[PATCH net-next 4/4] tuntap: Increase the number of queues in tun.

From: Pankaj Gupta
Date: Tue Nov 18 2014 - 13:08:11 EST

Networking under kvm works best if we allocate a per-vCPU RX and TX
queue in a virtual NIC. This requires a per-vCPU queue on the host side.

It is now safe to increase the maximum number of queues.
Preceding patches:
net: allow large number of rx queues
tuntap: Reduce the size of tun_struct by using flex array
tuntap: Accepts tuntap max queue length as net sysctl parameter

made sure this won't cause failures due to high order memory
allocations. Increase it to 256: this is the max number of vCPUs
KVM supports.

Signed-off-by: Pankaj Gupta <pagupta@xxxxxxxxxx>
Reviewed-by: David Gibson <dgibson@xxxxxxxxxx>
drivers/net/tun.c | 9 +++++----
1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index a9b3eb4..2fb31b7 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -115,10 +115,11 @@ struct tap_filter {
unsigned char addr[FLT_EXACT_COUNT][ETH_ALEN];

-/* DEFAULT_MAX_NUM_RSS_QUEUES were chosen to let the rx/tx queues allocated for
- * the netdevice to be fit in one page. So we can make sure the success of
- * memory allocation. TODO: increase the limit. */
+/* MAX_TAP_QUEUES 256 is chosen to allow rx/tx queues to be equal
+ * to max number of vCPUS in guest. Also, we are making sure here
+ * queue memory allocation do not fail.
+ */
+#define MAX_TAP_QUEUES 256
#define MIN_TAP_QUEUES 1
#define MAX_TAP_FLOWS 4096


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