Messages in this thread | | | Date | Wed, 20 Aug 2014 13:49:07 +0200 | From | "Michael S. Tsirkin" <> | Subject | Re: [RFC 2/4] tuntap: Publish tuntap maximum number of queues as module_param |
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On Wed, Aug 20, 2014 at 01:46:20PM +0200, Jiri Pirko wrote: > Wed, Aug 20, 2014 at 01:17:24PM CEST, mst@redhat.com 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 <pagupta@redhat.com> > >> >--- > >> > 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. > > > >Additionally, userspace that has the FD should be able to > >retrieve the value without guessing that the FD is > >for the tun device (and not e.g. macvtap). > >To retrieve the value, an ioctl is probably the > >cleanest approach. > > > >To set it, how about a sysctl? I think the limit can also apply to > >all devices, not just tun. > > Or netlink?
Are there examples of netlink being used to set global defaults as opposed to per-device parameters?
> > > >-- > >MST
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