From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S1753293AbdBJQE3 (ORCPT <rfc822;w@1wt.eu>);
        Fri, 10 Feb 2017 11:04:29 -0500
Received: from Galois.linutronix.de ([146.0.238.70]:33229 "EHLO
        Galois.linutronix.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S1753113AbdBJQEN (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Fri, 10 Feb 2017 11:04:13 -0500
Date: Fri, 10 Feb 2017 12:53:52 +0100 (CET)
From: Thomas Gleixner <tglx@linutronix.de>
To: Waiman Long <longman@redhat.com>
cc: Ingo Molnar <mingo@redhat.com>, "H. Peter Anvin" <hpa@zytor.com>,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH] x86, locking: Inline *_unlock_bh & *_unlock_irqrestore
In-Reply-To: <1486060589-31572-1-git-send-email-longman@redhat.com>
Message-ID: <alpine.DEB.2.20.1702101252450.4036@nanos>
References: <1486060589-31572-1-git-send-email-longman@redhat.com>
User-Agent: Alpine 2.20 (DEB 67 2015-01-07)
MIME-Version: 1.0
Content-Type: text/plain; charset=US-ASCII
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Thu, 2 Feb 2017, Waiman Long wrote:

> For spinlock and read-write locks, both *_unlock() and *_unlock_irq()
> functions are inlined if !PREEMPT. Whereas the *_unlock_bh() and
> *unlock_irqrestore() are not inlined as that will increase the size
> of the kernel binary.
> 
> Given the fact that the PV qspinlock unlock call is a callee-saved
> function pointer, the unlock function is essentially a leaf function
> if !PREEMPT is true under all circumstances. Inlining it will enable
> the compiler to do much better optimization around the the unlock
> call sites. Similarly for the read-write locks.
> 
> To unleash this additional performance, all these unlock functions
> are now inlined for x86-64 kernel where kernel size is usually less
> of a concern. For 32-bit kernel, it is assumed that the focus will
> be a bit more on kernel size optimization and so those functions are
> not inlined.
> 
> With 4.9.6 kernel source and gcc 4.8.5-11 compiler, the text size
> of the base vmlinux binary increased from 8527918 bytes to 8462235
> bytes. That was an increase of 0.78%.

Increased from 8527918 bytes to 8462235?