From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752298AbbCQHJu (ORCPT ); Tue, 17 Mar 2015 03:09:50 -0400 Received: from tama500.ecl.ntt.co.jp ([129.60.39.148]:58861 "EHLO tama500.ecl.ntt.co.jp" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751405AbbCQHJs (ORCPT ); Tue, 17 Mar 2015 03:09:48 -0400 Date: Tue, 17 Mar 2015 16:19:58 +0900 From: Takuya Yoshikawa To: pbonzini@redhat.com Cc: kvm@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH] KVM: Eliminate extra function calls in kvm_get_dirty_log_protect() Message-Id: <20150317161958.991bd7dc36c714f6498821db@lab.ntt.co.jp> X-Mailer: Sylpheed 3.4.2 (GTK+ 2.24.27; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-TM-AS-MML: disable Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org When all bits in mask are not set, kvm_arch_mmu_enable_log_dirty_pt_masked() has nothing to do. But since it needs to be called from the generic code, it cannot be inlined, and a few function calls, two when PML is enabled, are wasted. Since it is common to see many pages remain clean, e.g. framebuffers can stay calm for a long time, it is worth eliminating this overhead. Signed-off-by: Takuya Yoshikawa --- virt/kvm/kvm_main.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index a109370..420d8cf 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -1061,9 +1061,11 @@ int kvm_get_dirty_log_protect(struct kvm *kvm, mask = xchg(&dirty_bitmap[i], 0); dirty_bitmap_buffer[i] = mask; - offset = i * BITS_PER_LONG; - kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot, offset, - mask); + if (mask) { + offset = i * BITS_PER_LONG; + kvm_arch_mmu_enable_log_dirty_pt_masked(kvm, memslot, + offset, mask); + } } spin_unlock(&kvm->mmu_lock); -- 2.1.0