linux-kernel - Re: [LKP] [x86, retpolines] ce02ef06fc: will-it-scale.per_thread

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Date:   Mon, 29 Apr 2019 14:53:20 +0200
From:   Greg KH <greg@...ah.com>
To:     Daniel Borkmann <daniel@...earbox.net>
Cc:     kernel test robot <rong.a.chen@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Björn Töpel <bjorn.topel@...el.com>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        "David S. Miller" <davem@...emloft.net>,
        Magnus Karlsson <magnus.karlsson@...el.com>,
        Alexei Starovoitov <ast@...nel.org>,
        Peter Zijlstra <peterz@...radead.org>,
        David Woodhouse <dwmw2@...radead.org>,
        Andy Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        LKML <linux-kernel@...r.kernel.org>, lkp@...org
Subject: Re: [LKP] [x86, retpolines] ce02ef06fc: will-it-scale.per_thread_ops
 3.1% improvement

On Thu, Mar 14, 2019 at 09:39:35AM +0100, Daniel Borkmann wrote:
> On 03/13/2019 06:27 AM, kernel test robot wrote:
> > Greeting,
> > 
> > FYI, we noticed a 3.1% improvement of will-it-scale.per_thread_ops due to commit:
> > 
> > 
> > commit: ce02ef06fcf7a399a6276adb83f37373d10cbbe1 ("x86, retpolines: Raise limit for generating indirect calls from switch-case")
> > https://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git master
> > 
> > in testcase: will-it-scale
> > on test machine: 88 threads Intel(R) Xeon(R) CPU E5-2699 v4 @ 2.20GHz with 64G memory
> > with following parameters:
> > 
> > 	nr_task: 100%
> > 	mode: thread
> > 	test: futex3
> > 	cpufreq_governor: performance
> > 	ucode: 0xb00002e
> > 
> > test-description: Will It Scale takes a testcase and runs it from 1 through to n parallel copies to see if the testcase will scale. It builds both a process and threads based test in order to see any differences between the two.
> > test-url: https://github.com/antonblanchard/will-it-scale
> > 
> > In addition to that, the commit also has significant impact on the following tests:
> 
> Any thoughts on whether the above one-liner gcc work-around should be backported
> to stable as well given these gains?

I have now done so, thanks.

greg k-h