Date: Sat, 1 May 2004 21:41:27 +1000 (EST) From: Bruce Evans <bde@zeta.org.au> To: Burkard Meyendriesch <bm@malepartus.de> Cc: othermark <atkin901@yahoo.com> Subject: Re: sio: lots of silo overflows on Asus K8V with Moxa Smartio C104H/PCI solved Message-ID: <20040501212314.N20783@gamplex.bde.org> In-Reply-To: <20040501102705.7a7ec726.bm@malepartus.de> References: <20040426111754.38a855c4.bm@malepartus.de> <20040426233925.Y5300@gamplex.bde.org><c6u3nd$f8q$1@sea.gmane.org> <20040501102705.7a7ec726.bm@malepartus.de>
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On Sat, 1 May 2004, Burkard Meyendriesch wrote:
> On Fri, 30 Apr 2004 10:51:41 -0700 othermark wrote:
> ...
> > so try the following in your kernel and rebuild
> >
> > options COM_MULTIPORT
> > options PUC_FASTINTR
> >
> > device apic
> >
> Thanks for the hint, this solves my problem. I now have a constant
> char input flow rate of about 11000 chars/s at 115200 bps. This
> makes an average interupt rate of 1400 ints/s, so each interrupt
> service gets about 8 input chars of the silo. With a 16[45]50 silo
Oops, I used a factor of 14 in some other calculations. Someone
reduced the fifo trigger level from 14 (2 below the top) to 8. If
the interrupt latency is significantly less than 1 character time,
then the interrupt handler will always see precisely 8 characters
of input per receiver interrupt for sustained input. Conversely,
we can determine whether there is significant latency from very
careful measurements of the number of characters per receiver
interrupt.
> size of 16 chars this seems to be a reasonable rate. All the silo
> overflow warnings disappeared.
So there must be something holding Giant for too long, and if my other
patch doesn't help then there must also be a thread with priority
higher than PI_TTYLOW that runs for too long. This doesn't seem to
be much of a problem in my local configurations, so you can test fixes
and workarounds for it better than me. Try the following untested
hack to get higher priority than most threads:
%%%
Index: sio.c
===================================================================
RCS file: /home/ncvs/src/sys/dev/sio/sio.c,v
retrieving revision 1.428
diff -u -2 -r1.428 sio.c
--- sio.c 30 Apr 2004 21:16:52 -0000 1.428
+++ sio.c 1 May 2004 11:29:44 -0000
@@ -1164,5 +1302,6 @@
if (ret) {
ret = BUS_SETUP_INTR(device_get_parent(dev), dev,
- com->irqres, INTR_TYPE_TTY,
+ com->irqres,
+ INTR_TYPE_CLOCK | INTR_MPSAFE,
siointr, com, &com->cookie);
if (ret == 0)
%%%
This is a superset of the previous patch.
> Btw, "device apic" doesn't exist; did you mean "device acpi"?
They both exist in -current. "device apic" is newer.
Bruce
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