linux-kernel - Re: [dm-devel] [PATCH] sched: make struct task

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Message-ID: <20190903065155.GA28322@infradead.org>
Date:   Mon, 2 Sep 2019 23:51:55 -0700
From:   Christoph Hellwig <hch@...radead.org>
To:     Alexey Dobriyan <adobriyan@...il.com>
Cc:     mingo@...hat.com, peterz@...radead.org, aarcange@...hat.com,
        linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
        rcu@...r.kernel.org, dm-devel@...hat.com, axboe@...nel.dk
Subject: Re: [dm-devel] [PATCH] sched: make struct task_struct::state 32-bit

On Tue, Sep 03, 2019 at 12:05:58AM +0300, Alexey Dobriyan wrote:
> 32-bit accesses are shorter than 64-bit accesses on x86_64.
> Nothing uses 64-bitness of ->state.
> 
> Space savings are ~2KB on F30 kernel config.

I guess we'd save even more when moving from a volatile to
WRITE_ONCE/READ_ONCE..