RE: [patch] prefer TSC over PM Timer

[Mikael Pettersson <mikpe@csd.uu.se>]

dean gaudet writes:
 > On Tue, 16 Nov 2004, Pallipadi, Venkatesh wrote:
 > 
 > > I think trying to remove repeated inl()'s in read_pmtmr is a better 
 > > fix for this issue. As John mentioned in other thread, we should do 
 > > repeated reads only when something looks broken. Not always.
 > 
 > that would be a nice improvement... then timer_pm will only be 3x as slow 
 > as timer_tsc instead of 10x slower :)  it's still a lot of unnecessary 
 > overhead for many systems, and unfortunately this is a real performance 
 > problem (albeit exaggerated by code which is overzealous in its use of 
 > gettimeofday()).
 > 
 > on a tangent... has the local apic timer ever been considered?  it's fixed 
 > rate, and my measurements show it in the same performance ballpark as TSC.
 > 
 > i know that all p3, p-m, p4, k8 and efficeon have local APIC, but i'm not 
 > sure if k7 (other than k7 smp parts of course) have local apics... so i'm 
 > not sure how widespread it is compared to pm-timer.

All K7/K8s except the very first K7 Model 1 have local APICs.
There is no difference between UP and MP parts in this respect.

/Mikael