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 4.9-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
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-4.9 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <stable@xxxxxxxxxxxxxxx> know about it.
>From foo@baz Thu Nov 9 09:48:01 CET 2017
From: Juergen Gross <jgross@xxxxxxxx>
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@xxxxxxxx>
[ 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@xxxxxxxx>
Reviewed-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Signed-off-by: Sasha Levin <alexander.levin@xxxxxxxxxxx>
Signed-off-by: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
---
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,
@@ -1626,11 +1627,12 @@ 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@xxxxxxxx are
queue-4.9/xen-netback-set-default-upper-limit-of-tx-rx-queues-to-8.patch