From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Vrabel Subject: Re: [RFC PATCH V4 11/18] Bump EVTCHNS_PER_BUCKET to 512 Date: Fri, 15 Mar 2013 18:43:21 +0000 Message-ID: <51436BC9.7000108@citrix.com> References: <1362486640-14707-1-git-send-email-wei.liu2@citrix.com> <1362486640-14707-12-git-send-email-wei.liu2@citrix.com> <5143653A.7080406@citrix.com> <1363372620.29093.185.camel@zion.uk.xensource.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1363372620.29093.185.camel@zion.uk.xensource.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: Wei Liu Cc: "Keir (Xen.org)" , Ian Campbell , "jbeulich@suse.com" , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 15/03/13 18:37, Wei Liu wrote: > On Fri, 2013-03-15 at 18:15 +0000, David Vrabel wrote: >> On 05/03/13 12:30, Wei Liu wrote: >>> For 64 bit build and 3-level event channel and the original value of >>> EVTCHNS_PER_BUCKET (128), the space needed to accommodate d->evtchn would be 4 >>> pages (PAGE_SIZE = 4096). Given that not every domain needs 3-level event >>> channel, this leads to waste of memory. Having EVTCHN_PER_BUCKETS to be 512 >>> can occupy exact one page. >> >> This makes the list of buckets a page in size but each bucket is now 4 >> pages. >> > > I'm confused. 3 pages (not 4) with flask, 2 pages without. > On 64 bit w/ FLASK enabled, sizeof(struct evtchn) = 18B, bucket size = > 9216B = 2.25 pages; w/o FLASK enabled, sizeof(struct evtchn) = 10B, > bucket size = 5120B = 1.25 pages. struct evtchn isn't packed so it is 24 bytes with flask and 16 without. David