Re: Can we drop upstream Linux x32 support?

On Tue, Dec 11, 2018 at 9:40 AM Linus Torvalds
[off-list ref] wrote:

On Mon, Dec 10, 2018 at 5:23 PM Andy Lutomirski [off-list ref] wrote:

quoted

I'm seriously considering sending a patch to remove x32 support from
upstream Linux.  Here are some problems with it:

I talked to Arnd (I think - we were talking about all the crazy ABI's,
but maybe it was with somebody else) about exactly this in Edinburgh.

Apparently the main real use case is for extreme benchmarking. It's
the only use-case where the complexity of maintaining a whole
development environment and distro is worth it, it seems. Apparently a
number of Spec submissions have been done with the x32 model.

I'm not opposed to trying to sunset the support, but let's see who complains..

I'm just a single user. I do rely on it though, FWIW.

I hadn't finished my benchmarking in Edinburgh, but for my new machine
that does kernel builds 24/7, I ended up going with x32 userspace (in
a container).

Main reason is that it's a free ~10% improvement in runtime over
64-bit. I.e. GCC-as-a-workload is quite a bit faster as x32,
supposedly mostly due to smaller D cache footprints (I ran out of
cycles to tinker with back and forth perf data collection and settled
down on just running it).

Running classic 32-bit (i386? i686? whatever it's called) is about
half as good. I.e. even then I get a ~5% performance win. Less than
x32, but still better than 64-bit userspace.


-Olof