linux-kernel - Re: [PATCH] lib/int_sqrt.c: Optimize square root function

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date:   Fri, 21 Jul 2017 15:33:00 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Linus Torvalds <torvalds@...ux-foundation.org>,
        Anshul Garg <aksgarg1989@...il.com>,
        Davidlohr Bueso <dave@...olabs.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        "anshul.g@...sung.com" <anshul.g@...sung.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>,
        Will Deacon <will.deacon@....com>
Subject: Re: [PATCH] lib/int_sqrt.c: Optimize square root function

On Fri, Jul 21, 2017 at 03:26:21PM +0200, Peter Zijlstra wrote:
> 
> EVENT=0 -DNEW=1 -DFLS=1
> event: 19.626050 +- 0.038995
> EVENT=0 -DNEW=1 -DFLS=1 -DWIPE_BTB=1
> event: 109.610670 +- 0.425667
> 
> EVENT=0 -DNEW=1 -DFLS=1 -DANSHUL=1
> event: 21.445680 +- 0.043782
> EVENT=0 -DNEW=1 -DFLS=1 -DANSHUL=1 -DWIPE_BTB=1
> event: 83.590420 +- 0.142126
> 

> Let me dig out another GCC version current:
> 
>   gcc (Debian 6.3.0-18) 6.3.0 20170516

gcc-7 (Debian 7.1.0-9) 7.1.0

EVENT=0 -DNEW=1 -DFLS=1
event: 24.179400 +- 0.031344
EVENT=0 -DNEW=1 -DFLS=1 -DWIPE_BTB=1
event: 137.892390 +- 0.307314

EVENT=0 -DNEW=1 -DFLS=1 -DANSHUL=1
event: 22.740300 +- 0.051317
EVENT=0 -DNEW=1 -DFLS=1 -DANSHUL=1 -DWIPE_BTB=1
event: 136.980640 +- 0.223410


GCC regressed it seems... *sigh*