From mboxrd@z Thu Jan 1 00:00:00 1970 From: Xiao Guangrong Subject: [PATCH v3 5/5] KVM: MMU: fast drop all spte on the pte_list Date: Tue, 05 Feb 2013 16:55:37 +0800 Message-ID: <5110C909.1000502@linux.vnet.ibm.com> References: <5110C853.4080705@linux.vnet.ibm.com> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Marcelo Tosatti , Gleb Natapov , LKML , KVM To: Xiao Guangrong Return-path: Received: from e28smtp06.in.ibm.com ([122.248.162.6]:40526 "EHLO e28smtp06.in.ibm.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755177Ab3BEIzo (ORCPT ); Tue, 5 Feb 2013 03:55:44 -0500 Received: from /spool/local by e28smtp06.in.ibm.com with IBM ESMTP SMTP Gateway: Authorized Use Only! Violators will be prosecuted for from ; Tue, 5 Feb 2013 14:23:16 +0530 In-Reply-To: <5110C853.4080705@linux.vnet.ibm.com> Sender: kvm-owner@vger.kernel.org List-ID: If a shadow page is being zapped or a host page is going to be freed, kvm will drop all the reverse-mappings on the shadow page or the gfn. Currently, it drops the reverse-mapping one by one - it deletes the first reverse mapping, then moves other reverse-mapping between the description-table. When the last description-table become empty, it will be freed. It works well if we only have a few reverse-mappings, but some pte_lists are very long, during my tracking, i saw some gfns have more than 200 sptes listed on its pte-list (1G memory in guest on softmmu). Optimization for dropping such long pte-list is worthwhile, at lease it is good for deletion memslots and ksm/thp merge pages. This patch introduce a better way to optimize for this case, it walks all the reverse-mappings and clear them, then free all description-tables together. Signed-off-by: Xiao Guangrong --- arch/x86/kvm/mmu.c | 36 +++++++++++++++++++++++++++--------- 1 files changed, 27 insertions(+), 9 deletions(-) diff --git a/arch/x86/kvm/mmu.c b/arch/x86/kvm/mmu.c index 58f813a..aa7a887 100644 --- a/arch/x86/kvm/mmu.c +++ b/arch/x86/kvm/mmu.c @@ -945,6 +945,25 @@ static void pte_list_remove(u64 *spte, unsigned long *pte_list) } } +static void pte_list_destroy(unsigned long *pte_list) +{ + struct pte_list_desc *desc; + unsigned long list_value = *pte_list; + + *pte_list = 0; + + if (!(list_value & 1)) + return; + + desc = (struct pte_list_desc *)(list_value & ~1ul); + while (desc) { + struct pte_list_desc *next_desc = desc->more; + + mmu_free_pte_list_desc(desc); + desc = next_desc; + } +} + /* * Used by the following functions to iterate through the sptes linked by a * pte_list. All fields are private and not assumed to be used outside. @@ -1183,17 +1202,17 @@ static bool rmap_write_protect(struct kvm *kvm, u64 gfn) static int kvm_unmap_rmapp(struct kvm *kvm, unsigned long *rmapp, struct kvm_memory_slot *slot, unsigned long data) { - u64 *sptep; struct pte_list_iterator iter; + u64 *sptep; int need_tlb_flush = 0; -restart: for_each_spte_in_rmap(*rmapp, iter, sptep) { - drop_spte(kvm, sptep); + mmu_spte_clear_track_bits(sptep); need_tlb_flush = 1; - goto restart; } + pte_list_destroy(rmapp); + return need_tlb_flush; } @@ -2016,11 +2035,10 @@ static void kvm_mmu_unlink_parents(struct kvm *kvm, struct kvm_mmu_page *sp) u64 *sptep; struct pte_list_iterator iter; -restart: - for_each_spte_in_pte_list(sp->parent_ptes, iter, sptep) { - drop_parent_pte(sp, sptep); - goto restart; - } + for_each_spte_in_pte_list(sp->parent_ptes, iter, sptep) + mmu_spte_clear_no_track(sptep); + + pte_list_destroy(&sp->parent_ptes); } static int mmu_zap_unsync_children(struct kvm *kvm, -- 1.7.7.6