Am 07.11.2015 um 20:36 schrieb drago01:
On Sat, Nov 7, 2015 at 7:40 PM, Reindl Harald <h.reindl@xxxxxxxxxxxxx> wrote:the point is compile a single application with new features won#t gain that muc 8until you do the same with most libraries used by the software) but having the whole distribution is a summary with a completly different behavior than a single test of software xyzUh no you just have to compile the software any libraries used by the hot paths of the software you are trying to test.
for which one? that don't show the impact on a complete distribution anyways
if there would be no difference kernel upstream won't invest that much time for runtime-cpu-detection (look at the bootlog on different hardware) here are examples http://www.phoronix.com/scan.php?page=news_item&px=MTU0MTY http://www.phoronix.com/scan.php?page=news_item&px=MTI1NjcYou missed the point completely. 1. AVX != (S)SSE3
i know that
There are lots of workloads that would benefit from AVX but SSE3 doesn't add that much (enabling SSE2 on i686 would gain you more for instance).
enable SSE3 don't diable SSE2 so "gain you more" is impossible
2. Runtime detection does not have the cost of dropping support for specific hardware
runtime detection needs to be implemented in every relevant software at it's own and hence has a *high cost*
add -msse3 to the default falgs have no costs at all but only an impact of a unknown amount f *very* outdated hardware which is unlikely running a bleeding edge distribution
frankly whatever somebody has run on a 10 years old machine can be easily virtualized and i doubt that many people have a 10 years old computer as their only device, as far there is something with a core2 or newer in the house you can virtualize the other machine and save a lot of energy
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