Date: Wed, 04 Mar 1998 20:44:12 -0800 From: Mike Smith <mike@smith.net.au> To: shimon@simon-shapiro.org Cc: Mike Smith <mike@smith.net.au>, 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: <199803050444.UAA24238@dingo.cdrom.com> In-Reply-To: Your message of "Wed, 04 Mar 1998 20:40:42 PST." <XFMail.980304204042.shimon@simon-shapiro.org>
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> > 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? No. Actually, I went looking (in vain *^%*&^%*) for the code that plays with the sio FIFOs. I think I'm going blind. 8( > > 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? :-) In this case, it's someone else shooting the driver in the foot. As Bruce pointed out, busmaster DMA is a concern. > 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? Yes, yes, no and also we have less determinism. -- \\ Sometimes you're ahead, \\ Mike Smith \\ sometimes you're behind. \\ mike@smith.net.au \\ The race is long, and in the \\ msmith@freebsd.org \\ end it's only with yourself. \\ msmith@cdrom.com To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-current" in the body of the message
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