Date: Tue, 13 Oct 1998 15:41:01 +1000 From: Bruce Evans <bde@zeta.org.au> To: brian@Awfulhak.org, kjc@csl.sony.co.jp Cc: current@FreeBSD.ORG Subject: Re: Improper sharing of modem bandwidth Message-ID: <199810130541.PAA12787@godzilla.zeta.org.au>
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>Surely, once the packet queueing delay is reduced, we need to reduce >the tty delay. The current kernel doesn't have ioctls for the >buffer size but slip uses a smaller tty buffer and has a better >response time than ppp. User ppp is behind a _lot_ of output buffering, including (at speeds >= 57600 Kbps) a 4KB tty buffer (up from 2KB in FreeBSD-2.2). Perhaps the increase from 2KB to 4KB is especially significant when the MTU is 1500. Kernel ppp doesn't have this problem. Kernel ppp also has a fast path for incoming packets to avoid the average 5ms latency for polling the pseudo-DMA input buffer. This only seems to be important for local connections. Bruce To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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