Hi, On 05/01/2011 09:56 AM, David Timms wrote: > On 01/05/11 17:41, Hans de Goede wrote: >> Erm, specifying a minimum support CPU in the package description is >> not acceptable IMHO. The fix here is to patch the packages buildsystem, >> so that it gets build for the minimum cpu level which is supported by >> Fedora, and thus will work out of the box on all systems Fedora >> supports. > Where is that stated currently, and for older releases ? > I was hoping someone who knows the exact answer knows... All I can give you is: http://docs.fedoraproject.org/en-US/Fedora/13/html/Release_Notes/index.html#sect-Release_Notes-Hardware_Requirements Which is not really exact... >> No tricks / hacks with multiple compilation, cpu detect scripts, etc. >> will be necessary then. > Though it comes at the cost of audio lag/latency increase when we are > trying to achieve near real time (eg live guitar input to sound effect > generation output). Even on the my machine (4x core amd 3Ghz), the > calculations the app performs for difficult presets (convolution) can > cause jack to abort because rakarrack didn't finish it's calculations > before it was required to deliver data. > > Should I be suggesting to upstream to attempt to detect CPU before > running non-available instructions, eg as part of app startup ? > Can that even be done (reliably) ? As already answered by others ideal would be one binary, which runtime chooses between normal C and mmx/sse#/whatever variants based on CPU capabilities. This is definitely something to ask to upstream, as this won't be trivial. In the mean time, you need to patch the build-system so that you can control what cpu features it will enable, then you can build a number of variants, install them as /usr/libexec/%{name}-$cpufeaturepostfix And make /usr/bin/%{name} a shell script which checks /cpu/procinfo for features and then executes the right binary (passing through all cmdline args using the "$@" magic var for proper quoting) For which variants it makes sense to build, you would need to talk to someone who is more of a cpu head then me, try starting a new thread, with an appropriate $subject. Note that all of this is only really needed on 32 bits, on 64 bit I believe (*) all cpu's have at least sse2, so unless you want to use sse3 you'll only need 1 binary there. Which brings us to a simpler alternative, build a no cpu specific optimizations 32 bit version and use sse2 on x86_64, which is nice and simple. You could then add a README.fedora advising people to use the 64 bit version. Regards, Hans *) Still no CPU head, better verify this with someone who is. -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx https://admin.fedoraproject.org/mailman/listinfo/devel
