| Message ID | 1430393772-27208-3-git-send-email-pbonzini@redhat.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
Paolo Bonzini <pbonzini@redhat.com> writes: > From: Radim Kr?má? <rkrcmar@redhat.com> > > Saves one O(log N) search. It really doesn't hurt to change this to: "Caching memslot value helps us avoid another O(log N) search later when calling mark_page_dirty_in_slot()." Sorry I am not a fan of commit messages less than 75 characters :) Or you can also call me dumb :) > Signed-off-by: Radim Kr?má? <rkrcmar@redhat.com> > Message-Id: <1428695247-27603-1-git-send-email-rkrcmar@redhat.com> > Signed-off-by: Paolo Bonzini <pbonzini@redhat.com> > --- > virt/kvm/kvm_main.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c > index 90977418aeb6..b6d415156283 100644 > --- a/virt/kvm/kvm_main.c > +++ b/virt/kvm/kvm_main.c > @@ -1590,15 +1590,17 @@ int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data, > int offset, int len) > { > int r; > + struct kvm_memory_slot *memslot; > unsigned long addr; > > - addr = gfn_to_hva(kvm, gfn); > + memslot = gfn_to_memslot(kvm, gfn); > + addr = gfn_to_hva_memslot(memslot, gfn); > if (kvm_is_error_hva(addr)) > return -EFAULT; > r = __copy_to_user((void __user *)addr + offset, data, len); > if (r) > return -EFAULT; > - mark_page_dirty(kvm, gfn); > + mark_page_dirty_in_slot(kvm, memslot, gfn); > return 0; > } > EXPORT_SYMBOL_GPL(kvm_write_guest_page); -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
2015-05-05 11:03-0400, Bandan Das: > Paolo Bonzini <pbonzini@redhat.com> writes: > >> From: Radim Kr?má? <rkrcmar@redhat.com> >> >> Saves one O(log N) search. > > It really doesn't hurt to change this to: > "Caching memslot value helps us avoid another O(log N) search > later when calling mark_page_dirty_in_slot()." > > Sorry I am not a fan of commit messages less than 75 characters :) Sure, I just couldn't find a message that would be easier to understand than the code and not misleading at the same time ... what came out was a teaser for people who care about performance :) In verbose mode, I'd write it like this: gfn_to_hva() and mark_page_dirty() both call gfn_to_memslot(). We can store a result of gfn_to_memslot() (memslot) and unwrap gfn_to_hva() and mark_page_dirty() to directly call functions that accept a memslot. gfn_to_memslot() does a binary search, so it also saves some cycles. -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 90977418aeb6..b6d415156283 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1590,15 +1590,17 @@ int kvm_write_guest_page(struct kvm *kvm, gfn_t gfn, const void *data, int offset, int len) { int r; + struct kvm_memory_slot *memslot; unsigned long addr; - addr = gfn_to_hva(kvm, gfn); + memslot = gfn_to_memslot(kvm, gfn); + addr = gfn_to_hva_memslot(memslot, gfn); if (kvm_is_error_hva(addr)) return -EFAULT; r = __copy_to_user((void __user *)addr + offset, data, len); if (r) return -EFAULT; - mark_page_dirty(kvm, gfn); + mark_page_dirty_in_slot(kvm, memslot, gfn); return 0; } EXPORT_SYMBOL_GPL(kvm_write_guest_page);