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Message-ID: <CANn89i+HK5vny8qo89_+4PqZj9rBcGi6sVfSgN4HSpqqoUr6fw@mail.gmail.com> Date: Tue, 30 May 2023 16:22:58 +0200 From: Eric Dumazet <edumazet@...gle.com> To: fuyuanli <fuyuanli@...iglobal.com> Cc: "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>, Jason Xing <kerneljasonxing@...il.com> Subject: Re: [PATCH net v2] tcp: fix mishandling when the sack compression is deferred 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.
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