From mboxrd@z Thu Jan 1 00:00:00 1970 From: Eric Dumazet Subject: Re: [PATCH net-next 3/4] tcp: add SACK compression Date: Thu, 17 May 2018 08:46:26 -0700 Message-ID: References: <20180517121213.43559-1-edumazet@google.com> <20180517121213.43559-4-edumazet@google.com> <58bcf9c0-e4f0-691d-8d6a-40ff3629f500@gmail.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Cc: David Miller , Netdev , =?UTF-8?Q?Toke_H=c3=b8iland-J=c3=b8rgensen?= , Yuchung Cheng , Soheil Hassas Yeganeh To: Neal Cardwell , Eric Dumazet Return-path: Received: from mail-pl0-f66.google.com ([209.85.160.66]:38583 "EHLO mail-pl0-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751047AbeEQPq2 (ORCPT ); Thu, 17 May 2018 11:46:28 -0400 Received: by mail-pl0-f66.google.com with SMTP id c11-v6so2788887plr.5 for ; Thu, 17 May 2018 08:46:27 -0700 (PDT) In-Reply-To: <58bcf9c0-e4f0-691d-8d6a-40ff3629f500@gmail.com> Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: On 05/17/2018 08:40 AM, Eric Dumazet wrote: > > > On 05/17/2018 08:14 AM, Neal Cardwell wrote: >> Any particular motivation for the 2.5ms here? It might be nice to match the >> existing TSO autosizing dynamics and use 1ms here instead of having a >> separate new constant of 2.5ms. Smaller time scales here should lead to >> less burstiness and queue pressure from data packets in the network, and we >> know from experience that the CPU overhead of 1ms chunks is acceptable. > > This came from my tests on wifi really :) > > I also had the idea to make this threshold adjustable for wifi, like we did for sk_pacing_shift. > > (On wifi, we might want to increase the max delay between ACK) > > So maybe use 1ms delay, when sk_pacing_shift == 10, but increase it if sk_pacing_shift has been lowered. > > BTW, maybe my changelog or patch is not clear enough : As soon as some packets are received in order, we send an ACK, even if the timer was armed. (This is the beginning of __tcp_ack_snd_check()) When this ACK is sent, timer is canceled (in tcp_event_ack_sent())