On Thu, 26 May 2011, H. Peter Anvin wrote: > On 05/26/2011 11:17 AM, Christoph Lameter wrote: > > On Thu, 26 May 2011, H. Peter Anvin wrote: > > > >>> +config CMPXCHG_DOUBLE > >>> + def_bool X86_64 || (X86_32 && !M386) > >>> + > >> > >> CMPXCHG16B is not a baseline feature for the Linux x86-64 build, and > >> CMPXCHG8G is a Pentium, not a 486, feature. > >> > >> Nacked-by: H. Peter Anvin <hpa@xxxxxxxxx> > > > > Hmmm... We may have to call it CONFIG_CMPXCHG_DOUBLE_POSSIBLE then? > > > > Because the slub code tests the flag in the processor and will not use the > > cmpxchg16b from the allocator if its not there. It will then fallback to > > using a bit lock in page struct. > > > > Well, if it is just about being "possible" then it should simply be true > for all of x86. There is no reason to exclude i386 (which is all your > above predicate does, it is exactly equivalent to !M386). Ok. Possible means that the code for cmpxchg16b/8b will be compiled in. Then how do I exclude the code if someone compiles a kernel for a processor that certainly does not support these instructions? -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxxx 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>