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Date: Thu, 23 Feb 2012 21:42:39 -0500 From: Jason Baron <jbaron@...hat.com> To: Ingo Molnar <mingo@...e.hu> Cc: Linus Torvalds <torvalds@...ux-foundation.org>, Paul Mackerras <paulus@...ba.org>, "H. Peter Anvin" <hpa@...or.com>, Steven Rostedt <rostedt@...dmis.org>, a.p.zijlstra@...llo.nl, mathieu.desnoyers@...icios.com, davem@...emloft.net, ddaney.cavm@...il.com, akpm@...ux-foundation.org, linux-kernel@...r.kernel.org Subject: Re: [PATCH 00/10] jump label: introduce very_[un]likely + cleanups + docs On Thu, Feb 23, 2012 at 11:33:48PM +0100, Ingo Molnar wrote: > > Before: > > ffffffff810441f0 <sys_getppid>: > ffffffff810441f0: 8b 05 8a 52 d8 00 mov 0xd8528a(%rip),%eax # ffffffff81dc9480 <key> > ffffffff810441f6: 55 push %rbp > ffffffff810441f7: 48 89 e5 mov %rsp,%rbp > ffffffff810441fa: 85 c0 test %eax,%eax > ffffffff810441fc: 75 27 jne ffffffff81044225 <sys_getppid+0x35> > ffffffff810441fe: 65 48 8b 04 25 c0 b6 mov %gs:0xb6c0,%rax > ffffffff81044205: 00 00 > ffffffff81044207: 48 8b 80 80 02 00 00 mov 0x280(%rax),%rax > ffffffff8104420e: 48 8b 80 b0 02 00 00 mov 0x2b0(%rax),%rax > ffffffff81044215: 48 8b b8 e8 02 00 00 mov 0x2e8(%rax),%rdi > ffffffff8104421c: e8 2f da 00 00 callq ffffffff81051c50 <pid_vnr> > ffffffff81044221: 5d pop %rbp > ffffffff81044222: 48 98 cltq > ffffffff81044224: c3 retq > ffffffff81044225: 48 c7 c7 13 53 98 81 mov $0xffffffff81985313,%rdi > ffffffff8104422c: 31 c0 xor %eax,%eax > ffffffff8104422e: e8 60 0f 6d 00 callq ffffffff81715193 <printk> > ffffffff81044233: eb c9 jmp ffffffff810441fe <sys_getppid+0xe> > ffffffff81044235: 66 66 2e 0f 1f 84 00 data32 nopw %cs:0x0(%rax,%rax,1) > ffffffff8104423c: 00 00 00 00 > > After: > > ffffffff81044290 <sys_getppid>: > ffffffff81044290: 55 push %rbp > ffffffff81044291: 48 89 e5 mov %rsp,%rbp > ffffffff81044294: e9 00 00 00 00 jmpq ffffffff81044299 <sys_getppid+0x9> > ffffffff81044299: 65 48 8b 04 25 c0 b6 mov %gs:0xb6c0,%rax > ffffffff810442a0: 00 00 > ffffffff810442a2: 48 8b 80 80 02 00 00 mov 0x280(%rax),%rax > ffffffff810442a9: 48 8b 80 b0 02 00 00 mov 0x2b0(%rax),%rax > ffffffff810442b0: 48 8b b8 e8 02 00 00 mov 0x2e8(%rax),%rdi > ffffffff810442b7: e8 f4 d9 00 00 callq ffffffff81051cb0 <pid_vnr> > ffffffff810442bc: 5d pop %rbp > ffffffff810442bd: 48 98 cltq > ffffffff810442bf: c3 retq > ffffffff810442c0: 48 c7 c7 e3 54 98 81 mov $0xffffffff819854e3,%rdi > ffffffff810442c7: 31 c0 xor %eax,%eax > ffffffff810442c9: e8 71 13 6d 00 callq ffffffff8171563f <printk> > ffffffff810442ce: eb c9 jmp ffffffff81044299 <sys_getppid+0x9> > > The prior slowpath test: > > ffffffff810441fa: 85 c0 test %eax,%eax > ffffffff810441fc: 75 27 jne ffffffff81044225 <sys_getppid+0x35> > > became even faster and turned into a single NOP, making the > fastpath even faster. > and the: mov 0xd8528a(%rip),%eax # ffffffff81dc9480 <key> is no longer present. Thanks, -Jason -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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