From patchwork Tue Mar 1 06:18:24 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Fam Zheng X-Patchwork-Id: 8462201 Return-Path: X-Original-To: patchwork-qemu-devel@patchwork.kernel.org Delivered-To: patchwork-parsemail@patchwork1.web.kernel.org Received: from mail.kernel.org (mail.kernel.org [198.145.29.136]) by patchwork1.web.kernel.org (Postfix) with ESMTP id 2EE6E9F38C for ; Tue, 1 Mar 2016 06:22:52 +0000 (UTC) Received: from mail.kernel.org (localhost [127.0.0.1]) by mail.kernel.org (Postfix) with ESMTP id 8BB90202C8 for ; Tue, 1 Mar 2016 06:22:51 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id D1620202AE for ; Tue, 1 Mar 2016 06:22:50 +0000 (UTC) Received: from localhost ([::1]:41183 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aadhq-0002cG-6Z for patchwork-qemu-devel@patchwork.kernel.org; Tue, 01 Mar 2016 01:22:50 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:45052) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aadeO-0005Yw-DK for qemu-devel@nongnu.org; Tue, 01 Mar 2016 01:19:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aadeL-0005za-Nv for qemu-devel@nongnu.org; Tue, 01 Mar 2016 01:19:16 -0500 Received: from mx1.redhat.com ([209.132.183.28]:41089) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aadeL-0005zU-Gk for qemu-devel@nongnu.org; Tue, 01 Mar 2016 01:19:13 -0500 Received: from int-mx09.intmail.prod.int.phx2.redhat.com (int-mx09.intmail.prod.int.phx2.redhat.com [10.5.11.22]) by mx1.redhat.com (Postfix) with ESMTPS id 33ACDC06C9FC; Tue, 1 Mar 2016 06:19:13 +0000 (UTC) Received: from fam-t430.redhat.com (vpn1-5-42.pek2.redhat.com [10.72.5.42]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id u216IPXe031427; Tue, 1 Mar 2016 01:19:08 -0500 From: Fam Zheng To: qemu-devel@nongnu.org Date: Tue, 1 Mar 2016 14:18:24 +0800 Message-Id: <1456813104-25902-8-git-send-email-famz@redhat.com> In-Reply-To: <1456813104-25902-1-git-send-email-famz@redhat.com> References: <1456813104-25902-1-git-send-email-famz@redhat.com> X-Scanned-By: MIMEDefang 2.68 on 10.5.11.22 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Paolo Bonzini , arei.gonglei@huawei.com, peterx@redhat.com Subject: [Qemu-devel] [PATCH v2 7/7] exec: Introduce AddressSpaceDispatch.mru_section X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org Sender: qemu-devel-bounces+patchwork-qemu-devel=patchwork.kernel.org@nongnu.org X-Spam-Status: No, score=-6.9 required=5.0 tests=BAYES_00, RCVD_IN_DNSWL_HI, 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 Under heavy workloads the lookup will likely end up with the same MemoryRegionSection from last time. Using a pointer to cache the result, like ram_list.mru_block, significantly reduces cost of address_space_translate. During address space topology update, as->dispatch will be reallocated so the pointer is invalidated automatically. Perf reports a visible drop on the cpu usage, because phys_page_find is not called. Before: 2.35% qemu-system-x86_64 [.] phys_page_find 0.97% qemu-system-x86_64 [.] address_space_translate_internal 0.95% qemu-system-x86_64 [.] address_space_translate 0.55% qemu-system-x86_64 [.] address_space_lookup_region After: 0.97% qemu-system-x86_64 [.] address_space_translate_internal 0.97% qemu-system-x86_64 [.] address_space_lookup_region 0.84% qemu-system-x86_64 [.] address_space_translate Signed-off-by: Fam Zheng --- exec.c | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) diff --git a/exec.c b/exec.c index b4e2eb5..98d7733 100644 --- a/exec.c +++ b/exec.c @@ -135,6 +135,7 @@ typedef struct PhysPageMap { struct AddressSpaceDispatch { struct rcu_head rcu; + MemoryRegionSection *mru_section; /* This is a multi-level map on the physical address space. * The bottom level has pointers to MemoryRegionSections. */ @@ -350,14 +351,25 @@ static MemoryRegionSection *address_space_lookup_region(AddressSpaceDispatch *d, hwaddr addr, bool resolve_subpage) { - MemoryRegionSection *section; + MemoryRegionSection *section = atomic_read(&d->mru_section); subpage_t *subpage; + bool update; - section = phys_page_find(d->phys_map, addr, d->map.nodes, d->map.sections); + if (section && section != &d->map.sections[PHYS_SECTION_UNASSIGNED] && + section_covers_addr(section, addr)) { + update = false; + } else { + section = phys_page_find(d->phys_map, addr, d->map.nodes, + d->map.sections); + update = true; + } if (resolve_subpage && section->mr->subpage) { subpage = container_of(section->mr, subpage_t, iomem); section = &d->map.sections[subpage->sub_section[SUBPAGE_IDX(addr)]]; } + if (update) { + atomic_set(&d->mru_section, section); + } return section; }