2014-11-24 20:24:43

by Pankaj Gupta

Subject: [PATCH v2 net-next 3/3] tuntap: Increase the number of queues in tun.

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

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 <[email protected]>
Reviewed-by: David Gibson <[email protected]>
---
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 e3fa65a..a19dc5f8 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -113,10 +113,11 @@ 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. */
-#define MAX_TAP_QUEUES DEFAULT_MAX_NUM_RSS_QUEUES
+/* 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 MAX_TAP_FLOWS 4096

#define TUN_FLOW_EXPIRE (3 * HZ)
--
1.8.3.1

2014-11-24 18:47:07

by Pankaj Gupta

Subject: Re: [PATCH v2 net-next 3/3] tuntap: Increase the number of queues in tun.

Adding Michael to CC.

>
> 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
>
> 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 <[email protected]>
> Reviewed-by: David Gibson <[email protected]>
> ---
> 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 e3fa65a..a19dc5f8 100644
> --- a/drivers/net/tun.c
> +++ b/drivers/net/tun.c
> @@ -113,10 +113,11 @@ 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. */
> -#define MAX_TAP_QUEUES DEFAULT_MAX_NUM_RSS_QUEUES
> +/* 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 MAX_TAP_FLOWS 4096
>
> #define TUN_FLOW_EXPIRE (3 * HZ)
> --
> 1.8.3.1
>
>