From mboxrd@z Thu Jan  1 00:00:00 1970
From: Borislav Petkov <bp@alien8.de>
Subject: Re: [PATCH v6] x86: load FPU registers on return to userland
Date: Wed, 30 Jan 2019 12:35:55 +0100
Message-ID: <20190130113555.GC18383@zn.tnic>
References: <20190109114744.10936-1-bigeasy@linutronix.de>
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Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
        Andy Lutomirski <luto@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Radim =?utf-8?B?S3LEjW3DocWZ?= <rkrcmar@redhat.com>,
        kvm@vger.kernel.org, "Jason A. Donenfeld" <Jason@zx2c4.com>,
        Rik van Riel <riel@surriel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>
To: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
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On Wed, Jan 09, 2019 at 12:47:22PM +0100, Sebastian Andrzej Siewior wrote:
> This is a refurbished series originally started by by Rik van Riel. The
> goal is load the FPU registers on return to userland and not on every
> context switch. By this optimisation we can:
> - avoid loading the registers if the task stays in kernel and does
>   not return to userland
> - make kernel_fpu_begin() cheaper: it only saves the registers on the
>   first invocation. The second invocation does not need save them again.

Btw, do we have any benchmark data showing the improvement this brings?

-- 
Regards/Gruss,
    Boris.

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