Date: Sat, 4 Jun 2005 11:50:05 GMT From: Bruce Evans <bde@zeta.org.au> To: freebsd-bugs@FreeBSD.org Subject: Re: kern/81807: Silo overflows with serial multiport cards Message-ID: <200506041150.j54Bo5ZR035145@freefall.freebsd.org>
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The following reply was made to PR kern/81807; it has been noted by GNATS. From: Bruce Evans <bde@zeta.org.au> To: Bernd Luevelsmeyer <bdluevel@heitec.net> Cc: FreeBSD-gnats-submit@FreeBSD.org, freebsd-bugs@FreeBSD.org Subject: Re: kern/81807: Silo overflows with serial multiport cards Date: Sat, 4 Jun 2005 21:44:14 +1000 (EST) On Thu, 2 Jun 2005, Bernd Luevelsmeyer wrote: >> Description: > The machine has 3 serial 8-port-cards installed, 2 of them ISA cards > and one PCI card. The card model of all 3 of them is Moxa SmartIO > C168H (http://www.moxa.com/Product/C168H.htm and > http://www.moxa.com/Product/C168HPCI.htm). Since Upgrading to > 5-Stable the ISA cards have high numbers of silo overflows. This did > not happen with 4-Stable. > The overflows happened with SCHED_4BSD or SCHED_ULE, with and > without PREEMPTION in the kernel, and regardless of baudrate (I > tried 9600 and 115200). Also I tried several HZ values in the kernel > (100, 1000 and 4000), and it didn't matter. > > The machine is a PII with 300 MHz. Now this isn't the most powerful > (and ISA is a little bit old-fashioned), but the effect happens also > when only one of the 24 ports is used and it's at 9600 Baud, and > anyway with 4-Stable there was no problem at all. Interrupt handling is bad in -current but not usually that bad. The loss of performance was in the 5-10% range when I tested it a lot on a 366 MHz Celeron 12-18 months ago. Latency increase is worse than performance decrease but wasn't noticeable with <= 8 ports at 115200. > Here is the machine's dmesg: Everything seems to be set up correctly. sio even handles the isa ports better that the pci ports. I would have expected silo overflows to occur for the pci ports first because fast interrupts are not used for them (try using the PUC_FASTINTR option to fix this). Interrupts seem to be working at probe time. Do they work later? Use vmstat or systat -v to check that some keep occurring. Check that fast interrupts are used by booting with -v. Bruce
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