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authorEric Dumazet <dada1@cosmosbay.com>2007-05-08 00:25:32 -0700
committerLinus Torvalds <torvalds@woody.linux-foundation.org>2007-05-08 11:15:01 -0700
commit753e9c5cd9b123156152c66c816f751954b15e53 (patch)
treefc70e4358be312e11ce0c258ead7b996dbd7d59e /mm/filemap.h
parent2e17c5508fa015f2c7690e29041f437e9308c64f (diff)
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Optimize timespec_trunc()
The first thing done by timespec_trunc() is : if (gran <= jiffies_to_usecs(1) * 1000) This should really be a test against a constant known at compile time. Alas, it isnt. jiffies_to_usec() was unilined so C compiler emits a function call and a multiply to compute : a CONSTANT. mov $0x1,%edi mov %rbx,0xffffffffffffffe8(%rbp) mov %r12,0xfffffffffffffff0(%rbp) mov %edx,%ebx mov %rsi,0xffffffffffffffc8(%rbp) mov %rsi,%r12 callq ffffffff80232010 <jiffies_to_usecs> imul $0x3e8,%eax,%eax cmp %ebx,%eax This patch reorders kernel/time.c a bit so that jiffies_to_usecs() is defined before timespec_trunc() so that compiler now generates : cmp $0x3d0900,%edx (HZ=250 on my machine) This gives a better code (timespec_trunc() becoming a leaf function), and shorter kernel size as well. Signed-off-by: Eric Dumazet <dada1@cosmosbay.com> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Ingo Molnar <mingo@elte.hu> Cc: john stultz <johnstul@us.ibm.com> Cc: Roman Zippel <zippel@linux-m68k.org> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'mm/filemap.h')
0 files changed, 0 insertions, 0 deletions