Date: Wed, 04 Mar 1998 20:40:42 -0800 (PST) From: Simon Shapiro <shimon@simon-shapiro.org> To: Mike Smith <mike@smith.net.au> Cc: Evan Champion <evanc@synapse.net>, current@FreeBSD.ORG, Matthew Thyer <Matthew.Thyer@dsto.defence.gov.au> Subject: Re: silo overflows (Was Re: 3.0-RELEASE?) Message-ID: <XFMail.980304204042.shimon@simon-shapiro.org> In-Reply-To: <199803050323.TAA23786@dingo.cdrom.com>
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On 05-Mar-98 Mike Smith wrote: ... > Interrupt rate is less significant in this issue than interrupt > latency. At 230kbps you have about 43us/character. Without a 16650 > datasheet I can't confirm whether the standard FIFO trigger levels are > doubled or not; if they are, you have 4 bytes or about 170us between > when the interrupt is generated and "too late". That means that the built-in fifo should go down from 14 to 12 bytes, or probably 10. Does the IOCTL that changes baud rate dividers do that too? > Because of the way the sio driver handles interrupts, you want to look > for code sections bracketed with disable_intr/enable_intr calls to find > possible culprits. If the driver disables interrupts then loses them, is this like shooting yourself in the foot and complain about the pain? :-) >> Every >> 1KB, you write to disk, so now we have 1,160 interrupts per second. > > There's no guarantee of this; particularly not if I/O clustering, async > or soft updates are enabled. Filesystems are mounted async during an > install. Of course. The purpuse of this napkin computation was to see, crudely, if we have congestion, or not. I think we can easily see that we do, and some overrun control is necessary. I simply do not know enough of the internals of FreeBSD to speculate any further. It has to be a ssoluble problem. We have more MIPS, more bandwidth and more control than a modem has. No? ---------- Sincerely Yours, Simon Shapiro Shimon@Simon-Shapiro.ORG Voice: 503.799.2313 To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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