This is a note to let you know that I've just added the patch titled
xen-netback: worse-case estimate in xenvif_rx_action is underestimating
to the 3.14-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary
The filename of the patch is:
xen-netback-worse-case-estimate-in-xenvif_rx_action-is-underestimating.patch
and it can be found in the queue-3.14 subdirectory.
If you, or anyone else, feels it should not be added to the stable tree,
please let <[email protected]> know about it.
>From foo@baz Thu Apr 10 20:31:46 PDT 2014
From: Paul Durrant <[email protected]>
Date: Fri, 28 Mar 2014 11:39:06 +0000
Subject: xen-netback: worse-case estimate in xenvif_rx_action is underestimating
From: Paul Durrant <[email protected]>
[ Upstream commit a02eb4732cf975d7fc71b6d1a71c058c9988b949 ]
The worse-case estimate for skb ring slot usage in xenvif_rx_action()
fails to take fragment page_offset into account. The page_offset does,
however, affect the number of times the fragmentation code calls
start_new_rx_buffer() (i.e. consume another slot) and the worse-case
should assume that will always return true. This patch adds the page_offset
into the DIV_ROUND_UP for each frag.
Unfortunately some frontends aggressively limit the number of requests
they post into the shared ring so to avoid an estimate that is 'too'
pessimal it is capped at MAX_SKB_FRAGS.
Signed-off-by: Paul Durrant <[email protected]>
Cc: Ian Campbell <[email protected]>
Cc: Wei Liu <[email protected]>
Cc: Sander Eikelenboom <[email protected]>
Signed-off-by: David S. Miller <[email protected]>
Signed-off-by: Greg Kroah-Hartman <[email protected]>
---
drivers/net/xen-netback/netback.c | 21 ++++++++++++++++++++-
1 file changed, 20 insertions(+), 1 deletion(-)
--- a/drivers/net/xen-netback/netback.c
+++ b/drivers/net/xen-netback/netback.c
@@ -493,9 +493,28 @@ static void xenvif_rx_action(struct xenv
PAGE_SIZE);
for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
unsigned int size;
+ unsigned int offset;
+
size = skb_frag_size(&skb_shinfo(skb)->frags[i]);
- max_slots_needed += DIV_ROUND_UP(size, PAGE_SIZE);
+ offset = skb_shinfo(skb)->frags[i].page_offset;
+
+ /* For a worse-case estimate we need to factor in
+ * the fragment page offset as this will affect the
+ * number of times xenvif_gop_frag_copy() will
+ * call start_new_rx_buffer().
+ */
+ max_slots_needed += DIV_ROUND_UP(offset + size,
+ PAGE_SIZE);
}
+
+ /* To avoid the estimate becoming too pessimal for some
+ * frontends that limit posted rx requests, cap the estimate
+ * at MAX_SKB_FRAGS.
+ */
+ if (max_slots_needed > MAX_SKB_FRAGS)
+ max_slots_needed = MAX_SKB_FRAGS;
+
+ /* We may need one more slot for GSO metadata */
if (skb_is_gso(skb) &&
(skb_shinfo(skb)->gso_type & SKB_GSO_TCPV4 ||
skb_shinfo(skb)->gso_type & SKB_GSO_TCPV6))
Patches currently in stable-queue which might be from [email protected]
are
queue-3.14/xen-netback-bug_on-in-xenvif_rx_action-not-catching-overflow.patch
queue-3.14/xen-netback-worse-case-estimate-in-xenvif_rx_action-is-underestimating.patch
queue-3.14/xen-netback-remove-pointless-clause-from-if-statement.patch
--
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