From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [PATCH v2 13/20] xen/events: fifo: Make it running on 64KB granularity Date: Fri, 24 Jul 2015 11:36:23 +0100 Message-ID: <55B21527.4010601__23555.831021122$1437734290$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> 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 1ZIaLJ-0004v3-Vg for xen-devel@lists.xenproject.org; Fri, 24 Jul 2015 10:36:42 +0000 In-Reply-To: <1436474552-31789-14-git-send-email-julien.grall@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: Julien Grall , xen-devel@lists.xenproject.org Cc: ian.campbell@citrix.com, stefano.stabellini@eu.citrix.com, linux-kernel@vger.kernel.org, Boris Ostrovsky , linux-arm-kernel@lists.infradead.org List-Id: xen-devel@lists.xenproject.org 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 > > 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. David