On Wed, 02 May 2012 13:39:51 +0800 Xiao Guangrong <xiaoguangrong@xxxxxxxxxxxxxxxxxx> wrote: > > Was the problem really mmu_lock contention? > Takuya, i am so tired to argue the advantage of lockless write-protect > and lockless O(1) dirty-log again and again. You are missing my point. Please do not take my comments as an objection to your whole work: whey do you feel so? I thought that your new fast-page-fault path was fast and optimized the guest during dirty logging. So in this v4, you might get a similar result even before dropping mmu_lock, without 07/10?, if the problem Marcelo explained was not there. Of course there is a problem of mmu_lock contention. What I am suggesting is to split that problem and do measurement separately so that part of your work can be merged soon. Your guest size and workload was small to make get_dirty hold mmu_lock long time. If you want to appeal the real value of lock-less, you need to do another measurment. But this is your work and it's up to you. Although I was thinking to help your measurement, I cannot do that knowing the fact that you would not welcome my help. > > Although I am not certain about what will be really needed in the > > final form, if this kind of maybe-needed-overhead is going to be > > added little by little, I worry about possible regression. > Well, will you suggest Linus to reject all patches and stop > all discussion for the "possible regression" reason? My concern was for Marcelo's examples, not your current implementation. If you can show explicitely what will be needed in the final form, I do not have any concern. Sorry for disturbing. Thanks, Takuya -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
