stephan Mueller Subject: Re: random(4) changes Date: Mon, 25 Apr 2016 19:56:17 +0200 Message-ID: <7735834.PWhNOHfhKX@positron.chronox.de> References: <31776489.IE3eGLxohC@positron.chronox.de> <20160425173825.GB13997@two.firstfloor.org> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Cc: Sandy Harris , LKML , linux-crypto@vger.kernel.org, Theodore Ts'o , Jason Cooper , John Denker , "H. Peter Anvin" To: Andi Kleen Return-path: Received: from mail.eperm.de ([89.247.134.16]:53596 "EHLO mail.eperm.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932791AbcDYR4V (ORCPT ); Mon, 25 Apr 2016 13:56:21 -0400 In-Reply-To: <20160425173825.GB13997@two.firstfloor.org> Sender: linux-crypto-owner@vger.kernel.org List-ID: Am Montag, 25. April 2016, 10:38:25 schrieb Andi Kleen: Hi Andi, > On Mon, Apr 25, 2016 at 07:25:55PM +0200, Stephan Mueller wrote: > > Am Montag, 25. April 2016, 09:06:03 schrieb Andi Kleen: > > > > Hi Andi, > > > > > Sandy Harris writes: > > > > > > There is also the third problem of horrible scalability of /dev/random > > > output on larger systems, for which patches are getting ignored. > > > > > > https://lkml.org/lkml/2016/2/10/716 > > > > > > Ignoring problems does not make them go away. > > > > I have seen your patches, but I am not fully sure I understand the root > > cause. is the noise source handling the issue or the random number > > generation the issue? > > Noise source handling is fine, the problem is the global locking on the > entropy pools when generating random numbers. > > > If it is the latter, can you explain where the scalability issue comes in? > > A single pool which is locked/written to does not scale. Larger systems > need multiple pools That would imply that even when you have a system with 1000 CPUs, you want to have a large amount of random numbers. Is this the use case? Or is simply the presence of 1000 CPUs an issue for "normal" loads on /dev/urandom? > > -Andi Ciao Stephan