By: Linus Torvalds (torvalds.delete@this.linux-foundation.org), July 11, 2013 10:20 am
Room: Moderated Discussions
Linus Torvalds (torvalds.delete@this.linux-foundation.org) on July 11, 2013 10:57 am wrote:
>
> No sane person uses NEON, because NEON isn't available in most ARM implementations.
Side note: this is where virtual machines can help: JIT'ing to whatever is the underlying hardware model. At the same time, JITs are particularly bad at things like vectorization for anything but the simplest possible case unless the VM itself has some kind of vector model. It's just really hard to vectorize things without lots of contextual information.
But for a "native code" benchmark, I still claim that disabling NEON is actually the sane thing to do given the current (and near-future) ARM situation.
In contrast, using SSE on x86 makes sense, because it's universally available. So the people here screaming "x86 uses SSE, but ARM doesn't use NEON - unfair" don't really understand the issues, and are just making braying noises.
None of that makes AnTuTu a better benchmark, though. Microbenchmarks that don't do real work are universally crap. Of course, the ARM people shouldn't really complain - they've been using those kinds of pointless benchmarks for decades, and continue to do so (google for "dhrystone MIPS" - there are ARM people who use that crap still, and Wilco used to quote it religiously not that long ago)
Linus
>
> No sane person uses NEON, because NEON isn't available in most ARM implementations.
Side note: this is where virtual machines can help: JIT'ing to whatever is the underlying hardware model. At the same time, JITs are particularly bad at things like vectorization for anything but the simplest possible case unless the VM itself has some kind of vector model. It's just really hard to vectorize things without lots of contextual information.
But for a "native code" benchmark, I still claim that disabling NEON is actually the sane thing to do given the current (and near-future) ARM situation.
In contrast, using SSE on x86 makes sense, because it's universally available. So the people here screaming "x86 uses SSE, but ARM doesn't use NEON - unfair" don't really understand the issues, and are just making braying noises.
None of that makes AnTuTu a better benchmark, though. Microbenchmarks that don't do real work are universally crap. Of course, the ARM people shouldn't really complain - they've been using those kinds of pointless benchmarks for decades, and continue to do so (google for "dhrystone MIPS" - there are ARM people who use that crap still, and Wilco used to quote it religiously not that long ago)
Linus
