This is a note to let you know that I've just added the patch titled

xen/netback: set default upper limit of tx/rx queues to 8

to the 3.18-stable tree which can be found at: http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git%3Ba=su...

The filename of the patch is: xen-netback-set-default-upper-limit-of-tx-rx-queues-to-8.patch and it can be found in the queue-3.18 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let stable@vger.kernel.org know about it.

From foo@baz Thu Nov 9 10:19:57 CET 2017

From: Juergen Gross jgross@suse.com Date: Tue, 10 Jan 2017 14:32:52 +0100 Subject: xen/netback: set default upper limit of tx/rx queues to 8

From: Juergen Gross jgross@suse.com

[ Upstream commit 56dd5af9bc23d0d5d23bb207c477715b4c2216c5 ]

The default for the maximum number of tx/rx queues of one interface is the number of cpus of the system today. As each queue pair reserves 512 grant pages this default consumes a ridiculous number of grants for large guests.

Limit the queue number to 8 as default. This value can be modified via a module parameter if required.

Signed-off-by: Juergen Gross jgross@suse.com Reviewed-by: Boris Ostrovsky boris.ostrovsky@oracle.com Signed-off-by: Boris Ostrovsky boris.ostrovsky@oracle.com Signed-off-by: Sasha Levin alexander.levin@verizon.com Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- drivers/net/xen-netback/netback.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)

--- a/drivers/net/xen-netback/netback.c +++ b/drivers/net/xen-netback/netback.c @@ -67,6 +67,7 @@ module_param(rx_drain_timeout_msecs, uin unsigned int rx_stall_timeout_msecs = 60000; module_param(rx_stall_timeout_msecs, uint, 0444);

+#define MAX_QUEUES_DEFAULT 8 unsigned int xenvif_max_queues; module_param_named(max_queues, xenvif_max_queues, uint, 0644); MODULE_PARM_DESC(max_queues, @@ -2189,11 +2190,12 @@ static int __init netback_init(void) if (!xen_domain()) return -ENODEV;

- /* Allow as many queues as there are CPUs if user has not + /* Allow as many queues as there are CPUs but max. 8 if user has not * specified a value. */ if (xenvif_max_queues == 0) - xenvif_max_queues = num_online_cpus(); + xenvif_max_queues = min_t(unsigned int, MAX_QUEUES_DEFAULT, + num_online_cpus());

if (fatal_skb_slots < XEN_NETBK_LEGACY_SLOTS_MAX) { pr_info("fatal_skb_slots too small (%d), bump it to XEN_NETBK_LEGACY_SLOTS_MAX (%d)\n",

Patches currently in stable-queue which might be from jgross@suse.com are

queue-3.18/xen-netback-set-default-upper-limit-of-tx-rx-queues-to-8.patch