On Fri, Dec 13, 2013 at 10:11:05AM +0800, Alex Shi wrote: > BTW, > A bewitching idea is till attracting me. > https://lkml.org/lkml/2012/5/23/148 > Even it was sentenced to death by HPA. > https://lkml.org/lkml/2012/5/24/143 > > That is that just flush one of thread TLB is enough for SMT/HT, seems > TLB is still shared in core on Intel CPU. This benefit is unconditional, > and if my memory right, Kbuild testing can improve about 1~2% in average > level. > > So could you like to accept some ugly quirks to do this lazy TLB flush > on known working CPU? > Forgive me if it's stupid. I think there's a further problem with that patch -- aside of it being right from a hardware point of view. We currently rely on the tlb flush IPI to synchronize with lockless page table walkers like gup_fast(). By not sending an IPI to all CPUs you can get into trouble and crash the kernel. We absolutely must keep sending the IPI to all relevant CPUs, we can choose not to actually do the flush on some CPUs, but we must keep sending the IPI. -- 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/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>