On 04/19/2011 02:38 AM, Takuya Yoshikawa wrote: > From: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx> > > We optimize multi level guest page table walk as follows: > > 1. We cache the memslot which, probably, includes the next guest page > tables to avoid searching for it many times. Yeah, the hit is very high, after optimizing the algorithm of memslots (http://lwn.net/Articles/429308/), maybe the advantage is not so significant, could you apply this patchset and test again please? > 2. We use get_user() instead of copy_from_user(). > > Note that this is kind of a restricted way of Xiao's more generic > work: "KVM: optimize memslots searching and cache GPN to GFN." > > With this patch applied, paging64_walk_addr_generic() has improved > as the following tracing results show. > > Before: > 3.169 us | paging64_walk_addr_generic(); > 1.880 us | paging64_walk_addr_generic(); > 1.243 us | paging64_walk_addr_generic(); > 1.517 us | paging64_walk_addr_generic(); > 3.009 us | paging64_walk_addr_generic(); > 1.814 us | paging64_walk_addr_generic(); > 1.340 us | paging64_walk_addr_generic(); > 1.659 us | paging64_walk_addr_generic(); > 1.748 us | paging64_walk_addr_generic(); > 1.488 us | paging64_walk_addr_generic(); > > After: > 1.714 us | paging64_walk_addr_generic(); > 0.806 us | paging64_walk_addr_generic(); > 0.664 us | paging64_walk_addr_generic(); > 0.619 us | paging64_walk_addr_generic(); > 0.645 us | paging64_walk_addr_generic(); > 0.605 us | paging64_walk_addr_generic(); > 1.388 us | paging64_walk_addr_generic(); > 0.753 us | paging64_walk_addr_generic(); > 0.594 us | paging64_walk_addr_generic(); > 0.833 us | paging64_walk_addr_generic(); > > Signed-off-by: Takuya Yoshikawa <yoshikawa.takuya@xxxxxxxxxxxxx> > --- > arch/x86/kvm/paging_tmpl.h | 37 ++++++++++++++++++++++++++++++++----- > 1 files changed, 32 insertions(+), 5 deletions(-) > > diff --git a/arch/x86/kvm/paging_tmpl.h b/arch/x86/kvm/paging_tmpl.h > index 109939a..614aa3f 100644 > --- a/arch/x86/kvm/paging_tmpl.h > +++ b/arch/x86/kvm/paging_tmpl.h > @@ -109,12 +109,37 @@ static unsigned FNAME(gpte_access)(struct kvm_vcpu *vcpu, pt_element_t gpte) > return access; > } > > +/* > + * Read the guest PTE refered to by table_gfn and offset and put it into ptep. > + * > + * *slot_hint, if not NULL, should point to a memslot which probably includes > + * the guest PTE. The actual memslot will be put back into this so that > + * callers can cache it. > + */ > static int FNAME(read_guest_pte)(struct kvm_vcpu *vcpu, struct kvm_mmu *mmu, > - gfn_t table_gfn, int offset, pt_element_t *ptep) > + gfn_t table_gfn, int offset, pt_element_t *ptep, > + struct kvm_memory_slot **slot_hint) > { > - return kvm_read_guest_page_mmu(vcpu, mmu, table_gfn, ptep, > - offset, sizeof(*ptep), > - PFERR_USER_MASK | PFERR_WRITE_MASK); > + unsigned long addr; > + pt_element_t __user *ptep_user; > + gfn_t real_gfn; > + > + real_gfn = mmu->translate_gpa(vcpu, gfn_to_gpa(table_gfn), > + PFERR_USER_MASK | PFERR_WRITE_MASK); > + if (real_gfn == UNMAPPED_GVA) > + return -EFAULT; > + > + real_gfn = gpa_to_gfn(real_gfn); > + > + if (!(*slot_hint) || !gfn_in_memslot(*slot_hint, real_gfn)) > + *slot_hint = gfn_to_memslot(vcpu->kvm, real_gfn); > + You forgot to check the result. (if *slot_hint == NULL)? ...ã;-) -- 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
