On 2011.11.22 at 09:27 +0100, Eric Dumazet wrote: > Le mardi 22 novembre 2011 à 08:48 +0100, Eric Dumazet a écrit : > > > For x86, I wonder if our !X86_FEATURE_CX16 support is correct on SMP > > machines. > > > > > By the way, I wonder why we still emit this_cpu_cmpxchg16b_emu() code > and calls when compiling a kernel for a cpu implementing cmpxchg16b > > (CONFIG_MCORE2=y) Yeah, it's strange (CONFIG_MK8): ffffffff811058b0 <__kmalloc>: ... ffffffff8110594f: 48 8d 4a 04 lea 0x4(%rdx),%rcx ffffffff81105953: 49 8b 1c 04 mov (%r12,%rax,1),%rbx ffffffff81105957: 4c 89 e0 mov %r12,%rax ffffffff8110595a: e8 11 70 10 00 callq ffffffff8120c970 <this_cpu_cmpxchg16b_emu> ffffffff8110595f: 66 66 90 data32 xchg %ax,%ax ffffffff81105962: 84 c0 test %al,%al ffffffff81105964: 74 c6 je ffffffff8110592c <__kmalloc+0x7c> ... There is a comment in arch/x86/include/asm/percpu.h: * Pretty complex macro to generate cmpxchg16 instruction. The instruction * is not supported on early AMD64 processors so we must be able to emulate * it in software. The address used in the cmpxchg16 instruction must be * aligned to a 16 byte boundary. -- Markus -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>