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Date: Tue, 05 May 2015 12:15:00 -0700
From: Dave Hansen <dave.hansen@linux.intel.com>
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To: Ingo Molnar <mingo@kernel.org>, linux-kernel@vger.kernel.org
CC: Andy Lutomirski <luto@amacapital.net>, Borislav Petkov <bp@alien8.de>,
        Fenghua Yu <fenghua.yu@intel.com>, "H. Peter Anvin" <hpa@zytor.com>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Oleg Nesterov <oleg@redhat.com>, Thomas Gleixner <tglx@linutronix.de>
Subject: Re: [PATCH 207/208] x86/fpu: Add FPU performance measurement subsystem
References: <1430848712-28064-1-git-send-email-mingo@kernel.org> <1430848712-28064-47-git-send-email-mingo@kernel.org>
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On 05/05/2015 10:58 AM, Ingo Molnar wrote:
>   x86/fpu: Cost of: XSAVE                       insn          :   104 cycles
>   x86/fpu: Cost of: XRSTOR                      insn          :    80 cycles

Isn't there going to be pretty huge variability here depending on how
much state you are xsave/xrstor'ing and if the init/modified
optimizations are in play?