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
Date: Fri, 10 Feb 2017 12:53:52 +0100 (CET) [thread overview]
Message-ID: <alpine.DEB.2.20.1702101252450.4036@nanos> (raw)
In-Reply-To: <1486060589-31572-1-git-send-email-longman@redhat.com>
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?
prev parent reply other threads:[~2017-02-10 16:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-02-02 18:36 Waiman Long
2017-02-10 11:53 ` Thomas Gleixner [this message]
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