This patchset is based on current 'queue' branch on kvm tree. Changlog: V4: 1): drop unmapping invalid rmap out of mmu-lock and use lock-break technique instead. Thanks to Gleb's comments. 2): needn't handle invalid-gen pages specially due to page table always switched by KVM_REQ_MMU_RELOAD. Thanks to Marcelo's comments. V3: completely redesign the algorithm, please see below. V2: - do not reset n_requested_mmu_pages and n_max_mmu_pages - batch free root shadow pages to reduce vcpu notification and mmu-lock contention - remove the first patch that introduce kvm->arch.mmu_cache since we only 'memset zero' on hashtable rather than all mmu cache members in this version - remove unnecessary kvm_reload_remote_mmus after kvm_mmu_zap_all * Issue The current kvm_mmu_zap_all is really slow - it is holding mmu-lock to walk and zap all shadow pages one by one, also it need to zap all guest page's rmap and all shadow page's parent spte list. Particularly, things become worse if guest uses more memory or vcpus. It is not good for scalability. * Idea KVM maintains a global mmu invalid generation-number which is stored in kvm->arch.mmu_valid_gen and every shadow page stores the current global generation-number into sp->mmu_valid_gen when it is created. When KVM need zap all shadow pages sptes, it just simply increase the global generation-number then reload root shadow pages on all vcpus. Vcpu will create a new shadow page table according to current kvm's generation-number. It ensures the old pages are not used any more. The invalid-gen pages (sp->mmu_valid_gen != kvm->arch.mmu_valid_gen) are keeped in mmu-cache until page allocator reclaims page. * Challenges Some page invalidation is requested when memslot is moved or deleted and kvm is being destroy who call zap_all_pages to delete all sp using their rmap and lpage-info, after call zap_all_pages, the rmap and lpage-info will be freed. For the lpage-info, we clear all lpage count when do zap-all-pages, then all invalid shadow pages are not counted in lpage-info, after that lpage-info on the invalid memslot can be safely freed. This is also good for the performance - it allows guest to use hugepage as far as possible. For the rmap, we use lock-break technique to zap all sptes linked on the invalid rmap, it is not very effective but good for the first step. * TODO Unmapping invalid rmap out of mmu-lock with a clear way. Xiao Guangrong (6): KVM: MMU: drop unnecessary kvm_reload_remote_mmus KVM: x86: introduce memslot_set_lpage_disallowed KVM: MMU: introduce kvm_clear_all_lpage_info KVM: MMU: fast invalid all shadow pages KVM: x86: use the fast way to invalid all pages KVM: MMU: make kvm_mmu_zap_all preemptable arch/x86/include/asm/kvm_host.h | 2 + arch/x86/kvm/mmu.c | 88 ++++++++++++++++++++++++++++++++++++++- arch/x86/kvm/mmu.h | 2 + arch/x86/kvm/x86.c | 87 ++++++++++++++++++++++++++++----------- arch/x86/kvm/x86.h | 2 + 5 files changed, 155 insertions(+), 26 deletions(-) -- 1.7.7.6 -- 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