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

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Date:   Mon, 24 Aug 2020 15:38:53 +0000
From:   "Luck, Tony" <tony.luck@...el.com>
To:     "Tang, Feng" <feng.tang@...el.com>, Borislav Petkov <bp@...e.de>
CC:     "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

> 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.

-Tony