From patchwork Sat Feb 6 19:12:57 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 579859 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [IPv6:2001:4830:134:3::11]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (No client certificate requested) by ozlabs.org (Postfix) with ESMTPS id E8B0114076E for ; Sun, 7 Feb 2016 06:15:28 +1100 (AEDT) Received: from localhost ([::1]:56047 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aS8KM-0005lQ-S2 for incoming@patchwork.ozlabs.org; Sat, 06 Feb 2016 14:15:26 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53061) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aS8I5-0001Wx-8V for qemu-devel@nongnu.org; Sat, 06 Feb 2016 14:13:06 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aS8I2-0002CG-Ol for qemu-devel@nongnu.org; Sat, 06 Feb 2016 14:13:05 -0500 Received: from mx1.redhat.com ([209.132.183.28]:51791) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aS8I2-0002C6-Gi for qemu-devel@nongnu.org; Sat, 06 Feb 2016 14:13:02 -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 3EDD3C001273; Sat, 6 Feb 2016 19:13:02 +0000 (UTC) Received: from redhat.com (vpn1-5-159.ams2.redhat.com [10.36.5.159]) by int-mx09.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with SMTP id u16JCwlo012025; Sat, 6 Feb 2016 14:12:58 -0500 Date: Sat, 6 Feb 2016 21:12:57 +0200 From: "Michael S. Tsirkin" To: qemu-devel@nongnu.org Message-ID: <1454784308-21177-13-git-send-email-mst@redhat.com> References: <1454784308-21177-1-git-send-email-mst@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <1454784308-21177-1-git-send-email-mst@redhat.com> X-Mutt-Fcc: =sent 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: Cornelia Huck , Peter Maydell , Eduardo Habkost , Vincenzo Maffione , Paolo Bonzini Subject: [Qemu-devel] [PULL v2 12/45] virtio: cache used_idx in a VirtQueue field 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+incoming=patchwork.ozlabs.org@nongnu.org Sender: qemu-devel-bounces+incoming=patchwork.ozlabs.org@nongnu.org From: Vincenzo Maffione Accessing used_idx in the VQ requires an expensive access to guest physical memory. Before this patch, 3 accesses are normally done for each pop/push/notify call. However, since the used_idx is only written by us, we can track it in our internal data structure. Signed-off-by: Vincenzo Maffione Message-Id: <3d062ec54e9a7bf9fb325c1fd693564951f2b319.1450218353.git.v.maffione@gmail.com> Reviewed-by: Cornelia Huck Signed-off-by: Paolo Bonzini Reviewed-by: Michael S. Tsirkin Signed-off-by: Michael S. Tsirkin --- hw/virtio/virtio.c | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c index 225ee6d..82e6414 100644 --- a/hw/virtio/virtio.c +++ b/hw/virtio/virtio.c @@ -71,6 +71,9 @@ struct VirtQueue { VRing vring; uint16_t last_avail_idx; + + uint16_t used_idx; + /* Last used index value we have signalled on */ uint16_t signalled_used; @@ -170,6 +173,7 @@ static inline void vring_used_idx_set(VirtQueue *vq, uint16_t val) hwaddr pa; pa = vq->vring.used + offsetof(VRingUsed, idx); virtio_stw_phys(vq->vdev, pa, val); + vq->used_idx = val; } static inline void vring_used_flags_set_bit(VirtQueue *vq, int mask) @@ -261,7 +265,7 @@ void virtqueue_fill(VirtQueue *vq, const VirtQueueElement *elem, virtqueue_unmap_sg(vq, elem, len); - idx = (idx + vring_used_idx(vq)) % vq->vring.num; + idx = (idx + vq->used_idx) % vq->vring.num; /* Get a pointer to the next entry in the used ring. */ vring_used_ring_id(vq, idx, elem->index); @@ -274,7 +278,7 @@ void virtqueue_flush(VirtQueue *vq, unsigned int count) /* Make sure buffer is written before we update index. */ smp_wmb(); trace_virtqueue_flush(vq, count); - old = vring_used_idx(vq); + old = vq->used_idx; new = old + count; vring_used_idx_set(vq, new); vq->inuse -= count; @@ -782,6 +786,7 @@ void virtio_reset(void *opaque) vdev->vq[i].vring.avail = 0; vdev->vq[i].vring.used = 0; vdev->vq[i].last_avail_idx = 0; + vdev->vq[i].used_idx = 0; virtio_queue_set_vector(vdev, i, VIRTIO_NO_VECTOR); vdev->vq[i].signalled_used = 0; vdev->vq[i].signalled_used_valid = false; @@ -1161,7 +1166,7 @@ static bool vring_notify(VirtIODevice *vdev, VirtQueue *vq) v = vq->signalled_used_valid; vq->signalled_used_valid = true; old = vq->signalled_used; - new = vq->signalled_used = vring_used_idx(vq); + new = vq->signalled_used = vq->used_idx; return !v || vring_need_event(vring_get_used_event(vq), new, old); } @@ -1573,6 +1578,7 @@ int virtio_load(VirtIODevice *vdev, QEMUFile *f, int version_id) vdev->vq[i].last_avail_idx, nheads); return -1; } + vdev->vq[i].used_idx = vring_used_idx(&vdev->vq[i]); } }