Messages in this thread | | | Subject | RE: My vote against eepro* removal | Date | Thu, 19 Jan 2006 11:26:51 +0100 | From | "kus Kusche Klaus" <> |
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> From: Lee Revell > On Thu, 2006-01-19 at 08:19 +0100, kus Kusche Klaus wrote: > > Last time I tested (around 2.6.12), eepro100 worked much better > > in -rt kernels w.r.t. latencies than e100: > > > > e100 caused a periodic latency of about 500 microseconds > > exactly every 2 seconds, no matter what the load on the interface > > was (i.e. even on an idle interface). > > > > eepro100 did not show any latencies that long, it worked much > > smoother w.r.t. latencies. > > > > Of course I would prefer to have e100 fixed over keeping eepro100 > > around forever, but the last time I checked, it still wasn't fixed. > > Please provide latency traces to illustrate the problematic code path.
It's not a "latency": As far as I can tell, interrupts or preemption are not disabled, the latency tracer doesn't show anything.
I just noticed that low-pri rt processes did not get scheduled for about 500 microseconds when e100 was active (even if the net was idle), and that there were no such breaks with eepro100.
I didn't analyze it in detail at that time, I believed that the e100 interrupt handler thread was running every 2 seconds for 500 microseconds, because the interrupt count of eth0 incremented every 2 seconds, exactly when my rt processes paused.
This would be bad: That irq thread is at rt prio 47 on my system, above many importent things.
However, I checked more closely now, and found out that only a small portion of the 500 microseconds is spent in the irq thread. Most of it is spent in the timer thread, at rt prio 1, so the whole thing is a much smaller problem than I originally believed.
Must be the function e100_watchdog.
> It sounds like you have known about this issue for a while, were you > waiting for it to fix itself?
See my other reply: I didn't notice that eepro100 is to be removed, and as long as eepro100 was there, it was no problem for me.
-- Klaus Kusche (Software Development - Control Systems) KEBA AG Gewerbepark Urfahr, A-4041 Linz, Austria (Europe) Tel: +43 / 732 / 7090-3120 Fax: +43 / 732 / 7090-6301 E-Mail: kus@keba.com WWW: www.keba.com
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