On 01.06.2012 19:24, Philip Martin wrote:
> Philip Martin <philip.martin_at_wandisco.com> writes:
>
>> Is COPY_TWO_BYTES a significant optimisation?
> r1325896 implies this is most significant for ra_svn. So I compared the
> testsuite over ra_svn built with the "fast" code and the "slow" code.
> The CPU used by the testsuite and svnserve was:
>
> "fast" code
>
> 749.93user 404.98system 9:09.25elapsed testsuite
> 0:32.43 svnserve
>
> 742.84user 400.00system 8:59.75elapsed testsuite
> 0:32.70 svnserve
>
> 739.51user 400.87system 8:58.91elapsed testsuite
> 0:32.66 svnserve
>
> "slow" code
>
> 745.06user 402.36system 9:04.21elapsed testsuite
> 0:32.73 svnserve
>
> 739.94user 401.86system 8:57.13elapsed testsuite
> 0:32.58 svnserve
>
> On my Linux box this optimisation isn't significant. Perhaps it makes a
> difference on some other platform or with some other test scenario, but
> at the moment it's not clear why we would want with this code.
I can't see how any compiler these days, except possibly one that
targets really tiny embedded platforms, would do worse with memcpy than
with the "optimized" code. I suspect someone has been a bit too eager
with optimizations without actually measuring their impact. :)
-- Brane
Received on 2012-06-02 13:41:32 CEST