Hi Eric, I'm still trying to understand what you're saying before. Would this be better as following: 1) discard the tcp_internal_pacing() function. 2) remove where the tcp_internal_pacing() is called in the __tcp_transmit_skb() function.
If we do so, we could avoid 'too late to give up pacing'. Meanwhile, should we introduce the tcp_wstamp_ns socket field as commit (864e5c090749) does? Thanks, Jason On Wed, Jun 3, 2020 at 10:44 AM Eric Dumazet <eduma...@google.com> wrote: > > On Tue, Jun 2, 2020 at 7:42 PM Jason Xing <kerneljasonx...@gmail.com> wrote: > > > > I agree with you. The upstream has already dropped and optimized this > > part (commit 864e5c090749), so it would not happen like that. However > > the old kernels like LTS still have the problem which causes > > large-scale crashes on our thousands of machines after running for a > > long while. I will send the fix to the correct tree soon :) > > If you run BBR at scale (thousands of machines), you probably should > use sch_fq instead of internal pacing, > just saying ;) > > > > > > Thanks again, > > Jason > > > > On Wed, Jun 3, 2020 at 10:29 AM Eric Dumazet <eduma...@google.com> wrote: > > > > > > On Tue, Jun 2, 2020 at 6:53 PM Jason Xing <kerneljasonx...@gmail.com> > > > wrote: > > > > > > > > Hi Eric, > > > > > > > > I'm sorry that I didn't write enough clearly. We're running the > > > > pristine 4.19.125 linux kernel (the latest LTS version) and have been > > > > haunted by such an issue. This patch is high-important, I think. So > > > > I'm going to resend this email with the [patch 4.19] on the headline > > > > and cc Greg. > > > > > > Yes, please always give for which tree a patch is meant for. > > > > > > Problem is that your patch is not correct. > > > In these old kernels, tcp_internal_pacing() is called _after_ the > > > packet has been sent. > > > It is too late to 'give up pacing' > > > > > > The packet should not have been sent if the pacing timer is queued > > > (otherwise this means we do not respect pacing) > > > > > > So the bug should be caught earlier. check where tcp_pacing_check() > > > calls are missing. > > > > > > > > > > > > > > > > > > > > > Thanks, > > > > Jason > > > > > > > > On Tue, Jun 2, 2020 at 9:05 PM Eric Dumazet <eduma...@google.com> wrote: > > > > > > > > > > On Tue, Jun 2, 2020 at 1:05 AM <kerneljasonx...@gmail.com> wrote: > > > > > > > > > > > > From: Jason Xing <kerneljasonx...@gmail.com> > > > > > > > > > > > > TCP socks cannot be released because of the sock_hold() increasing > > > > > > the > > > > > > sk_refcnt in the manner of tcp_internal_pacing() when RTO happens. > > > > > > Therefore, this situation could increase the slab memory and then > > > > > > trigger > > > > > > the OOM if the machine has beening running for a long time. This > > > > > > issue, > > > > > > however, can happen on some machine only running a few days. > > > > > > > > > > > > We add one exception case to avoid unneeded use of sock_hold if the > > > > > > pacing_timer is enqueued. > > > > > > > > > > > > Reproduce procedure: > > > > > > 0) cat /proc/slabinfo | grep TCP > > > > > > 1) switch net.ipv4.tcp_congestion_control to bbr > > > > > > 2) using wrk tool something like that to send packages > > > > > > 3) using tc to increase the delay in the dev to simulate the busy > > > > > > case. > > > > > > 4) cat /proc/slabinfo | grep TCP > > > > > > 5) kill the wrk command and observe the number of objects and slabs > > > > > > in TCP. > > > > > > 6) at last, you could notice that the number would not decrease. > > > > > > > > > > > > Signed-off-by: Jason Xing <kerneljasonx...@gmail.com> > > > > > > Signed-off-by: liweishi <liwei...@kuaishou.com> > > > > > > Signed-off-by: Shujin Li <lishu...@kuaishou.com> > > > > > > --- > > > > > > net/ipv4/tcp_output.c | 3 ++- > > > > > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > > > > > > > > > diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c > > > > > > index cc4ba42..5cf63d9 100644 > > > > > > --- a/net/ipv4/tcp_output.c > > > > > > +++ b/net/ipv4/tcp_output.c > > > > > > @@ -969,7 +969,8 @@ static void tcp_internal_pacing(struct sock > > > > > > *sk, const struct sk_buff *skb) > > > > > > u64 len_ns; > > > > > > u32 rate; > > > > > > > > > > > > - if (!tcp_needs_internal_pacing(sk)) > > > > > > + if (!tcp_needs_internal_pacing(sk) || > > > > > > + hrtimer_is_queued(&tcp_sk(sk)->pacing_timer)) > > > > > > return; > > > > > > rate = sk->sk_pacing_rate; > > > > > > if (!rate || rate == ~0U) > > > > > > -- > > > > > > 1.8.3.1 > > > > > > > > > > > > > > > > Hi Jason. > > > > > > > > > > Please do not send patches that do not apply to current upstream > > > > > trees. > > > > > > > > > > Instead, backport to your kernels the needed fixes. > > > > > > > > > > I suspect that you are not using a pristine linux kernel, but some > > > > > heavily modified one and something went wrong in your backports. > > > > > Do not ask us to spend time finding what went wrong. > > > > > > > > > > Thank you.
