Messages in this thread | | | Subject | Re: [PATCH 0/7] KVM: MMU: fast write protect | From | Xiao Guangrong <> | Date | Thu, 4 May 2017 11:36:55 +0800 |
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On 05/03/2017 10:57 PM, Paolo Bonzini wrote: > > > On 03/05/2017 16:50, Xiao Guangrong wrote: >> Furthermore, userspace has no knowledge about if PML is enable (it >> can be required from sysfs, but it is a good way in QEMU), so it is >> difficult for the usespace to know when to use write-protect-all. >> Maybe we can make KVM_CAP_X86_WRITE_PROTECT_ALL_MEM return false if >> PML is enabled? > > Yes, that's a good idea. Though it's a pity that, with PML, setting the > dirty bit will still do the massive walk of the rmap. At least with > reset_dirty_pages it's done a little bit at a time. > >>> Also, I wonder how the alternative write protection mechanism would >>> affect performance of the dirty page ring buffer patches. You would do >>> the write protection of all memory at the end of >>> kvm_vm_ioctl_reset_dirty_pages. You wouldn't even need a separate >>> ioctl, which is nice. On the other hand, checkpoints would be more >>> frequent and most pages would be write-protected, so it would be more >>> expensive to rebuild the shadow page tables... >> >> Yup, write-protect-all can improve reset_dirty_pages indeed, i will >> apply your idea after reset_dirty_pages is merged. >> >> However, we still prefer to have a separate ioctl for write-protect-all >> which cooperates with KVM_GET_DIRTY_LOG to improve live migration that >> should not always depend on checkpoint. > > Ok, I plan to merge the dirty ring pages early in 4.13 development.
Great.
As there is no conflict between these two patchsets except dirty ring pages takes benefit from write-protect-all, i think they can be developed and iterated independently, right?
Or you prefer to merge dirty ring pages first then review the new version of this patchset later?
Thanks!
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