Please sign in to comment.
This commit does not belong to any branch on this repository, and may belong to a fork outside of the repository.
x86/fpu: Default eagerfpu=on on all CPUs
We have eager and lazy FPU modes, introduced in: 304bced ("x86, fpu: use non-lazy fpu restore for processors supporting xsave") The result is rather messy. There are two code paths in almost all of the FPU code, and only one of them (the eager case) is tested frequently, since most kernel developers have new enough hardware that we use eagerfpu. It seems that, on any remotely recent hardware, eagerfpu is a win: glibc uses SSE2, so laziness is probably overoptimistic, and, in any case, manipulating TS is far slower that saving and restoring the full state. (Stores to CR0.TS are serializing and are poorly optimized.) To try to shake out any latent issues on old hardware, this changes the default to eager on all CPUs. If no performance or functionality problems show up, a subsequent patch could remove lazy mode entirely. Signed-off-by: Andy Lutomirski <email@example.com> Cc: Andy Lutomirski <firstname.lastname@example.org> Cc: Borislav Petkov <email@example.com> Cc: Dave Hansen <firstname.lastname@example.org> Cc: Fenghua Yu <email@example.com> Cc: H. Peter Anvin <firstname.lastname@example.org> Cc: Linus Torvalds <email@example.com> Cc: Oleg Nesterov <firstname.lastname@example.org> Cc: Peter Zijlstra <email@example.com> Cc: Quentin Casasnovas <firstname.lastname@example.org> Cc: Rik van Riel <email@example.com> Cc: Sai Praneeth Prakhya <firstname.lastname@example.org> Cc: Thomas Gleixner <email@example.com> Cc: yu-cheng yu <firstname.lastname@example.org> Link: http://email@example.com Signed-off-by: Ingo Molnar <firstname.lastname@example.org>
- Loading branch information