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Date: Thu, 01 Oct 2015 13:16:17 +0200
From: Mike Galbraith <umgwanakikbuti@...il.com>
To: Herbert Xu <herbert@...dor.apana.org.au>
Cc: netdev@...r.kernel.org, pshelar@...ira.com,
linux-kernel@...r.kernel.org
Subject: Re: [regression] 6ae459bd skbuff: Fix skb checksum flag on skb pull
On Thu, 2015-10-01 at 16:42 +0800, Herbert Xu wrote:
> Mike Galbraith <umgwanakikbuti@...il.com> wrote:
> >
> > homer:/usr/local/src/kernel/linux-3.x.git # time strace -vvvfFtT git remote update 2> /strace.out
> > Fetching origin
> >
> > real 2m9.164s
> > user 0m1.616s
> > sys 0m0.316s
> >
> > 2 minutes of thumb twiddling should have been..
> >
> > homer:/usr/local/src/kernel/linux-3.x.git # time git remote update
> > Fetching origin
> >
> > real 0m0.213s
> > user 0m0.156s
> > sys 0m0.036s
> >
> > Daemon runs as user git like so, with all repositories living in ~git:
> > /usr/lib/git/git-daemon --syslog --detach --reuseaddr --user=git --group=daemon --pid-file=/var/run/git-daemon.pid --export-all --user-path
> >
> > Bisected and post bisect verified by applying/removing a revert.
>
> So do you use VXLANs?
Nope. It really really is that patch though.
> If this patch is indeed causing the regression you should be able
> to spot some differences in the tcpdump. Can you confirm this?
Will this work instead?
---
include/linux/skbuff.h | 4 +++-
1 file changed, 3 insertions(+), 1 deletion(-)
--- a/include/linux/skbuff.h
+++ b/include/linux/skbuff.h
@@ -2708,8 +2708,10 @@ static inline void skb_postpull_rcsum(st
if (skb->ip_summed == CHECKSUM_COMPLETE)
skb->csum = csum_sub(skb->csum, csum_partial(start, len, 0));
else if (skb->ip_summed == CHECKSUM_PARTIAL &&
- skb_checksum_start_offset(skb) <= len)
+ skb_checksum_start_offset(skb) <= len) {
skb->ip_summed = CHECKSUM_NONE;
+ trace_printk("skb_checksum_start_offset(skb) = %d len = %u\n", skb_checksum_start_offset(skb), len);
+ }
}
unsigned char *skb_pull_rcsum(struct sk_buff *skb, unsigned int len);
# tracer: nop
#
# nop latency trace v1.1.5 on 4.3.0-master
# --------------------------------------------------------------------
# latency: 0 us, #10/10, CPU#0 | (M:desktop VP:0, KP:0, SP:0 HP:0 #P:8)
# -----------------
# | task: -0 (uid:0 nice:0 policy:0 rt_prio:0)
# -----------------
#
# _------=> CPU#
# / _-----=> irqs-off
# | / _----=> need-resched
# || / _---=> hardirq/softirq
# ||| / _--=> preempt-depth
# |||| / delay
# cmd pid ||||| time | caller
# \ / ||||| \ | /
git-10826 2..s1 10668371us+: ip6_input_finish+0x1e8/0x3e0: skb_checksum_start_offset(skb) = 0 len = 40
git-10826 2..s1 10668386us@: <stack trace>
=> ip6_rcv_finish+0x34/0xa0
=> ipv6_rcv+0x2b7/0x4c0
=> __netif_receive_skb_core+0x634/0x990
=> __netif_receive_skb+0x18/0x60
=> process_backlog+0x8d/0x120
