On 05/03/2012 08:15 AM, Takuya Yoshikawa wrote: > 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? > Takuya, i am sorry, please forgive my rudeness! Since my English is so poor that it is easy for me to misunderstand the mail. :( > 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. > Actually, the improvement is larger than v2/v3 if ept is enabled, but it is lower for ept disabled. This is because the fask-fask (rmap.WRITABLE bit) is dropped for better review. > > 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. > Of course, any measurement is appreciative! > >>> 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. Sorry again. -- 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
