Date: Thu, 20 Nov 2003 16:15:19 -0500 From: Don Bowman <don@sandvine.com> To: 'Avleen Vig' <lists-freebsd@silverwraith.com>, Don Bowman <don@sandvine.com> Cc: freebsd-hackers@freebsd.org Subject: RE: Device polling, with SMP? Message-ID: <FE045D4D9F7AED4CBFF1B3B813C85337035E3E7C@mail.sandvine.com>
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From: Avleen Vig [mailto:lists-freebsd@silverwraith.com] > On Thu, Nov 20, 2003 at 12:58:58PM -0500, Don Bowman wrote: > > > I read Luigi's paper at info.iet.unipi.it/~luigi/polling/ > which at the > > > end implies that DEVICE_POLLING on an SMP box might not make > > > sense - but > > > right now for me it would make sense as both CPU's are locked: > > > One tries to handle interrupts > > > The other tries to manage the application > > > > > > I could try forcing DEVICE_POLLING to compile as is > suggested in that > > > URL but I wanted to see if anyone had tried this before. > > > The interface is an FXP. > > > > We use it on em. I just commented out the #error line that > > says you can't do it. > > device polling in idle doesn't work, and the user/system time > > calculation isn't correct, but it works well otherwise. > > This is pretty much what I wanted to confirm thanks! > In which way is the system/user time incorrect? Always, or only under > high load? what about it is incorrect? My skills are limited > but I might > take a stab at fixing that. Well, on -STABLE, there can be only one CPU active in the kernel. Thus on a 2-way HTT system, the system thinks there are 4 processors, but there is no way to get 'system' cpu to exceed 25%. So in polling, the 'user frac' and 'kernel frac' are very difficult to understand. --don
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