From d9a58a782e396a0f04e8445b7ba3763c8a48c7fe Mon Sep 17 00:00:00 2001 From: Ian Campbell <Ian.Campbell@citrix.com> Date: Mon, 7 Jan 2013 05:32:06 +0000 Subject: [PATCH] xen/netfront: improve truesize tracking Using RX_COPY_THRESHOLD is incorrect if the SKB is actually smaller than that. We have already accounted for this in NETFRONT_SKB_CB(skb)->pull_to so use that instead. Fixes WARN_ON from skb_try_coalesce. Signed-off-by: Ian Campbell <ian.campbell@citrix.com> Cc: Sander Eikelenboom <linux@eikelenboom.it> Cc: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: annie li <annie.li@oracle.com> Cc: xen-devel@lists.xen.org Cc: netdev@vger.kernel.org Cc: stable@kernel.org # 3.7.x only Acked-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net> --- drivers/net/xen-netfront.c | 27 ++++----------------------- 1 file changed, 4 insertions(+), 23 deletions(-) diff --git a/drivers/net/xen-netfront.c b/drivers/net/xen-netfront.c index c26e28b4bd9f9..7ffa43bd7cf9e 100644 --- a/drivers/net/xen-netfront.c +++ b/drivers/net/xen-netfront.c @@ -1015,29 +1015,10 @@ static int xennet_poll(struct napi_struct *napi, int budget) i = xennet_fill_frags(np, skb, &tmpq); /* - * Truesize approximates the size of true data plus - * any supervisor overheads. Adding hypervisor - * overheads has been shown to significantly reduce - * achievable bandwidth with the default receive - * buffer size. It is therefore not wise to account - * for it here. - * - * After alloc_skb(RX_COPY_THRESHOLD), truesize is set - * to RX_COPY_THRESHOLD + the supervisor - * overheads. Here, we add the size of the data pulled - * in xennet_fill_frags(). - * - * We also adjust for any unused space in the main - * data area by subtracting (RX_COPY_THRESHOLD - - * len). This is especially important with drivers - * which split incoming packets into header and data, - * using only 66 bytes of the main data area (see the - * e1000 driver for example.) On such systems, - * without this last adjustement, our achievable - * receive throughout using the standard receive - * buffer size was cut by 25%(!!!). - */ - skb->truesize += skb->data_len - RX_COPY_THRESHOLD; + * Truesize is the actual allocation size, even if the + * allocation is only partially used. + */ + skb->truesize += PAGE_SIZE * skb_shinfo(skb)->nr_frags; skb->len += skb->data_len; if (rx->flags & XEN_NETRXF_csum_blank) -- GitLab