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    SubjectRe: ext3 performance inconsistencies, 2.4/2.6

    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++)

    and then just time it.

    I get:

    torvalds@home:~> time ./a.out > /dev/null

    real 0m1.305s
    user 0m1.283s
    sys 0m0.004s


    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


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