linux-kernel - Re: [PATCH] checkpatch: Add a --strict test for structs with bool member definitions

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Message-ID: <20180412081323.GV4082@hirez.programming.kicks-ass.net>
Date:   Thu, 12 Apr 2018 10:13:23 +0200
From:   Peter Zijlstra <peterz@...radead.org>
To:     Joe Perches <joe@...ches.com>
Cc:     Julia Lawall <julia.lawall@...6.fr>,
        Andrew Morton <akpm@...ux-foundation.org>,
        "Rafael J. Wysocki" <rafael@...nel.org>,
        Andy Whitcroft <apw@...onical.com>, yuankuiz@...eaurora.org,
        Linux PM <linux-pm@...r.kernel.org>,
        "Rafael J. Wysocki" <rjw@...ysocki.net>,
        Frederic Weisbecker <fweisbec@...il.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        paulmck@...ux.vnet.ibm.com, Ingo Molnar <mingo@...nel.org>,
        Len Brown <len.brown@...el.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] checkpatch: Add a --strict test for structs with bool
 member definitions

On Wed, Apr 11, 2018 at 11:42:20PM -0700, Joe Perches wrote:
> I personally do not find a significant issue with
> uncontrolled sizes of bool in kernel structs as
> all of the kernel structs are transitory and not
> written out to storage.

People that care about cache locality, false sharing and other such
things really care about structure layout.

Growing a structure into another cacheline can be a significant
performance hit -- cache misses hurt.