Re: [PATCH] New x86_64 time code for 2.5.70

[Vojtech Pavlik <vojtech@ucw.cz>]

On Wed, Jun 11, 2003 at 05:33:55PM -0700, john stultz wrote:
 
> This patch applies on top of Bryan's patch, and solves the major time
> inconsistencies I was seeing earlier. I don't like that I still have to
> have the sanity check on offset to ensure it doesn't go negative
> (frequently I get offsets of -1),

IMO this is to be expected and not a problem. In the case of offset of
'-1' the time will jump one usec forward on the timer interrupt, but
that's harmless and nothing worse should happen.

> and that along with the fact that I'm
> seeing a steady drift forward on every kernel I've run (2.4/2.5) makes
> me think that the timer interrupt frequency may be a bit higher then we
> intend. Might just be the dev hardware I'm running on, though.

The devel hardware's RTC crystals are quite a bit off the correct
frequency, but still in the range fixable by NTP.

> I'm also got some cleanup changes I'd like to make, but I'll wait until
> after things work to polish that stuff up. 
> 
> Let me know if you have any issues with this patch. 

Looks OK to me.

> thanks
> -john
> 
> diff -Nru a/arch/x86_64/kernel/time.c b/arch/x86_64/kernel/time.c
> --- a/arch/x86_64/kernel/time.c	Wed Jun 11 17:28:07 2003
> +++ b/arch/x86_64/kernel/time.c	Wed Jun 11 17:28:07 2003
> @@ -254,11 +254,14 @@
>  		vxtime.last = offset;
>  	} else {
>  		offset = (((tsc - vxtime.last_tsc) *
> -			   vxtime.tsc_quot) >> 32) - tick_usec;
> +			   vxtime.tsc_quot) >> 32) - (USEC_PER_SEC/HZ);
> +		/* sanity check on offset */
> +		if(offset < 0)
> +			offset = 0;
>  
> -		if (offset > tick_usec) {
> -			lost = offset / tick_usec;
> -			offset %= tick_usec;
> +		if (offset > (USEC_PER_SEC/HZ)) {
> +			lost = offset / (USEC_PER_SEC/HZ);
> +			offset %= (USEC_PER_SEC/HZ);
>  		}
>  
>  		vxtime.last_tsc = tsc - vxtime.quot * delay / vxtime.tsc_quot;
> @@ -275,10 +278,7 @@
>  			       "tick(s)! (rip %016lx)\n",
>  			       (offset - vxtime.last) / hpet_tick - 1,
>  			       regs->rip);
> -		// XXX The accounting of lost ticks is way off right
> -		// now. -bos
> -
> -		// jiffies += lost;
> +		jiffies += lost;
>  	}
>  
>  /*
> 
> 
> 

-- 
Vojtech Pavlik
SuSE Labs, SuSE CR