Re: [RFC][PATCH] Runtime switching of the idle function [take 2]

> But on my system gettimeofday uses the TSC and it's still ~35x slower
> than RDTSC:
> 
> rlrevell@mindpipe:~$ ./timetest 
> rdtsc: 10000 calls in 1079 usecs
> gettimeofday: 10000 calls in 36628 usecs

First if you run this on an Athlon 64 the measurement is likely
wrong because RDTSC can be speculated around. To get accurate
data you need to add synchronizing instructions.

Then you're likely running 32bit. It doesn't use vsyscall gettimeofday
yet, which makes it slower. 64bit would.

-Andi

-
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/

Follow-Ups:
- Re: [RFC][PATCH] Runtime switching of the idle function [take 2]
  - From: Lee Revell <[email protected]>

References:
- RE: [RFC][PATCH] Runtime switching of the idle function [take 2]
  - From: "Brown, Len" <[email protected]>
- Re: [RFC][PATCH] Runtime switching of the idle function [take 2]
  - From: Andi Kleen <[email protected]>
- Re: [RFC][PATCH] Runtime switching of the idle function [take 2]
  - From: Lee Revell <[email protected]>
- Re: [RFC][PATCH] Runtime switching of the idle function [take 2]
  - From: Andi Kleen <[email protected]>
- Re: [RFC][PATCH] Runtime switching of the idle function [take 2]
  - From: Lee Revell <[email protected]>

Prev by Date: Re: [discuss] Re: [Perfctr-devel] Re: Enabling RDPMC in user space by default
Next by Date: Re: Linux 2.6.15-rc3
Previous by thread: Re: [RFC][PATCH] Runtime switching of the idle function [take 2]
Next by thread: Re: [RFC][PATCH] Runtime switching of the idle function [take 2]
Index(es):
- Date
- Thread

[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]