linux-kernel - [patch 0/3] x86/process: Optimize __switch_to

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Message-Id: <20161215162648.061449202@linutronix.de>
Date:   Thu, 15 Dec 2016 16:44:01 -0000
From:   Thomas Gleixner <tglx@...utronix.de>
To:     LKML <linux-kernel@...r.kernel.org>
Cc:     x86@...nel.org, Peter Zijlstra <peterz@...radead.org>,
        Kyle Huey <khuey@...ehuey.com>,
        Andy Lutomirski <luto@...nel.org>
Subject: [patch 0/3] x86/process: Optimize __switch_to_extra()

GCC generates lousy code in __switch_to_extra(). Aside of that some of the
operations there are implemented suboptimal.

This series, inspired by a patch from Kyle, helps the compiler to be less
stupid by explicitely giving the hints to optimize and replaces the open
coded bit toggle mechanisms with proper helper functions.

The resulting change in text size:

	 64bit	    32bit
Before:	  3726	     9388
After:	  3646	     9324
Delta:	    80	      152	    

The number of conditional jumps is also reduced:

	 64bit	    32bit
Before:	     8	       13
After:	     5	       10

Thanks,

	tglx

---
 include/asm/processor.h |   12 ++++++++
 include/asm/tlbflush.h  |   10 ++++++
 kernel/process.c        |   70 +++++++++++++++++++-----------------------------
 3 files changed, 51 insertions(+), 41 deletions(-)