Re: lockref scalability on x86-64 vs cpu_relax
From: Linus Torvalds <torvalds@linux-foundation.org>
Date: 2023-01-13 00:46:19
Also in:
linux-arch, linux-fsdevel, linuxppc-dev
On Thu, Jan 12, 2023 at 6:31 PM Luck, Tony [off-list ref] wrote:
There's not much "simultaneous" in the SMT on ia64.
Oh, I forgot about the whole SoEMT fiasco.
Yeah, that might make ia64 act a bit differently here.
But I don't think anybody cares any more, so I don't think that merits
making this a per-architecture choice.
The s390 people hated cpu_relax() here, but for them it was really
because it was bad *everywhere*, and they just made it a no-op (see
commit 22b6430d3665 "locking/core, s390: Make cpu_relax() a barrier
again"). There had been a (failed) attempt at "cpu_relax_lowlatency()"
for the s390 issues.
Linus
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