On Mon, Apr 18, 2016 at 02:36:31PM +0000, Li, Liang Z wrote: > > On Mon, Apr 18, 2016 at 11:08:31AM +0000, Li, Liang Z wrote: > > > Hi Dave, > > > > > > I am now working on how to benefit post-copy by skipping the free > > > pages, and I remember you have said we should let the destination know > > > the info of free pages so as to avoid request the free pages from the > > source. > > > > > > We have two solutions: > > > > > > a. send the migration dirty page bitmap to destination before post > > > copy start, so the destination can decide whether to request the pages > > > or place zero pages by checking the migration dirty page bitmap. The > > > advantage is that we can avoid sending the free pages. the > > > disadvantage is that we have to send extra data to destination. > > > > > > b. Check the page request on the source side, if it's not a dirty > > > page, send a zero page header to the destination. > > > > > > What's your opinion about them? > > > > > > Liang > > > > > > > Both are ad-hoc solutions imho. > > > > c. put the bitmap in a ramblock, check it on destination before > > requesting pages. > > > > This way it's migrated on-demand. > > > Hi MST, > > I think you mean putting the free page bitmap in a ramblock. Right? > If some of the free pages become dirty after updating the free page bitmap, > and these pages are discarded by destination, how can we distinguish these > discarded pages with the free pages? > > Could you elaborate how it works? > > Thanks! > Liang
Maybe I'm confused - IIUC it's postcopy so VM is running on destination, if page is dirty it was modified there so we don't need to get it from source. But really I agree with David here - at step 1 just ignore postcopy, don't special-case it, even if it becomes slower with your patch. Think about it later. > > > > -- > > MST > > -- > > To unsubscribe from this list: send the line "unsubscribe kvm" in the body > > of > > a message to majord...@vger.kernel.org More majordomo info at > > http://vger.kernel.org/majordomo-info.html
