diff options
Diffstat (limited to 'target/linux/generic/backport-5.4/700-v5.5-net-core-allow-fast-GRO-for-skbs-with-Ethernet-heade.patch')
| -rw-r--r-- | target/linux/generic/backport-5.4/700-v5.5-net-core-allow-fast-GRO-for-skbs-with-Ethernet-heade.patch | 78 |
1 files changed, 0 insertions, 78 deletions
diff --git a/target/linux/generic/backport-5.4/700-v5.5-net-core-allow-fast-GRO-for-skbs-with-Ethernet-heade.patch b/target/linux/generic/backport-5.4/700-v5.5-net-core-allow-fast-GRO-for-skbs-with-Ethernet-heade.patch deleted file mode 100644 index 24b76cdca4..0000000000 --- a/target/linux/generic/backport-5.4/700-v5.5-net-core-allow-fast-GRO-for-skbs-with-Ethernet-heade.patch +++ /dev/null @@ -1,78 +0,0 @@ -From: Alexander Lobakin <alobakin@dlink.ru> -Date: Fri, 15 Nov 2019 12:11:35 +0300 -Subject: [PATCH] net: core: allow fast GRO for skbs with Ethernet header in - head - -Commit 78d3fd0b7de8 ("gro: Only use skb_gro_header for completely -non-linear packets") back in May'09 (v2.6.31-rc1) has changed the -original condition '!skb_headlen(skb)' to -'skb->mac_header == skb->tail' in gro_reset_offset() saying: "Since -the drivers that need this optimisation all provide completely -non-linear packets" (note that this condition has become the current -'skb_mac_header(skb) == skb_tail_pointer(skb)' later with commmit -ced14f6804a9 ("net: Correct comparisons and calculations using -skb->tail and skb-transport_header") without any functional changes). - -For now, we have the following rough statistics for v5.4-rc7: -1) napi_gro_frags: 14 -2) napi_gro_receive with skb->head containing (most of) payload: 83 -3) napi_gro_receive with skb->head containing all the headers: 20 -4) napi_gro_receive with skb->head containing only Ethernet header: 2 - -With the current condition, fast GRO with the usage of -NAPI_GRO_CB(skb)->frag0 is available only in the [1] case. -Packets pushed by [2] and [3] go through the 'slow' path, but -it's not a problem for them as they already contain all the needed -headers in skb->head, so pskb_may_pull() only moves skb->data. - -The layout of skbs in the fourth [4] case at the moment of -dev_gro_receive() is identical to skbs that have come through [1], -as napi_frags_skb() pulls Ethernet header to skb->head. The only -difference is that the mentioned condition is always false for them, -because skb_put() and friends irreversibly alter the tail pointer. -They also go through the 'slow' path, but now every single -pskb_may_pull() in every single .gro_receive() will call the *really* -slow __pskb_pull_tail() to pull headers to head. This significantly -decreases the overall performance for no visible reasons. - -The only two users of method [4] is: -* drivers/staging/qlge -* drivers/net/wireless/iwlwifi (all three variants: dvm, mvm, mvm-mq) - -Note that in case with wireless drivers we can't use [1] -(napi_gro_frags()) at least for now and mac80211 stack always -performs pushes and pulls anyways, so performance hit is inavoidable. - -At the moment of v2.6.31 the mentioned change was necessary (that's -why I don't add the "Fixes:" tag), but it became obsolete since -skb_gro_mac_header() has gone in commit a50e233c50db ("net-gro: -restore frag0 optimization"), so we can simply revert the condition -in gro_reset_offset() to allow skbs from [4] go through the 'fast' -path just like in case [1]. - -This was tested on a 600 MHz MIPS CPU and a custom driver and this -patch gave boosts up to 40 Mbps to method [4] in both directions -comparing to net-next, which made overall performance relatively -close to [1] (without it, [4] is the slowest). - -v2: -- Add more references and explanations to commit message -- Fix some typos ibid -- No functional changes - -Signed-off-by: Alexander Lobakin <alobakin@dlink.ru> -Signed-off-by: David S. Miller <davem@davemloft.net> ---- - ---- a/net/core/dev.c -+++ b/net/core/dev.c -@@ -5475,8 +5475,7 @@ static inline void skb_gro_reset_offset( - NAPI_GRO_CB(skb)->frag0 = NULL; - NAPI_GRO_CB(skb)->frag0_len = 0; - -- if (skb_mac_header(skb) == skb_tail_pointer(skb) && -- pinfo->nr_frags && -+ if (!skb_headlen(skb) && pinfo->nr_frags && - !PageHighMem(skb_frag_page(frag0)) && - (!NET_IP_ALIGN || !((skb_frag_off(frag0) + nhoff) & 3))) { - NAPI_GRO_CB(skb)->frag0 = skb_frag_address(frag0); |