Messages in this thread | | | Date | Wed, 20 Aug 2014 13:53:44 +0200 | From | Jiri Pirko <> | Subject | Re: [RFC 2/4] tuntap: Publish tuntap maximum number of queues as module_param |
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Wed, Aug 20, 2014 at 01:49:07PM CEST, mst@redhat.com wrote: >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?
That is so far not possible. But I believe that it can be implemented. I'm just thinking out loud.
> >> > >> >-- >> >MST
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