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Date: Wed, 20 Aug 2014 13:46:20 +0200 From: Jiri Pirko <jiri@...nulli.us> To: "Michael S. Tsirkin" <mst@...hat.com> Cc: Pankaj Gupta <pagupta@...hat.com>, linux-kernel@...r.kernel.org, netdev@...r.kernel.org, davem@...emloft.net, jasowang@...hat.com, dgibson@...hat.com, vfalico@...il.com, edumazet@...gle.com, vyasevic@...hat.com, hkchu@...gle.com, wuzhy@...ux.vnet.ibm.com, xemul@...allels.com, therbert@...gle.com, bhutchings@...arflare.com, xii@...gle.com, stephen@...workplumber.org Subject: Re: [RFC 2/4] tuntap: Publish tuntap maximum number of queues as module_param Wed, Aug 20, 2014 at 01:17:24PM CEST, mst@...hat.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@...hat.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@...hat.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? > >-- >MST -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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