Re: 3.7.8/amd64 full interrupt hangs due to iwlwifi under big nfs copies out

Eric Dumazet
2013-02-20T15:11:07Z

On Wed, 2013-02-20 at 10:15 +0100, Johannes Berg wrote:

> OTOH, this affects the protocol, and when you really can't allocate any
> order-1 pages you pointed out yourself that many other things also won't
> work, so I'm not really sure it makes a big difference if we change the
> driver?

It will make a huge difference, even on non pressure mode, as TCP
receive window will grow twice faster.

Unless wifi speed reaches 10Gbps, following patch should do the trick

diff --git a/drivers/net/wireless/iwlwifi/dvm/rx.c b/drivers/net/wireless/iwlwifi/dvm/rx.c
index a4eed20..77a3ee3 100644
--- a/drivers/net/wireless/iwlwifi/dvm/rx.c
+++ b/drivers/net/wireless/iwlwifi/dvm/rx.c
@@ -750,7 +750,12 @@ static void iwlagn_pass_packet_to_mac80211(struct iwl_priv *priv,
/* Dont use dev_alloc_skb(), we'll have enough headroom once
* ieee80211_hdr pulled.
*/
- skb = alloc_skb(128, GFP_ATOMIC);
+ fraglen = 128;
+ /* if we use order-1 pages, copy to get better TCP performance */
+ if (rxb->truesize > PAGE_SIZE)
+ fraglen = max_t(unsigned, fraglen, len);
+
+ skb = alloc_skb(fraglen, GFP_ATOMIC);
if (!skb) {
IWL_ERR(priv, "alloc_skb failed\n");
return;