René Scharfe <rene.scharfe@xxxxxxxxxxxxxx> writes:
> Am 17.05.2012 01:31, schrieb Øyvind A. Holm:
>> On Debian GNU/Linux 6.0.5 (squeeze), the two commits on the
>> tr/xdiff-fast-hash branch introduces compiler warnings and breaks
>> t/t0020-crlf.sh and maybe later tests:
>
> What does the following short C program report when run (e.g. put it
> in a file named s.c, then run "gcc -o s s.c" and "./s")?
>
> #include <stdio.h>
> int main(int argc, const char **argv) {
> printf("%u %u %u\n", sizeof(int), sizeof(long), sizeof(void *));
> return 0;
> }
>
> I suspect you run a 32-bit userland on a 64-bit kernel.
>
> On Ubuntu 12.04 x86, t0020 fails for me as well when I compile with
> XDL_FAST_HASH explicitly set (it's off by default).
OK. So does that indicate at least breakage in the Makefile that
attempts to set XDL_FAST_HASH only on x86_64, mistakenly triggering
on Øyvind's x86 32-bit userland, or did Øyvind manually flipped the
feature on?
It is a separate issue that XDL_FAST_HASH code does not work on 32-bit
systems, even though it is advertised that it only needs to be on
little-endian.
> It succeeds after reverting 6f1af02, though, strangely enough.
It is strange. I do not see anything glaringly wrong in the conversion
in that commit. The only difference I see is that count_masked_bytes in
the original used to take unsigned long on 64-bit archs but the updated
one takes signed long, but that on 32-bit archs the function takes
signed long in both versions so it cannot be it. Stumped...
> Also, here are the measurements for master (v1.7.10.2-520-g6a4a482)
> without XDL_FAST_HASH, and with master minus 6f1af02 plus explicitly
> set XDL_FAST_HASH:
>
> Test master reverted+FAST
> ---------------------------------------------------------------------
> 4000.1: log -3000 (baseline) 0.08(0.05+0.02) 0.08(0.05+0.02)
> 4000.2: log --raw -3000 (tree-only) 0.39(0.34+0.04) 0.39(0.32+0.06)
> 4000.3: log -p -3000 (Myers) 1.55(1.43+0.11) 1.43(1.29+0.12)
> 4000.4: log -p -3000 --histogram 1.63(1.51+0.10) 1.50(1.35+0.14)
> 4000.5: log -p -3000 --patience 1.85(1.71+0.13) 1.73(1.62+0.10)
So the patch does give us slight performance edge, when it works ;-)
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