On Fri, Nov 27, 2020 at 2:20 AM Tom Lane <t...@sss.pgh.pa.us> wrote: > Alexander Korotkov <aekorot...@gmail.com> writes: > > On Thu, Nov 26, 2020 at 1:32 PM Heikki Linnakangas <hlinn...@iki.fi> wrote: > >> Is there some official ARM documentation, like a programmer's reference > >> manual or something like that, that would show a reference > >> implementation of a spinlock on ARM? It would be good to refer to an > >> authoritative source on this. > > > I've compared assembly output of gcc implementations of CAS and TAS. > > FWIW, I see quite different assembly using Apple's clang on their M1 > processor. What I get for SpinLockAcquire on HEAD is (lock pointer > initially in x0):
Yep, arm v8.1 implements single-instruction atomic operations swpal and casa, which much more look like x86 atomic instructions rather than loops of ldxr/stlxr. So, all the reasoning upthread shouldn't work here, but the advantage is much more huge. ------ Regards, Alexander Korotkov
