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: 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>
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@ -109,11 +109,10 @@ struct tap_filter {
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unsigned char addr[FLT_EXACT_COUNT][ETH_ALEN];
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};
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/* 1024 is probably a high enough limit: modern hypervisors seem to support on
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* the order of 100-200 CPUs so this leaves us some breathing space if we want
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* to match a queue per guest CPU.
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*/
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#define MAX_TAP_QUEUES 1024
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/* DEFAULT_MAX_NUM_RSS_QUEUES were choosed to let the rx/tx queues allocated for
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* the netdevice to be fit in one page. So we can make sure the success of
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* memory allocation. TODO: increase the limit. */
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#define MAX_TAP_QUEUES DEFAULT_MAX_NUM_RSS_QUEUES
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#define TUN_FLOW_EXPIRE (3 * HZ)
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@ -1583,6 +1582,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
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else {
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char *name;
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unsigned long flags = 0;
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int queues = ifr->ifr_flags & IFF_MULTI_QUEUE ?
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MAX_TAP_QUEUES : 1;
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if (!ns_capable(net->user_ns, CAP_NET_ADMIN))
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return -EPERM;
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@ -1606,8 +1607,8 @@ static int tun_set_iff(struct net *net, struct file *file, struct ifreq *ifr)
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name = ifr->ifr_name;
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dev = alloc_netdev_mqs(sizeof(struct tun_struct), name,
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tun_setup,
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MAX_TAP_QUEUES, MAX_TAP_QUEUES);
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tun_setup, queues, queues);
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if (!dev)
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return -ENOMEM;
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