Re: [dm-devel] [PATCH] sched: make struct task_struct::state 32-bit

[Peter Zijlstra]

On Mon, Sep 02, 2019 at 11:51:55PM -0700, Christoph Hellwig wrote:
> 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..

I doubt it; pretty much all accesses really should be using that.

Not saying we shouldn't maybe do that; but that's going to be massive
churn.