Date: Thu, 25 Jan 2001 11:14:03 -0600 (CST) From: Jonathan Lemon <jlemon@flugsvamp.com> To: wollman@khavrinen.lcs.mit.edu, net@freebsd.org, jayanth@freebsd.org Subject: Re: I have delayed ACK problems Message-ID: <200101251714.f0PHE3L73868@prism.flugsvamp.com> In-Reply-To: <local.mail.freebsd-net/200101251617.LAA83006@khavrinen.lcs.mit.edu> References: <local.mail.freebsd-net/77394.980367750@winston.osd.bsdi.com> <local.mail.freebsd-net/Pine.BSF.4.21.0101250840280.48291-100000@besplex.bde.org> <local.mail.freebsd-net/20010125002509.A77051@yahoo-inc.com>
next in thread | previous in thread | raw e-mail | index | archive | help
In article <local.mail.freebsd-net/200101251617.LAA83006@khavrinen.lcs.mit.edu> you write: ><<On Thu, 25 Jan 2001 00:25:10 -0800, jayanth <jayanth@yahoo-inc.com> said: > >> could you test this patch and compare the results. >> By generating an ACK for every segment with the TH_PSH flag set >> I found a significant increase in throughput. > >I don't think this is right. > >I think what we want to do is: > > if (callout_pending(tp->tt_delack)) { > callout_stop(tp->tt_delack); > tp->t_flags |= TF_ACKNOW; > } else > callout_reset(...) I'm not sure this is required. Expanding the context of the area in question: /* * Add data to socket buffer. */ m_adj(m, drop_hdrlen); /* delayed header drop */ sbappend(&so->so_rcv, m); sorwakeup(so); if (tcp_delack_enabled) { callout_reset(tp->tt_delack, tcp_delacktime, tcp_timer_delack, tp); } else { tp->t_flags |= TF_ACKNOW; tcp_output(tp); } return; From the bottom portion of tcp_output(): tp->last_ack_sent = tp->rcv_nxt; tp->t_flags &= ~TF_ACKNOW; if (tcp_delack_enabled) callout_stop(tp->tt_delack); So simply setting TF_ACKNOW and calling tcp_output should be sufficient; if there is a pending delack timer it will get turned off when the ACK is actually sent. I think that jayanth's patch is correct, although I slightly dislike tying it to the PSH flag - not all implementations actually set this. However, it is better than the lower bound of acking every incoming data packet. -- Jonathan To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-net" in the body of the message
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?200101251714.f0PHE3L73868>