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Commit edfb6a14 authored by Jason Wang's avatar Jason Wang Committed by David S. Miller
Browse files

tuntap: reduce memory using of queues 



A MAX_TAP_QUEUES(1024) queues of tuntap device is always allocated
unconditionally even userspace only requires a single queue device. This is
unnecessary and will lead a very high order of page allocation when has a high
possibility to fail. Solving this by creating a one queue net device when
userspace only use one queue and also reduce MAX_TAP_QUEUES to
DEFAULT_MAX_NUM_RSS_QUEUES which can guarantee the success of
the allocation.

Reported-by: default avatarDirk Hohndel <dirk@hohndel.org>
Cc: Eric Dumazet <eric.dumazet@gmail.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Michael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarJason Wang <jasowang@redhat.com>
Acked-by: default avatarMichael S. Tsirkin <mst@redhat.com>
Signed-off-by: default avatarDavid S. Miller <davem@davemloft.net>
parent 844e88f0

drivers/net/tun.c

+8 −7
Original line number Diff line number Diff line
@@ -109,11 +109,10 @@ struct tap_filter { 
	unsigned char	addr[FLT_EXACT_COUNT][ETH_ALEN];

};



/* 1024 is probably a high enough limit: modern hypervisors seem to support on

 * the order of 100-200 CPUs so this leaves us some breathing space if we want

 * to match a queue per guest CPU.

 */

#define MAX_TAP_QUEUES 1024

/* DEFAULT_MAX_NUM_RSS_QUEUES were choosed 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



#define TUN_FLOW_EXPIRE (3 * HZ)
@@ -1583,6 +1582,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) 
	else {

		char *name;

		unsigned long flags = 0;

		int queues = ifr->ifr_flags & IFF_MULTI_QUEUE ?

			     MAX_TAP_QUEUES : 1;



		if (!ns_capable(net->user_ns, CAP_NET_ADMIN))

			return -EPERM;
@@ -1606,8 +1607,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr) 
			name = ifr->ifr_name;



		dev = alloc_netdev_mqs(sizeof(struct tun_struct), name,

				       tun_setup,

				       MAX_TAP_QUEUES, MAX_TAP_QUEUES);

				       tun_setup, queues, queues);



		if (!dev)

			return -ENOMEM;