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Message-ID: <CAL+tcoCW7o-RcQ40NdZKwfcoqn5V9K4kjKpYpiT0E38k7yyc2Q@mail.gmail.com> Date: Tue, 30 May 2023 22:31:38 +0800 From: Jason Xing <kerneljasonxing@...il.com> To: Eric Dumazet <edumazet@...gle.com> Cc: fuyuanli <fuyuanli@...iglobal.com>, "David S. Miller" <davem@...emloft.net>, Jakub Kicinski <kuba@...nel.org>, Paolo Abeni <pabeni@...hat.com>, Neal Cardwell <ncardwell@...gle.com>, ycheng <ycheng@...gle.com>, toke <toke@...e.dk>, netdev@...r.kernel.org, Weiping Zhang <zhangweiping@...iglobal.com>, Tio Zhang <tiozhang@...iglobal.com> Subject: Re: [PATCH net v2] tcp: fix mishandling when the sack compression is deferred On Tue, May 30, 2023 at 10:23 PM Eric Dumazet <edumazet@...gle.com> wrote: > > On Tue, May 30, 2023 at 4:19 PM fuyuanli <fuyuanli@...iglobal.com> wrote: > > > > In this patch, we mainly do two things which could be separately > > found as the following links: > > 1) fix not sending a compressed ack if it's deferred. > > 2) use the ICSK_ACK_TIMER flag in tcp_sack_compress_send_ack() and > > tcp_event_ack_sent() in order we can cancel it if it's deferred. > > > > Here are more details in the old logic: > > When sack compression is triggered in the tcp_compressed_ack_kick(), > > if the sock is owned by user, it will set TCP_DELACK_TIMER_DEFERRED > > and then defer to the release cb phrase. Later once user releases > > the sock, tcp_delack_timer_handler() should send a ack as expected, > > which, however, cannot happen due to lack of ICSK_ACK_TIMER flag. > > Therefore, the receiver would not sent an ack until the sender's > > retransmission timeout. It definitely increases unnecessary latency. > > > > Fixes: 5d9f4262b7ea ("tcp: add SACK compression") > > Suggested-by: Eric Dumazet <edumazet@...gle.com> > > Signed-off-by: fuyuanli <fuyuanli@...iglobal.com> > > Signed-off-by: Jason Xing <kerneljasonxing@...il.com> > > Link: https://lore.kernel.org/netdev/20230529113804.GA20300@didi-ThinkCentre-M920t-N000/ > > Link: https://lore.kernel.org/netdev/20230530023737.584-1-kerneljasonxing@gmail.com/ > > --- > > v2: > > 1) change the commit title and message > > 2) reuse the delayed ack logic when handling the sack compression > > as suggested by Eric. > > 3) "merge" another related patch into this one. See the second link. > > No. > > This is not the patch I suggested. I'm confused. You said in the previous email: "As a bonus, no need to send one patch for net, and another in net-next, trying to 'fix' issues that should have been fixed cleanly in a single patch." So we added "introducing ICSK_ACK_TIMER flag for sack compression" to fix them on top of the patch you suggested. I can remove the Suggested-by label. For now, I do care about your opinion on the current patch. Well...should I give up introducing that flag and then leave that 'issue' behind? :S Thanks, Jason
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