From patchwork Mon Dec 1 17:29:25 2014 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Igor Mammedov X-Patchwork-Id: 5414521 Return-Path: X-Original-To: patchwork-kvm@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork2.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.19.201]) by patchwork2.web.kernel.org (Postfix) with ESMTP id C6CCBBEEA8 for ; Mon, 1 Dec 2014 17:30:15 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 152E72026F for ; Mon, 1 Dec 2014 17:30:15 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 40FB120266 for ; Mon, 1 Dec 2014 17:30:14 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754101AbaLAR3k (ORCPT ); Mon, 1 Dec 2014 12:29:40 -0500 Received: from mx1.redhat.com ([209.132.183.28]:55703 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754093AbaLAR3i (ORCPT ); Mon, 1 Dec 2014 12:29:38 -0500 Received: from int-mx11.intmail.prod.int.phx2.redhat.com (int-mx11.intmail.prod.int.phx2.redhat.com [10.5.11.24]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id sB1HTcAL001779 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=FAIL); Mon, 1 Dec 2014 12:29:38 -0500 Received: from dell-pet610-01.lab.eng.brq.redhat.com (dell-pet610-01.lab.eng.brq.redhat.com [10.34.42.20]) by int-mx11.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id sB1HTXAx025856; Mon, 1 Dec 2014 12:29:37 -0500 From: Igor Mammedov To: linux-kernel@vger.kernel.org Cc: pbonzini@redhat.com, kvm@vger.kernel.org Subject: [PATCH 3/5] kvm: search_memslots: add simple LRU memslot caching Date: Mon, 1 Dec 2014 17:29:25 +0000 Message-Id: <1417454967-4465-4-git-send-email-imammedo@redhat.com> In-Reply-To: <1417454967-4465-1-git-send-email-imammedo@redhat.com> References: <1417454967-4465-1-git-send-email-imammedo@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.24 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, T_RP_MATCHES_RCVD, UNPARSEABLE_RELAY autolearn=unavailable version=3.3.1 X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on mail.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP In typical guest boot workload only 2-3 memslots are used extensively, and at that it's mostly the same memslot lookup operation. Adding LRU cache improves average lookup time from 46 to 28 cycles (~40%) for this workload. Signed-off-by: Igor Mammedov --- include/linux/kvm_host.h | 12 ++++++++++-- 1 file changed, 10 insertions(+), 2 deletions(-) diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 231dd94..1a37144 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -353,6 +353,7 @@ struct kvm_memslots { struct kvm_memory_slot memslots[KVM_MEM_SLOTS_NUM]; /* The mapping table from slot id to the index in memslots[]. */ short id_to_index[KVM_MEM_SLOTS_NUM]; + atomic_t lru_slot; }; struct kvm { @@ -790,12 +791,19 @@ static inline void kvm_guest_exit(void) static inline struct kvm_memory_slot * search_memslots(struct kvm_memslots *slots, gfn_t gfn) { - struct kvm_memory_slot *memslot; + int slot = atomic_read(&slots->lru_slot); + struct kvm_memory_slot *memslot = &slots->memslots[slot]; + + if (gfn >= memslot->base_gfn && + gfn < memslot->base_gfn + memslot->npages) + return memslot; kvm_for_each_memslot(memslot, slots) if (gfn >= memslot->base_gfn && - gfn < memslot->base_gfn + memslot->npages) + gfn < memslot->base_gfn + memslot->npages) { + atomic_set(&slots->lru_slot, memslot - slots->memslots); return memslot; + } return NULL; }