From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: [PATCH v6 1/5] sysctl: Make XEN_SYSCTL_numainfo a little more efficient Date: Tue, 7 Apr 2015 17:04:03 +0100 Message-ID: <5523FFF3.8050106@citrix.com> References: <1428358329-8466-1-git-send-email-boris.ostrovsky@oracle.com> <1428358329-8466-2-git-send-email-boris.ostrovsky@oracle.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <1428358329-8466-2-git-send-email-boris.ostrovsky@oracle.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: Boris Ostrovsky , ian.jackson@eu.citrix.com, ian.campbell@citrix.com, wei.liu2@citrix.com, stefano.stabellini@eu.citrix.com, dgdegra@tycho.nsa.gov, jbeulich@suse.com, keir@xen.org Cc: elena.ufimtseva@oracle.com, dario.faggioli@citrix.com, xen-devel@lists.xen.org List-Id: xen-devel@lists.xenproject.org On 06/04/15 23:12, Boris Ostrovsky wrote: > A number of changes to XEN_SYSCTL_numainfo interface: > > * Make sysctl NUMA topology query use fewer copies by combining some > fields into a single structure and copying distances for each node > in a single copy. > * NULL meminfo and distance handles are a request for maximum number > of nodes (num_nodes). If those handles are valid and num_nodes is > is smaller than the number of nodes in the system then -ENOBUFS is > returned (and correct num_nodes is provided) > * Instead of using max_node_index for passing number of nodes keep this > value in num_nodes: almost all uses of max_node_index required adding > or subtracting one to eventually get to number of nodes anyway. > * Replace INVALID_NUMAINFO_ID with XEN_INVALID_MEM_SZ and add > XEN_INVALID_NODE_DIST. > > Signed-off-by: Boris Ostrovsky > Acked-by: Ian Campbell This subtly changes the behaviour of XEN_SYSCTL_numainfo with regards to NULL guest handles. Previously, a caller was able to select which information they wanted by choosing which guest handles were non-NULL. With the new semantics, the caller must pass both ni->meminfo and ni->distance to get either bit of information. Each copy_to_guest_offset() should be gated on a !guest_handle_is_null() so a caller can request meminfo information without distance information. ~Andrew