From mboxrd@z Thu Jan 1 00:00:00 1970 From: Julien Grall Subject: Re: [PATCH v2 13/20] xen/events: fifo: Make it running on 64KB granularity Date: Thu, 6 Aug 2015 16:43:15 +0100 Message-ID: <55C38093.8080609__38668.2896213189$1438875983$gmane$org@citrix.com> References: <1436474552-31789-1-git-send-email-julien.grall@citrix.com> <1436474552-31789-14-git-send-email-julien.grall@citrix.com> <55B21527.4010601@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Received: from mail6.bemta14.messagelabs.com ([193.109.254.103]) by lists.xen.org with esmtp (Exim 4.72) (envelope-from ) id 1ZNNLa-0006a2-8e for xen-devel@lists.xenproject.org; Thu, 06 Aug 2015 15:44:46 +0000 In-Reply-To: <55B21527.4010601@citrix.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: David Vrabel , xen-devel@lists.xenproject.org Cc: linux-kernel@vger.kernel.org, Boris Ostrovsky , ian.campbell@citrix.com, linux-arm-kernel@lists.infradead.org, stefano.stabellini@eu.citrix.com List-Id: xen-devel@lists.xenproject.org Hi David, On 24/07/15 11:36, David Vrabel wrote: > On 09/07/15 21:42, Julien Grall wrote: >> Only use the first 4KB of the page to store the events channel info. It >> means that we will wast 60KB every time we allocate page for: >> * control block: a page is allocating per CPU >> * event array: a page is allocating everytime we need to expand it > > Reviewed-by: David Vrabel Thank you! >> >> I think we can reduce the memory waste for the 2 areas by: >> >> * control block: sharing between multiple vCPUs. Although it will >> require some bookkeeping in order to not free the page when the CPU >> goes offline and the other CPUs sharing the page still there >> >> * event array: always extend the array event by 64K (i.e 16 4K >> chunk). That would require more care when we fail to expand the >> event channel. > > I would extend it by 4 KiB each time but only allocate a new page every > 16 times. This minimizes the resources used in Xen. I will keep it in mind when I will send a patch to reduce memory waster. Regards, -- Julien Grall