Re: [PATCH] x86, locking: Inline *_unlock_bh & *_unlock_irqrestore
From: Thomas Gleixner
Date: Fri Feb 10 2017 - 11:04:38 EST
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?