From patchwork Thu Nov 29 22:02:56 2012 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: "Michael S. Tsirkin" X-Patchwork-Id: 202832 Return-Path: X-Original-To: incoming@patchwork.ozlabs.org Delivered-To: patchwork-incoming@bilbo.ozlabs.org Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) (using TLSv1 with cipher AES256-SHA (256/256 bits)) (Client did not present a certificate) by ozlabs.org (Postfix) with ESMTPS id 7ED2F2C0094 for ; Fri, 30 Nov 2012 09:01:12 +1100 (EST) Received: from localhost ([::1]:34494 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TeCAP-0006o0-Tl for incoming@patchwork.ozlabs.org; Thu, 29 Nov 2012 17:01:09 -0500 Received: from eggs.gnu.org ([208.118.235.92]:44936) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TeCAI-0006nu-1k for qemu-devel@nongnu.org; Thu, 29 Nov 2012 17:01:03 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TeCAG-00036S-LW for qemu-devel@nongnu.org; Thu, 29 Nov 2012 17:01:01 -0500 Received: from mx1.redhat.com ([209.132.183.28]:45215) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TeCAG-00036F-DA for qemu-devel@nongnu.org; Thu, 29 Nov 2012 17:01:00 -0500 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id qATM0wmh023653 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Thu, 29 Nov 2012 17:00:59 -0500 Received: from redhat.com (vpn1-4-233.ams2.redhat.com [10.36.4.233]) by int-mx01.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with SMTP id qATM03as002128; Thu, 29 Nov 2012 17:00:25 -0500 Date: Fri, 30 Nov 2012 00:02:56 +0200 From: "Michael S. Tsirkin" To: qemu-devel@nongnu.org, stefanha@redhat.com, edivaldoapereira@yahoo.com.br Message-ID: <20121129220256.GA14799@redhat.com> MIME-Version: 1.0 Content-Disposition: inline X-Scanned-By: MIMEDefang 2.67 on 10.5.11.11 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: Amit Shah , Anthony Liguori Subject: [Qemu-devel] [PATCHv2] virtio: limit avail bytes lookahead 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 Commit 0d8d7690850eb0cf2b2b60933cf47669a6b6f18f introduced a regression in virtio-net performance because it looks into the ring aggressively while we really only care about a single packet worth of buffers. Reported as bugzilla 1066055 in launchpad. To fix, add parameters limiting lookahead, and use in virtqueue_avail_bytes. Signed-off-by: Michael S. Tsirkin Reported-by: Edivaldo de Araujo Pereira Tested-by: Edivaldo de Araujo Pereira Reviewed-by: Stefan Hajnoczi --- Anthony says he wants to test this, I only compiled this patch. hw/virtio-rng.c | 12 +++++++++--- hw/virtio-serial-bus.c | 2 +- hw/virtio.c | 15 ++++++++------- hw/virtio.h | 3 ++- 4 files changed, 20 insertions(+), 12 deletions(-) diff --git a/hw/virtio-rng.c b/hw/virtio-rng.c index df329f2..a73ef8e 100644 --- a/hw/virtio-rng.c +++ b/hw/virtio-rng.c @@ -43,11 +43,11 @@ static bool is_guest_ready(VirtIORNG *vrng) return false; } -static size_t get_request_size(VirtQueue *vq) +static size_t get_request_size(VirtQueue *vq, unsigned quota) { unsigned int in, out; - virtqueue_get_avail_bytes(vq, &in, &out); + virtqueue_get_avail_bytes(vq, &in, &out, quota, 0); return in; } @@ -84,12 +84,18 @@ static void chr_read(void *opaque, const void *buf, size_t size) static void virtio_rng_process(VirtIORNG *vrng) { size_t size; + unsigned quota; if (!is_guest_ready(vrng)) { return; } - size = get_request_size(vrng->vq); + if (vrng->quota_remaining < 0) { + quota = 0; + } else { + quota = MIN((uint64_t)vrng->quota_remaining, (uint64_t)UINT32_MAX); + } + size = get_request_size(vrng->vq, quota); size = MIN(vrng->quota_remaining, size); if (size) { rng_backend_request_entropy(vrng->rng, size, chr_read, vrng); diff --git a/hw/virtio-serial-bus.c b/hw/virtio-serial-bus.c index efa8a81..155da58 100644 --- a/hw/virtio-serial-bus.c +++ b/hw/virtio-serial-bus.c @@ -306,7 +306,7 @@ size_t virtio_serial_guest_ready(VirtIOSerialPort *port) if (use_multiport(port->vser) && !port->guest_connected) { return 0; } - virtqueue_get_avail_bytes(vq, &bytes, NULL); + virtqueue_get_avail_bytes(vq, &bytes, NULL, 4096, 0); return bytes; } diff --git a/hw/virtio.c b/hw/virtio.c index ec8b7d8..f40a8c5 100644 --- a/hw/virtio.c +++ b/hw/virtio.c @@ -336,7 +336,8 @@ static unsigned virtqueue_next_desc(hwaddr desc_pa, } void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, - unsigned int *out_bytes) + unsigned int *out_bytes, + unsigned max_in_bytes, unsigned max_out_bytes) { unsigned int idx; unsigned int total_bufs, in_total, out_total; @@ -385,6 +386,9 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, } else { out_total += vring_desc_len(desc_pa, i); } + if (in_total >= max_in_bytes && out_total >= max_out_bytes) { + goto done; + } } while ((i = virtqueue_next_desc(desc_pa, i, max)) != max); if (!indirect) @@ -392,6 +396,7 @@ void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, else total_bufs++; } +done: if (in_bytes) { *in_bytes = in_total; } @@ -405,12 +410,8 @@ int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes, { unsigned int in_total, out_total; - virtqueue_get_avail_bytes(vq, &in_total, &out_total); - if ((in_bytes && in_bytes < in_total) - || (out_bytes && out_bytes < out_total)) { - return 1; - } - return 0; + virtqueue_get_avail_bytes(vq, &in_total, &out_total, in_bytes, out_bytes); + return in_bytes <= in_total && out_bytes <= out_total; } void virtqueue_map_sg(struct iovec *sg, hwaddr *addr, diff --git a/hw/virtio.h b/hw/virtio.h index df8d0f7..7c17f7b 100644 --- a/hw/virtio.h +++ b/hw/virtio.h @@ -150,7 +150,8 @@ int virtqueue_pop(VirtQueue *vq, VirtQueueElement *elem); int virtqueue_avail_bytes(VirtQueue *vq, unsigned int in_bytes, unsigned int out_bytes); void virtqueue_get_avail_bytes(VirtQueue *vq, unsigned int *in_bytes, - unsigned int *out_bytes); + unsigned int *out_bytes, + unsigned max_in_bytes, unsigned max_out_bytes); void virtio_notify(VirtIODevice *vdev, VirtQueue *vq);