Re: CURRENT as gateway on not-so-fast hardware: where is a bottlneck?

From: Lev Serebryakov <lev_at_FreeBSD.org>
Date: Wed, 15 Aug 2012 15:11:49 +0400
Hello, Alexander.
You wrote 15 августа 2012 г., 15:07:32:

AM> Yes, that is what I expected to see there. If you have timecounter other
AM> then i8254, you can release i8254 from those duties to allow using it as
AM> one-shot setting hint.attimer.0.timecounter=0. Otherwise there are no 
AM> options now.

% dmesg | grep timer
pmtimer0 on isa0
Event timer "RTC" frequency 32768 Hz quality 0
attimer0: <AT timer> at port 0x40 on isa0
Event timer "i8254" frequency 1193182 Hz quality 100
%

>> (a) with polling, system is responsive under any load, but wire2wifi
>> performance  is hugely affected by wire2wire traffic (and mpd5
>> inbetween). And, yes, "top" seems to lie about idle time.
AM> I don't know why wifi is so different. Suppose it is for some reason
AM> more affected by latencies.
  Adrian says, it is.

>> (b) with interrupts, system works much better when it works (wire2wifi
>> speed is affected by wire2wire traffic, but to much less extent), but
>> it freezes every third minute for minute, when traffic is passed, but
>> no user-level applications including BIND and DHCP server) works at
>> all FOR MINUTE OR MORE. It not looks like 100ms lag, which could affect
>> video playback. It looks like 60-120 seconds lag! At least, in case of
>> ULE, I didn't try 4BSD yet.
AM> In this case problem may be that kernel and interrupt threads are all
AM> having absolute priorities. It means until they release the CPU, 
AM> user-level may get no CPU time at all. :(
 How  could  it  be  seen  in  KTR  traces?  Where could I read how to
decipher and read these traces?

-- 
// Black Lion AKA Lev Serebryakov <lev_at_FreeBSD.org>
Received on Wed Aug 15 2012 - 09:12:02 UTC

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