From: Dave Hansen <dave.hansen@linux.intel.com>
To: riel@redhat.com, linux-kernel@vger.kernel.org
Cc: x86@kernel.org, tglx@linutronix.de, pbonzini@redhat.com,
mingo@redhat.com, luto@kernel.org, hpa@zytor.com, bp@suse.de
Subject: Re: [PATCH RFC 4/5] x86,fpu: lazily skip FPU restore when still loaded
Date: Mon, 3 Oct 2016 13:04:57 -0700 [thread overview]
Message-ID: <57F2B9E9.7030806@linux.intel.com> (raw)
In-Reply-To: <1475353895-22175-5-git-send-email-riel@redhat.com>
On 10/01/2016 01:31 PM, riel@redhat.com wrote:
> /*
> + * Check whether an FPU's register set is still loaded in the CPU.
> + */
> +static inline bool fpu_lazy_skip_restore(struct fpu *fpu)
> +{
> + bool still_loaded = (fpu->fpstate_active &&
> + fpu->last_cpu == raw_smp_processor_id() &&
> + __this_cpu_read(fpu_fpregs_owner_ctx) == fpu);
> +
> + fpu->fpregs_active = still_loaded;
> + return still_loaded;
> +}
I wonder if we should call this something more along the lines of
fpregs_activate_fast(), which returns if it managed to do the activation
fast or not. I _think_ that's more along the lines of what it is
actually doing. The fact that it can be lazy is really an
implementation detail.
What are the preempt rules with this thing? This needs to be called in
preempt-disabled contexts, right?
next prev parent reply other threads:[~2016-10-03 20:05 UTC|newest]
Thread overview: 27+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-01 20:31 [PATCH RFC 0/5] x86,fpu: make FPU context switching much lazier riel
2016-10-01 20:31 ` [PATCH RFC 1/5] x86,fpu: split prev/next task fpu state handling riel
2016-10-01 23:26 ` Andy Lutomirski
2016-10-02 0:02 ` Rik van Riel
2016-10-01 20:31 ` [PATCH RFC 2/5] x86,fpu: delay FPU register loading until switch to userspace riel
2016-10-01 23:44 ` Andy Lutomirski
2016-10-02 0:08 ` Rik van Riel
2016-10-03 20:54 ` Andy Lutomirski
2016-10-03 21:21 ` Rik van Riel
2016-10-03 21:36 ` Andy Lutomirski
2016-10-04 1:29 ` Rik van Riel
2016-10-04 2:09 ` Andy Lutomirski
2016-10-04 2:47 ` Rik van Riel
2016-10-04 3:02 ` Andy Lutomirski
2016-10-04 6:35 ` Ingo Molnar
2016-10-04 12:48 ` Rik van Riel
2016-10-04 2:11 ` Rik van Riel
2016-10-04 3:02 ` Andy Lutomirski
2016-10-02 0:42 ` Rik van Riel
2016-10-03 16:23 ` Dave Hansen
2016-10-01 20:31 ` [PATCH RFC 3/5] x86,fpu: add kernel fpu argument to __kernel_fpu_begin riel
2016-10-01 20:31 ` [PATCH RFC 4/5] x86,fpu: lazily skip FPU restore when still loaded riel
2016-10-03 20:04 ` Dave Hansen [this message]
2016-10-03 20:22 ` Rik van Riel
2016-10-03 20:49 ` Dave Hansen
2016-10-03 21:02 ` Rik van Riel
2016-10-01 20:31 ` [PATCH RFC 5/5] x86,fpu: kinda sorta fix up signal path riel
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