From mboxrd@z Thu Jan 1 00:00:00 1970 From: Pankaj Gupta Subject: Re: [RFC 2/4] tuntap: Publish tuntap maximum number of queues as module_param Date: Tue, 26 Aug 2014 11:30:48 -0400 (EDT) Message-ID: <1505182754.28731957.1409067048371.JavaMail.zimbra@redhat.com> References: <1408369040-1216-1-git-send-email-pagupta@redhat.com> <1408369040-1216-3-git-send-email-pagupta@redhat.com> <20140820105817.GB1916@nanopsycho.orion> <20140820111724.GE17371@redhat.com> <53F575F8.7000208@redhat.com> <175719847.27217377.1408708342392.JavaMail.zimbra@redhat.com> <20140824111421.GC9561@redhat.com> <53FAA607.3060307@redhat.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: "Michael S. Tsirkin" , Jiri Pirko , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, davem@davemloft.net, dgibson@redhat.com, vfalico@gmail.com, edumazet@google.com, vyasevic@redhat.com, hkchu@google.com, wuzhy@linux.vnet.ibm.com, xemul@parallels.com, therbert@google.com, bhutchings@solarflare.com, xii@google.com, stephen@networkplumber.org To: Jason Wang Return-path: In-Reply-To: <53FAA607.3060307@redhat.com> Sender: linux-kernel-owner@vger.kernel.org List-Id: netdev.vger.kernel.org > On 08/24/2014 07:14 PM, Michael S. Tsirkin wrote: > > On Fri, Aug 22, 2014 at 07:52:22AM -0400, Pankaj Gupta wrote: > >>> On 08/20/2014 07:17 PM, Michael S. Tsirkin wrote: > >>>> On Wed, Aug 20, 2014 at 12:58:17PM +0200, Jiri Pirko wrote: > >>>>>> Mon, Aug 18, 2014 at 03:37:18PM CEST, pagupta@redhat.com wrote: > >>>>>>>> This patch publishes maximum number of tun/tap queues allocated as a > >>>>>>>> read_only module parameter which a user space application like > >>>>>>>> libvirt > >>>>>>>> can make use of to limit maximum number of queues. Value of > >>>>>>>> read_only > >>>>>>>> module parameter can be writable only at module load time. If no > >>>>>>>> value is set > >>>>>>>> at module load time a default value 256 is used which is equal to > >>>>>>>> maximum number > >>>>>>>> of vCPUS allowed by KVM. > >>>>>>>> > >>>>>>>> Administrator can specify maximum number of queues only at the > >>>>>>>> driver > >>>>>>>> module load time. > >>>>>>>> > >>>>>>>> Signed-off-by: Pankaj Gupta > >>>>>>>> --- > >>>>>>>> drivers/net/tun.c | 13 +++++++++++-- > >>>>>>>> 1 files changed, 11 insertions(+), 2 deletions(-) > >>>>>>>> > >>>>>>>> diff --git a/drivers/net/tun.c b/drivers/net/tun.c > >>>>>>>> index acaaf67..1f518e2 100644 > >>>>>>>> --- a/drivers/net/tun.c > >>>>>>>> +++ b/drivers/net/tun.c > >>>>>>>> @@ -119,6 +119,9 @@ struct tap_filter { > >>>>>>>> > >>>>>>>> #define TUN_FLOW_EXPIRE (3 * HZ) > >>>>>>>> > >>>>>>>> +static int max_tap_queues = MAX_TAP_QUEUES; > >>>>>>>> +module_param(max_tap_queues, int, S_IRUGO); > >>>>>> Please do not introduce new module paramaters. Please other ways to > >>>>>> interchange values with userspace. > >>>> I suggested this initially, but thinking more about it, I agree. > >>>> > >>>> It's a global limit (necessary to limit memory utilization by > >>>> userspace), but it should be possible to change it > >>>> after module load. > >>> How about pass this limit through ifr during TUNSETIFF, then > >>> alloc_netdev_mq() can use this limit. > >> Any other ideas/comments from the experts. Or shall I re-repost other > >> patches > >> in the series except this patch until we agree on one. > >> > > It's kind of useless without a way for userspace to discover > > how many queues it can create, no? > > > > We can implement ethtool_get_channels for tuntap. But I'm still not > clear why this is necessary. ethtool_get_channels for tuntap sounds good idea to retrieve number of queues configured. >