linux-kernel - Re: [PATCH 0/5] kernel/cpu.c: eliminate some indirection

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Date:	Thu, 11 Jun 2015 11:31:41 +0200
From:	Rasmus Villemoes <linux@...musvillemoes.dk>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	"Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/5] kernel/cpu.c: eliminate some indirection

On Thu, May 07 2015, Rasmus Villemoes <linux@...musvillemoes.dk> wrote:

> The four cpumasks cpu_{possible,online,present,active}_bits are
> exposed readonly via the corresponding const variables
> cpu_xyz_mask. But they are also accessible for arbitrary writing via
> the exposed functions set_cpu_xyz. There's quite a bit of code
> throughout the kernel which iterates over or otherwise accesses these
> bitmaps, and having the access go via the cpu_xyz_mask variables is
> simply a useless indirection.
>
> The first four patches eliminate the cpu_xyz_mask variables by simply
> exposing the actual bitmaps, after renaming them to discourage direct
> access - that still happens through cpu_xyz_mask, which are now simply
> macros with the same type and value as they used to have.
>
> After that, there's no longer any reason to have the setter functions
> be out-of-line: The boolean parameter is almost always a literal true
> or false, so by making them static inlines they will usually compile
> to one or two instructions.
>
> Altogether, bloat-o-meter reports a saving of ~2600 bytes.

ping...

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