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Date: Wed, 9 Sep 2020 23:21:50 -0400 From: Neal Cardwell <ncardwell@...gle.com> To: Martin KaFai Lau <kafai@...com> Cc: David Miller <davem@...emloft.net>, Netdev <netdev@...r.kernel.org> Subject: Re: [PATCH net-next 0/4] tcp: increase flexibility of EBPF congestion control initialization On Wed, Sep 9, 2020 at 8:36 PM Martin KaFai Lau <kafai@...com> wrote: > > On Wed, Sep 09, 2020 at 02:15:52PM -0400, Neal Cardwell wrote: > > This patch series reorganizes TCP congestion control initialization so that if > > EBPF code called by tcp_init_transfer() sets the congestion control algorithm > > by calling setsockopt(TCP_CONGESTION) then the TCP stack initializes the > > congestion control module immediately, instead of having tcp_init_transfer() > > later initialize the congestion control module. > > > > This increases flexibility for the EBPF code that runs at connection > > establishment time, and simplifies the code. > > > > This has the following benefits: > > > > (1) This allows CC module customizations made by the EBPF called in > > tcp_init_transfer() to persist, and not be wiped out by a later > > call to tcp_init_congestion_control() in tcp_init_transfer(). > > > > (2) Does not flip the order of EBPF and CC init, to avoid causing bugs > > for existing code upstream that depends on the current order. > > > > (3) Does not cause 2 initializations for for CC in the case where the > > EBPF called in tcp_init_transfer() wants to set the CC to a new CC > > algorithm. > > > > (4) Allows follow-on simplifications to the code in net/core/filter.c > > and net/ipv4/tcp_cong.c, which currently both have some complexity > > to special-case CC initialization to avoid double CC > > initialization if EBPF sets the CC. > Thanks for this work. Only have one nit in patch 3 for consideration. > > Acked-by: Martin KaFai Lau <kafai@...com> Thanks for the review! I like your suggestion in patch 3 to further simplify the code. Do you mind submitting your idea for a follow-on clean-up/refactor as a separate follow-on commit? thanks, neal
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