From mboxrd@z Thu Jan  1 00:00:00 1970
From: Heiko Carstens <heiko.carstens@de.ibm.com>
Subject: [patch 0/4] Allow inlined spinlocks again V2
Date: Tue, 11 Aug 2009 14:47:56 +0200
Message-ID: <20090811124756.873490673@de.ibm.com>
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To: Andrew Morton <akpm@linux-foundation.org>, Linus Torvalds <torvalds@linux-foundation.org>, Peter Zijlstra <a.p.zijlstra@chello.nl>, Ingo Molnar <mingo@elte.hu>
Cc: linux-arch@vger.kernel.org, Martin Schwidefsky <schwidefsky@de.ibm.com>, Heiko Carstens <heiko.carstens@de.ibm.com>

This patch set allows to have inlined spinlocks again.

V2: rewritten from scratch - now with readable code

The rationale behind this is that function calls on at least s390 are
expensive.

If one considers that server kernels are usually compiled with
!CONFIG_PREEMPT a simple spin_lock is just a compare and swap loop.
The extra overhead for a function call is significant.
With inlined spinlocks overall cpu usage gets reduced by 1%-5% on s390.
These numbers were taken with some network benchmarks. However I expect
any workload that calls frequently into the kernel and which grabs a few
locks to perform better.

The implementation is straight forward: move the function bodies of the
locking functions to static inline functions and place them in a header
file.
Dependent on CONFIG_SPINLOCK_INLINE generate out-of-line or inlined
locking functions.

The patches should be self explaining.