From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v2] Xen: Spread boot time page scrubbing across all available CPU's Date: Mon, 30 Sep 2013 16:42:56 +0100 Message-ID: <52499C00.9070905@citrix.com> References: <5249981902000078000F80F2@nat28.tlf.novell.com> <52498320.7080405@citrix.com> <5249B66102000078000F81CA@nat28.tlf.novell.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta5.messagelabs.com ([195.245.231.135]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1VQfcv-0003QD-Io for xen-devel@lists.xenproject.org; Mon, 30 Sep 2013 15:43:13 +0000 In-Reply-To: <5249B66102000078000F81CA@nat28.tlf.novell.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Jan Beulich Cc: xen-devel , Malcolm Crossley , tim@xen.org, keir@xen.org List-Id: xen-devel@lists.xenproject.org On 30/09/13 16:35, Jan Beulich wrote: >>>> On 30.09.13 at 15:56, Malcolm Crossley wrote: >> The difference between 1 core per node bandwidth and 3 core's per node >> bandwidth is: >> >> AMD: 30000MB/s (1-core) vs 48000MB/s (3-core) >> Intel: 12000MB/s (1-core) vs 38000MB/s (3-core) >> >> So I think it's worth the extra complexity to have multiple core's per >> node scrubbing memory. > The numbers are convincing. Which means that the only request > I'd have is to avoid more than one hyperthread on a core to get > picked for doing the scrubbing. > > Jan > Why? Being independent operations, scrubbing like this will still be sped up by hyperthreading. As scrubbing RAM is simply a race to get it done as quickly as possible, unless it can be demonstrated that using all cores is actively detrimental to the overall time taken, we really should use all cores where possible. ~Andrew