linux-kernel - Re: [PATCH v3] arm64: mm: Fix NOMAP page initialization

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Date:   Mon, 9 Jan 2017 12:53:20 +0100
From:   Robert Richter <robert.richter@...ium.com>
To:     Ard Biesheuvel <ard.biesheuvel@...aro.org>
CC:     Hanjun Guo <hanjun.guo@...aro.org>,
        Russell King <linux@...linux.org.uk>,
        Catalin Marinas <catalin.marinas@....com>,
        Will Deacon <will.deacon@....com>,
        David Daney <david.daney@...ium.com>,
        Mark Rutland <mark.rutland@....com>,
        James Morse <james.morse@....com>,
        Yisheng Xie <xieyisheng1@...wei.com>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [PATCH v3] arm64: mm: Fix NOMAP page initialization

On 06.01.17 08:37:25, Ard Biesheuvel wrote:
> Any comments on the performance impact (including boot time) ?

I did a kernel compile test and kernel mode time increases by about
2.2%. Though this is already significant, we need a more suitable mem
benchmark here for further testing.

For boot time I dont see significant changes.

-Robert


Boot times:

pfn_valid_within():
[   25.929134]
[   25.548830]
[   25.503225]

early_pfn_valid() v3:
[   25.773814]
[   25.548428]
[   25.765290]


Kernel compile times (3 runs each):

pfn_valid_within():

real    6m4.088s
user    372m57.607s
sys     16m55.158s

real    6m1.532s
user    372m48.453s
sys     16m50.370s

real    6m4.061s
user    373m18.753s
sys     16m57.027s


early_pfn_valid() v3:

real    6m3.261s
user    373m15.816s
sys     16m30.019s

real    6m2.980s
user    373m9.019s
sys     16m32.992s

real    6m2.574s
user    372m45.146s
sys     16m33.218s