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authorRusty Russell <rusty@rustcorp.com.au>2008-08-15 15:15:10 -0700
committerDavid S. Miller <davem@davemloft.net>2008-08-15 19:52:31 -0700
commitf42157cb568c1eb02eca7df4da67553a9edae24a (patch)
treef8c104a73ae5558e104a07e254a9eafd7839269d
parentdb543c1f973cd1d557cc32ceee76737c1e4d2898 (diff)
tun: fallback if skb_alloc() fails on big packets
skb_alloc produces linear packets (using kmalloc()). That can fail, so should we fall back to making paged skbs. My original version of this patch always allocate paged skbs for big packets. But that made performance drop from 8.4 seconds to 8.8 seconds on 1G lguest->Host TCP xmit. So now we only do that as a fallback. Signed-off-by: Rusty Russell <rusty@rustcorp.com.au> Acked-by: Max Krasnyansky <maxk@qualcomm.com> Signed-off-by: David S. Miller <davem@davemloft.net>
-rw-r--r--drivers/net/tun.c66
1 files changed, 62 insertions, 4 deletions
diff --git a/drivers/net/tun.c b/drivers/net/tun.c
index 95931a5a988..6daea0c9186 100644
--- a/drivers/net/tun.c
+++ b/drivers/net/tun.c
@@ -358,6 +358,66 @@ static unsigned int tun_chr_poll(struct file *file, poll_table * wait)
return mask;
}
+/* prepad is the amount to reserve at front. len is length after that.
+ * linear is a hint as to how much to copy (usually headers). */
+static struct sk_buff *tun_alloc_skb(size_t prepad, size_t len, size_t linear,
+ gfp_t gfp)
+{
+ struct sk_buff *skb;
+ unsigned int i;
+
+ skb = alloc_skb(prepad + len, gfp|__GFP_NOWARN);
+ if (skb) {
+ skb_reserve(skb, prepad);
+ skb_put(skb, len);
+ return skb;
+ }
+
+ /* Under a page? Don't bother with paged skb. */
+ if (prepad + len < PAGE_SIZE)
+ return NULL;
+
+ /* Start with a normal skb, and add pages. */
+ skb = alloc_skb(prepad + linear, gfp);
+ if (!skb)
+ return NULL;
+
+ skb_reserve(skb, prepad);
+ skb_put(skb, linear);
+
+ len -= linear;
+
+ for (i = 0; i < MAX_SKB_FRAGS; i++) {
+ skb_frag_t *f = &skb_shinfo(skb)->frags[i];
+
+ f->page = alloc_page(gfp|__GFP_ZERO);
+ if (!f->page)
+ break;
+
+ f->page_offset = 0;
+ f->size = PAGE_SIZE;
+
+ skb->data_len += PAGE_SIZE;
+ skb->len += PAGE_SIZE;
+ skb->truesize += PAGE_SIZE;
+ skb_shinfo(skb)->nr_frags++;
+
+ if (len < PAGE_SIZE) {
+ len = 0;
+ break;
+ }
+ len -= PAGE_SIZE;
+ }
+
+ /* Too large, or alloc fail? */
+ if (unlikely(len)) {
+ kfree_skb(skb);
+ skb = NULL;
+ }
+
+ return skb;
+}
+
/* Get packet from user space buffer */
static __inline__ ssize_t tun_get_user(struct tun_struct *tun, struct iovec *iv, size_t count)
{
@@ -391,14 +451,12 @@ static __inline__ ssize_t tun_get_user(struct tun_struct *tun, struct iovec *iv,
return -EINVAL;
}
- if (!(skb = alloc_skb(len + align, GFP_KERNEL))) {
+ if (!(skb = tun_alloc_skb(align, len, gso.hdr_len, GFP_KERNEL))) {
tun->dev->stats.rx_dropped++;
return -ENOMEM;
}
- if (align)
- skb_reserve(skb, align);
- if (memcpy_fromiovec(skb_put(skb, len), iv, len)) {
+ if (skb_copy_datagram_from_iovec(skb, 0, iv, len)) {
tun->dev->stats.rx_dropped++;
kfree_skb(skb);
return -EFAULT;