Re: [PATCH v2 4.19] tcp: fix TCP socks unreleased in BBR mode

[Jason Xing]

On Tue, Aug 11, 2020 at 11:33 PM Eric Dumazet <eric.dumazet@xxxxxxxxx> wrote:
>
>
>
> On 8/11/20 3:37 AM, Jason Xing wrote:
> > Hi everyone,
> >
> > Could anyone take a look at this issue? I believe it is of high-importance.
> > Though Eric gave the proper patch a few months ago, the stable branch
> > still hasn't applied or merged this fix. It seems this patch was
> > forgotten :(
>
>
> Sure, I'll take care of this shortly.

Hi Eric,

It has been a very long time. It seems this issue was left behind and
almost forgotten, I think.
Could you mind taking some time to fix this up if you still consider
it as important?
Our team has been waiting for your patchset. Afterall, it once had a
huge impact on our
thousands and hundreds of machines.

thanks,
Jason

>
> Thanks.
>
> >
> > Thanks,
> > Jason
> >
> > On Thu, Jun 4, 2020 at 9:47 PM Jason Xing <kerneljasonxing@xxxxxxxxx> wrote:
> >>
> >> On Thu, Jun 4, 2020 at 9:10 PM Eric Dumazet <edumazet@xxxxxxxxxx> wrote:
> >>>
> >>> On Thu, Jun 4, 2020 at 2:01 AM <kerneljasonxing@xxxxxxxxx> wrote:
> >>>>
> >>>> From: Jason Xing <kerneljasonxing@xxxxxxxxx>
> >>>>
> >>>> When using BBR mode, too many tcp socks cannot be released because of
> >>>> duplicate use of the sock_hold() in the manner of tcp_internal_pacing()
> >>>> when RTO happens. Therefore, this situation maddly increases the slab
> >>>> memory and then constantly triggers the OOM until crash.
> >>>>
> >>>> Besides, in addition to BBR mode, if some mode applies pacing function,
> >>>> it could trigger what we've discussed above,
> >>>>
> >>>> 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 and loss to simulate the RTO 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.
> >>>>
> >>>> v2: extend the timer which could cover all those related potential risks
> >>>> (suggested by Eric Dumazet and Neal Cardwell)
> >>>>
> >>>> Signed-off-by: Jason Xing <kerneljasonxing@xxxxxxxxx>
> >>>> Signed-off-by: liweishi <liweishi@xxxxxxxxxxxx>
> >>>> Signed-off-by: Shujin Li <lishujin@xxxxxxxxxxxx>
> >>>
> >>> That is not how things work really.
> >>>
> >>> I will submit this properly so that stable teams do not have to guess
> >>> how to backport this to various kernels.
> >>>
> >>> Changelog is misleading, this has nothing to do with BBR, we need to be precise.
> >>>
> >>
> >> Thanks for your help. I can finally apply this patch into my kernel.
> >>
> >> Looking forward to your patchset :)
> >>
> >> Jason
> >>
> >>> Thank you.