diff options
Diffstat (limited to 'target/linux/generic/backport-4.19/396-5.8-sch_cake-don-t-try-to-reallocate-or-unshare-skb-unco.patch')
| -rw-r--r-- | target/linux/generic/backport-4.19/396-5.8-sch_cake-don-t-try-to-reallocate-or-unshare-skb-unco.patch | 96 |
1 files changed, 96 insertions, 0 deletions
diff --git a/target/linux/generic/backport-4.19/396-5.8-sch_cake-don-t-try-to-reallocate-or-unshare-skb-unco.patch b/target/linux/generic/backport-4.19/396-5.8-sch_cake-don-t-try-to-reallocate-or-unshare-skb-unco.patch new file mode 100644 index 0000000000..a36095c26c --- /dev/null +++ b/target/linux/generic/backport-4.19/396-5.8-sch_cake-don-t-try-to-reallocate-or-unshare-skb-unco.patch @@ -0,0 +1,96 @@ +From 9208d2863ac689a563b92f2161d8d1e7127d0add Mon Sep 17 00:00:00 2001 +From: Ilya Ponetayev <i.ponetaev@ndmsystems.com> +Date: Thu, 25 Jun 2020 22:12:07 +0200 +Subject: [PATCH] sch_cake: don't try to reallocate or unshare skb + unconditionally +MIME-Version: 1.0 +Content-Type: text/plain; charset=UTF-8 +Content-Transfer-Encoding: 8bit + +cake_handle_diffserv() tries to linearize mac and network header parts of +skb and to make it writable unconditionally. In some cases it leads to full +skb reallocation, which reduces throughput and increases CPU load. Some +measurements of IPv4 forward + NAPT on MIPS router with 580 MHz single-core +CPU was conducted. It appears that on kernel 4.9 skb_try_make_writable() +reallocates skb, if skb was allocated in ethernet driver via so-called +'build skb' method from page cache (it was discovered by strange increase +of kmalloc-2048 slab at first). + +Obtain DSCP value via read-only skb_header_pointer() call, and leave +linearization only for DSCP bleaching or ECN CE setting. And, as an +additional optimisation, skip diffserv parsing entirely if it is not needed +by the current configuration. + +Fixes: c87b4ecdbe8d ("sch_cake: Make sure we can write the IP header before changing DSCP bits") +Signed-off-by: Ilya Ponetayev <i.ponetaev@ndmsystems.com> +[ fix a few style issues, reflow commit message ] +Signed-off-by: Toke Høiland-Jørgensen <toke@redhat.com> +Signed-off-by: David S. Miller <davem@davemloft.net> +Signed-off-by: Kevin Darbyshire-Bryant <ldir@darbyshire-bryant.me.uk> +--- + net/sched/sch_cake.c | 41 ++++++++++++++++++++++++++++++----------- + 1 file changed, 30 insertions(+), 11 deletions(-) + +--- a/net/sched/sch_cake.c ++++ b/net/sched/sch_cake.c +@@ -1553,30 +1553,49 @@ static unsigned int cake_drop(struct Qdi + + static u8 cake_handle_diffserv(struct sk_buff *skb, u16 wash) + { +- int wlen = skb_network_offset(skb); ++ const int offset = skb_network_offset(skb); ++ u16 *buf, buf_; + u8 dscp; + + switch (tc_skb_protocol(skb)) { + case htons(ETH_P_IP): +- wlen += sizeof(struct iphdr); +- if (!pskb_may_pull(skb, wlen) || +- skb_try_make_writable(skb, wlen)) ++ buf = skb_header_pointer(skb, offset, sizeof(buf_), &buf_); ++ if (unlikely(!buf)) + return 0; + +- dscp = ipv4_get_dsfield(ip_hdr(skb)) >> 2; +- if (wash && dscp) ++ /* ToS is in the second byte of iphdr */ ++ dscp = ipv4_get_dsfield((struct iphdr *)buf) >> 2; ++ ++ if (wash && dscp) { ++ const int wlen = offset + sizeof(struct iphdr); ++ ++ if (!pskb_may_pull(skb, wlen) || ++ skb_try_make_writable(skb, wlen)) ++ return 0; ++ + ipv4_change_dsfield(ip_hdr(skb), INET_ECN_MASK, 0); ++ } ++ + return dscp; + + case htons(ETH_P_IPV6): +- wlen += sizeof(struct ipv6hdr); +- if (!pskb_may_pull(skb, wlen) || +- skb_try_make_writable(skb, wlen)) ++ buf = skb_header_pointer(skb, offset, sizeof(buf_), &buf_); ++ if (unlikely(!buf)) + return 0; + +- dscp = ipv6_get_dsfield(ipv6_hdr(skb)) >> 2; +- if (wash && dscp) ++ /* Traffic class is in the first and second bytes of ipv6hdr */ ++ dscp = ipv6_get_dsfield((struct ipv6hdr *)buf) >> 2; ++ ++ if (wash && dscp) { ++ const int wlen = offset + sizeof(struct ipv6hdr); ++ ++ if (!pskb_may_pull(skb, wlen) || ++ skb_try_make_writable(skb, wlen)) ++ return 0; ++ + ipv6_change_dsfield(ipv6_hdr(skb), INET_ECN_MASK, 0); ++ } ++ + return dscp; + + case htons(ETH_P_ARP): |