On 01/12/16 14:10, Michael S. Tsirkin wrote: > mb() typically uses mfence on modern x86, but a micro-benchmark shows that it's > 2 to 3 times slower than lock; addl $0,(%%e/rsp) that we use on older CPUs. > > So let's use the locked variant everywhere - helps keep the code simple as > well. > > While I was at it, I found some inconsistencies in comments in > arch/x86/include/asm/barrier.h > > I hope I'm not splitting this up too much - the reason is I wanted to isolate > the code changes (that people might want to test for performance) from comment > changes approved by Linus, from (so far unreviewed) comment change I came up > with myself. > > Lightly tested on my system. > > Michael S. Tsirkin (3): > x86: drop mfence in favor of lock+addl > x86: drop a comment left over from X86_OOSTORE > x86: tweak the comment about use of wmb for IO > I would like to get feedback from the hardware team about the implications of this change, first. -hpa _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