=> net_rx_action+0x13a/0x300
=> __do_softirq+0xcc/0x240
=> do_softirq_own_stack+0x1c/0x30
=> do_softirq+0x31/0x40
=> __local_bh_enable_ip+0x78/0x80
=> ip6_finish_output2+0x171/0x460
=> ip6_finish_output+0x89/0xe0
=> ip6_output+0x44/0xd0
=> ip6_xmit+0x208/0x500
=> inet6_csk_xmit+0x65/0xa0
=> tcp_transmit_skb+0x494/0x860
=> tcp_connect+0x63e/0x7f0
=> tcp_v6_connect+0x2f3/0x570
=> __inet_stream_connect+0x93/0x2e0
=> inet_stream_connect+0x38/0x50
=> SYSC_connect+0x69/0xd0
=> SyS_connect+0xe/0x10
=> entry_SYSCALL_64_fastpath+0x16/0x6e
<idle>-0 2..s. 11666764us : ip6_input_finish+0x1e8/0x3e0: skb_checksum_start_offset(skb) = 0 len = 40
<idle>-0 2..s. 11666768us$: <stack trace>
=> ip6_rcv_finish+0x34/0xa0
=> ipv6_rcv+0x2b7/0x4c0
=> __netif_receive_skb_core+0x634/0x990
=> __netif_receive_skb+0x18/0x60
=> process_backlog+0x8d/0x120
=> net_rx_action+0x13a/0x300
=> __do_softirq+0xcc/0x240
=> irq_exit+0x8c/0xa0
=> smp_apic_timer_interrupt+0x45/0x60
=> apic_timer_interrupt+0x7f/0x90
=> start_secondary+0x103/0x130
<idle>-0 2..s. 13670053us : ip6_input_finish+0x1e8/0x3e0: skb_checksum_start_offset(skb) = 0 len = 40
<idle>-0 2..s. 13670058us$: <stack trace>
=> ip6_rcv_finish+0x34/0xa0
=> ipv6_rcv+0x2b7/0x4c0
=> __netif_receive_skb_core+0x634/0x990
=> __netif_receive_skb+0x18/0x60
=> process_backlog+0x8d/0x120
=> net_rx_action+0x13a/0x300
=> __do_softirq+0xcc/0x240
=> irq_exit+0x8c/0xa0
=> smp_apic_timer_interrupt+0x45/0x60
=> apic_timer_interrupt+0x7f/0x90
=> cpuidle_enter+0x17/0x20
=> call_cpuidle+0x32/0x60
=> cpu_startup_entry+0x217/0x2d0
=> start_secondary+0x103/0x130
<idle>-0 2..s. 17676620us : ip6_input_finish+0x1e8/0x3e0: skb_checksum_start_offset(skb) = 0 len = 40
<idle>-0 2..s. 17676625us$: <stack trace>
=> ip6_rcv_finish+0x34/0xa0
=> ipv6_rcv+0x2b7/0x4c0
=> __netif_receive_skb_core+0x634/0x990
=> __netif_receive_skb+0x18/0x60
=> process_backlog+0x8d/0x120
=> net_rx_action+0x13a/0x300
=> __do_softirq+0xcc/0x240
=> irq_exit+0x8c/0xa0
=> smp_apic_timer_interrupt+0x45/0x60
=> apic_timer_interrupt+0x7f/0x90
=> cpuidle_enter+0x17/0x20
=> call_cpuidle+0x32/0x60
=> cpu_startup_entry+0x217/0x2d0
=> start_secondary+0x103/0x130
<idle>-0 2..s. 25697779us : ip6_input_finish+0x1e8/0x3e0: skb_checksum_start_offset(skb) = 0 len = 40
<idle>-0 2..s. 25697783us : <stack trace>
=> ip6_rcv_finish+0x34/0xa0
=> ipv6_rcv+0x2b7/0x4c0
=> __netif_receive_skb_core+0x634/0x990
=> __netif_receive_skb+0x18/0x60
=> process_backlog+0x8d/0x120
=> net_rx_action+0x13a/0x300
=> __do_softirq+0xcc/0x240
=> irq_exit+0x8c/0xa0
=> smp_apic_timer_interrupt+0x45/0x60
=> apic_timer_interrupt+0x7f/0x90
=> cpuidle_enter+0x17/0x20
=> call_cpuidle+0x32/0x60
=> cpu_startup_entry+0x217/0x2d0
=> start_secondary+0x103/0x130
--
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