From: Paolo Bonzini <pbonzini@redhat.com>
To: riel@redhat.com, linux-kernel@vger.kernel.org
Cc: dave.hansen@linux.intel.com, x86@kernel.org, tglx@linutronix.de,
mingo@redhat.com, luto@kernel.org, pa@zytor.com, bp@suse.de
Subject: Re: [PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode
Date: Wed, 5 Oct 2016 09:14:21 +0200 [thread overview]
Message-ID: <f3a95fc0-2a98-5627-7cea-8847ee6496e7@redhat.com> (raw)
In-Reply-To: <1475627678-20788-3-git-send-email-riel@redhat.com>
On 05/10/2016 02:34, riel@redhat.com wrote:
> From: Andy Lutomirski <luto@kernel.org>
>
> Since commit 58122bf1d856 ("x86/fpu: Default eagerfpu=on on all
> CPUs") in Linux 4.6, eager FPU mode has been the default on all x86
> systems, and no one has reported any regressions.
>
> This patch removes the ability to enable lazy mode: use_eager_fpu()
> becomes "return true" and all of the FPU mode selection machinery is
> removed.
I haven't quite followed up on my promise to benchmark lazy vs. eager
FPU, but I probably should do that now...
I see two possible issues with this. First, AMD as far as I know does
not have XSAVEOPT. Second, when using virtualization, depending on how
you configure your cluster it's enough to have one pre-SandyBridge Intel
machine to force no XSAVE on all machines.
Thanks,
Paolo
next prev parent reply other threads:[~2016-10-05 7:14 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-05 0:34 [PATCH 0/9] x86/fpu: remove lazy FPU mode & various FPU cleanups riel
2016-10-05 0:34 ` [PATCH 1/9] x86/crypto: Remove X86_FEATURE_EAGER_FPU ifdef from the crc32c code riel
2016-10-05 0:40 ` Rik van Riel
2016-10-07 9:43 ` [tip:x86/fpu] x86/crypto, x86/fpu: Remove X86_FEATURE_EAGER_FPU #ifdef " tip-bot for Andy Lutomirski
2016-10-05 0:34 ` [PATCH 2/9] x86/fpu: Hard-disable lazy fpu mode riel
2016-10-05 7:14 ` Paolo Bonzini [this message]
2016-10-05 13:57 ` Rik van Riel
2016-10-05 14:03 ` Paolo Bonzini
2016-10-05 15:59 ` Andy Lutomirski
2016-10-05 16:09 ` Paolo Bonzini
2016-10-07 9:43 ` [tip:x86/fpu] x86/fpu: Hard-disable lazy FPU mode tip-bot for Andy Lutomirski
2016-10-05 0:34 ` [PATCH 3/9] x86/fpu: Remove the XFEATURE_MASK_EAGER/LAZY distinction riel
2016-10-07 9:44 ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2016-10-05 0:34 ` [PATCH 4/9] x86/fpu: Remove use_eager_fpu() riel
2016-10-07 9:44 ` [tip:x86/fpu] " tip-bot for Andy Lutomirski
2016-10-05 0:34 ` [PATCH 5/9] x86/fpu: remove fpu.counter riel
2016-10-05 2:07 ` Andy Lutomirski
2016-10-07 9:45 ` [tip:x86/fpu] x86/fpu: Remove struct fpu::counter tip-bot for Rik van Riel
2016-10-05 0:34 ` [PATCH 6/9] x86/fpu,kvm: remove kvm vcpu->fpu_counter riel
2016-10-07 9:45 ` [tip:x86/fpu] x86/fpu, kvm: Remove KVM vcpu->fpu_counter tip-bot for Rik van Riel
2016-10-05 0:34 ` [PATCH 7/9] x86/fpu: rename lazy restore functions to "register state valid" riel
2016-10-05 2:09 ` Andy Lutomirski
2016-10-07 9:46 ` [tip:x86/fpu] x86/fpu: Rename " tip-bot for Rik van Riel
2016-10-05 0:34 ` [PATCH 8/9] x86/fpu: remove __fpregs_(de)activate riel
2016-10-05 2:10 ` Andy Lutomirski
2016-10-07 9:46 ` [tip:x86/fpu] x86/fpu: Remove __fpregs_(de)activate() tip-bot for Rik van Riel
2016-10-05 0:34 ` [PATCH 9/9] x86/fpu: split old & new fpu code paths riel
2016-10-07 9:47 ` [tip:x86/fpu] x86/fpu: Split old & new FPU " tip-bot for Rik van Riel
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