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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>
This commit is contained in:
Jason Wang 2013-01-23 03:59:12 +00:00 committed by David S. Miller
parent 844e88f044
commit edfb6a148c
1 changed files with 8 additions and 7 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

15
drivers/net/tun.c
View File

@ -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;