Messages in this thread | | | Date | Tue, 4 Nov 2003 14:31:18 -0800 (PST) | From | Linus Torvalds <> | Subject | Re: ext3 performance inconsistencies, 2.4/2.6 |
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On Tue, 4 Nov 2003, Ulrich Drepper wrote: > > I don't see any verison numbers mentioned. If you want to benchmark > NPTL use the recent code, e.g., from Fedora Core 1 or RHEL3. Nothing > else makes any sense since there have mean countless changes since the > early releases.
This is actually _really_ trivial to see with a simple test program.
This is Fedora Core test3:
#include <stdlib.h>
/* Change this to match your CPU */ #define NR (10*1000*1000)
int main(int argc, char **argv) { int i; for (i = 0; i < NR; i++) putchar(0); }
and then just time it.
I get:
torvalds@home:~> time ./a.out > /dev/null
real 0m1.305s user 0m1.283s sys 0m0.004s
and
torvalds@home:~> time LD_ASSUME_KERNEL=2.4.1 ./a.out > /dev/null real 0m0.321s user 0m0.318s sys 0m0.003s
ie a factor of _four_ difference in the speed of "putchar()".
Interestingly, if I compile the program statically, I don't see this effect, and it's noticeably faster still:
torvalds@home:~> gcc -O2 -static test.c torvalds@home:~> time ./a.out > /dev/null
real 0m0.193s user 0m0.191s sys 0m0.002s
torvalds@home:~> time LD_ASSUME_KERNEL=2.4.1 ./a.out > /dev/null
real 0m0.194s user 0m0.190s sys 0m0.004s
Is the TLS stuff done through an extra dynamically loaded indirection or something?
Linus
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