Re: [PATCH v4 net-next 2/2 tuntap: Increase the number of queues in tun.
From: "Michael S. Tsirkin" <mst@redhat.com>
Date: 2015-01-06 09:49:42
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On Tue, Jan 06, 2015 at 11:09:16AM +0530, Pankaj Gupta wrote:
quoted hunk ↗ jump to hunk
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 patch: 'net: allow large number of rx queues' 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. Size of tun_struct changes from 8512 to 10496 after this patch. This keeps pages allocated for tun_struct before and after the patch to 3. Signed-off-by: Pankaj Gupta <redacted> Reviewed-by: David Gibson <redacted> --- 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.
VCPUs I think.
Also, we are making sure here + * queue memory allocation do not fail.
What does this mean? How are we making sure? I would drop this phrase really.
+ */ +#define MAX_TAP_QUEUES 256 #define MAX_TAP_FLOWS 4096 #define TUN_FLOW_EXPIRE (3 * HZ) -- 1.8.3.1