From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jason Wang Subject: Re: [RFC 2/4] tuntap: Publish tuntap maximum number of queues as module_param Date: Mon, 25 Aug 2014 10:57:11 +0800 Message-ID: <53FAA607.3060307@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> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Cc: 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: "Michael S. Tsirkin" , Pankaj Gupta Return-path: In-Reply-To: <20140824111421.GC9561@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.