Date: Thu, 27 Jan 2000 20:57:06 -0700 From: Warner Losh <imp@village.org> To: Juergen Lock <nox@jelal.kn-bremen.de> Cc: freebsd-stable@FreeBSD.ORG Subject: Re: Warner's PCI Modem Driver Message-ID: <200001280357.UAA51783@harmony.village.org> In-Reply-To: Your message of "Fri, 28 Jan 2000 04:26:15 %2B0100." <200001280326.EAA15051@saturn.kn-bremen.de> References: <200001280326.EAA15051@saturn.kn-bremen.de> <Pine.LNX.3.96.1000127082044.30216B-100000@mail.clones.com>
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In message <200001280326.EAA15051@saturn.kn-bremen.de> Juergen Lock writes: : They perform better?? shouldn't the isa bus' bandwidth be more : than enough for the (even compressed) 56kbps of a modem? We've found that we get better ping times (about 10% faster)[*], fewer dropped characters due to interrupt latency[**] and the system seems a little snappier[***]. We've also measured a 5% increase in ftp performance on the usual ftp a big honkin' file.[****] These tests were performed on an AMD 5x86 133 based machine (a 486 class machine running at a 33MHz bus). The old ISA modems were US Robotics Sportsters while the new PCI modem was the ActionTec FAX Modem (don't know what they called this in their released version, since this was a preliminary one). We have about 50-100 firewall rules (same ruleset for both runs, we've changed it since the tests I performed, so I don't have an exact number). The remove modem was a US Robotics sportster internal ISA modem. On the ISA based modems, we'd see about 10 dropped character events a day when traffic got heavy. We have two 33.6 connections on this machine. With the PCI modems, we see about 1 a week. My guess is that we're running right on the harry edge of needing more CPU power and the lower PCI latency and faster bus response makes the difference here. So it isn't a huge win (you won't get 2x the performance), but it did allow us to make our under powered machine last a few more months while we saved for larger iron to replace it and two other machines with (mostly to consolidate rack space given today's insanely inexpensive machines). While one external modem vs 1 internal modem may be a no brainer, it gets really hairy when you have 5 or 6 external modems, each with their own wall wort. Those wall worts eat powerstrip real estate like you wouldn't believe. Warner [*] 170ms vs 140ms, which is more like 20% is what I'm measuring now on a mixed machine (we just brought up a new member and haven't converted him to a new pci modem yet) right now. I seem to recall it went from 160ms to 140ms [**] Haven't seen a buffer overflow since Dec 2 with the sio. Before we'd see 10 messages a day of xxx more interrupt-level buffer overflows. These were worst when large transfers were happening during daily or weekly running. [***] Purely subjective [****] Typical ftp the kernel to /dev/null over the link 3 times, average rates and compare before/after. I can no longer find the numbers to back up this claim, and I don't have an account on the other end of new client to test it out via the same machine. To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe freebsd-stable" in the body of the message
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