tuntap: reduce memory using of queues (edfb6a14) · Commits · 戴 / test

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:

Dirk 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:

Jason Wang <jasowang@redhat.com> Acked-by:

Michael S. Tsirkin <mst@redhat.com> Signed-off-by:

David S. Miller <davem@davemloft.net>

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;

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