linux-kernel - Re: [LKP] Re: [x86/mce] 1de08dccd3: will-it-scale.per_process

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Message-ID: <20200824154818.GB56944@shbuild999.sh.intel.com>
Date:   Mon, 24 Aug 2020 23:48:18 +0800
From:   Feng Tang <feng.tang@...el.com>
To:     "Luck, Tony" <tony.luck@...el.com>
Cc:     Borislav Petkov <bp@...e.de>,
        "Chen, Rong A" <rong.a.chen@...el.com>,
        LKML <linux-kernel@...r.kernel.org>,
        "lkp@...ts.01.org" <lkp@...ts.01.org>,
        Mel Gorman <mgorman@...e.com>
Subject: Re: [LKP] Re: [x86/mce] 1de08dccd3: will-it-scale.per_process_ops
 -14.1% regression

On Mon, Aug 24, 2020 at 11:38:53PM +0800, Luck, Tony wrote:
> > Yes, that's what we suspected. And I just did another try to force the
> > percpu mce structure aligned. And the regression seems to be gone (reduced
> > from 14.1% to 2%), which further proved it.
> 
> I wonder whether it would be useful for bisection of performance issues
> for you to change the global definition of DEFINE_PER_CPU() to make
> all per CPU definitions aligned. Just like you switch compiler flags to make
> all functions aligned.

Thanks for the hint! This will definitely help tracking strange performance
changes like this, as a general debug mthod.

Thanks,
Feng

> 
> -Tony