Re: [RFC][PATCH] linux-2.4.21-pre4_tsc-lost-tick_A0

[george anzinger <george@mvista.com>]

john stultz wrote:
> 
> On Thu, 2003-01-30 at 17:08, george anzinger wrote:
> > john stultz wrote:
> > > I'm already somewhat cautious that loops_per_jiffy isn't going to cut it
> > > with this patch (I'm thinking fast_gettimeoffset_quotient would probably
> > > be better). So please let me know if you find any issues with this
> > > patch.
> >
> > I think you are wondering about the "/", as am I.  Possibly
> > a while loop, or, something like
> > fast_gettimeoffset_quotient, but scaled to do jiffies
> > instead of micro seconds.  Still you SHOULD be doing this so
> > seldom that one wonders if the "/" is all that bad.
> 
> Yea, I'm assuming it would be rare enough that the div won't be too much
> of a performance drop and would make the code more clear. Although if it
> is a concern I'm not opposed to speeding it up.
> 
> > Another thing, possibly not so easily fixed given the
> > division between "arch" code and common code, but I would
> > like to see jiffies updated in only ONE place.  With this
> > patch it is updated in .../kernel/timer.c AND in
> > .../arch/kernel/time.c.  In the high-res-timers patch I made
> > the jiffies update an inline in an "arch" header file so I
> > could have the best of both worlds, i.e. update from common
> > code using arch resources (TSC, etc).
> 
> Yea, I'm not psyched about that as well (not only is it updated twice,
> but three times: arch independent, tsc and cyclone). The inline bit
> sounds interesting, are you planning on pushing that in?

I am a bit discouraged on that front.  I was hoping to get
the POSIX clocks & timers patch in, but it is long past
Halloween and, while he said he might, he didn't.  I don't
know if he is finished as yet, but...  The jiffies update
was part of the core patch to do the high res timers which
he said he would not take.  I would like to try parting it
out and pushing in some stuff, such as scmath.h which makes
things like fast_gettimeoffset_quotient not only
understandable but easy.  Folks in the cpu frequency area
would like that.  Still, my boss has other plans...

-- 
George Anzinger   george@mvista.com
High-res-timers: 
http://sourceforge.net/projects/high-res-timers/
Preemption patch:
http://www.kernel.org/pub/linux/kernel/people/rml