On Tue, 2005-11-29 at 10:29 -0800, John Reiser wrote:
> Andi Kleen wrote:
> > I think it's also a useful convention - RDTSC is becomming more and more
> > useless and you cannot expect user applications who just want to
> > measure some cycles to rely on ever changing instable or non existing
> > performance counter APIs.
>
> Users are even more unhappy with ever-changing ABIs -- such as the
> kernel taking away RDTSC.
>
> RDTSC+perfctr [Pettersson] still is the fastest way for user-mode code
> to count something that is highly correlated with both "billable"
> CPU time and "code quality" for a fixed task. With a little care
> RDTSC is close enough to monotonic that I find it very useful.
> Please don't take away user-mode RDTSC.
>
The kernel didn't take this away, the hardware vendors did. For years
although it was risky on paper it was perfectly usable as a cheap high
res timer. I agree that it's unfortunate.
Lee
-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to [email protected]
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
[Index of Archives]
[Kernel Newbies]
[Netfilter]
[Bugtraq]
[Photo]
[Stuff]
[Gimp]
[Yosemite News]
[MIPS Linux]
[ARM Linux]
[Linux Security]
[Linux RAID]
[Video 4 Linux]
[Linux for the blind]
[Linux Resources]
