From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 75157C43334 for ; Sun, 17 Jul 2022 11:33:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231697AbiGQLdx (ORCPT ); Sun, 17 Jul 2022 07:33:53 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:35884 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230015AbiGQLdv (ORCPT ); Sun, 17 Jul 2022 07:33:51 -0400 Received: from smtp236.sjtu.edu.cn (smtp236.sjtu.edu.cn [202.120.2.236]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 6EDA8DD0 for ; Sun, 17 Jul 2022 04:33:49 -0700 (PDT) Received: from proxy02.sjtu.edu.cn (smtp188.sjtu.edu.cn [202.120.2.188]) by smtp236.sjtu.edu.cn (Postfix) with ESMTPS id 286C01008B388; Sun, 17 Jul 2022 19:33:45 +0800 (CST) Received: from localhost (localhost.localdomain [127.0.0.1]) by proxy02.sjtu.edu.cn (Postfix) with ESMTP id 1729A2007EB67; Sun, 17 Jul 2022 19:33:45 +0800 (CST) X-Virus-Scanned: amavisd-new at Received: from proxy02.sjtu.edu.cn ([127.0.0.1]) by localhost (proxy02.sjtu.edu.cn [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id seTJFmOmQv6T; Sun, 17 Jul 2022 19:33:45 +0800 (CST) Received: from [192.168.24.189] (unknown [202.120.40.82]) (Authenticated sender: qtxuning1999@sjtu.edu.cn) by proxy02.sjtu.edu.cn (Postfix) with ESMTPSA id 3768B200BFDA8; Sun, 17 Jul 2022 19:33:37 +0800 (CST) Message-ID: <47372b7c-15bf-ba9f-083c-e16bd4d1df04@sjtu.edu.cn> Date: Sun, 17 Jul 2022 19:33:37 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v3 2/4] virtio_test: use random length scatterlists to test descriptor chain Content-Language: en-US To: Eugenio Perez Martin Cc: Jason Wang , Michael Tsirkin , virtualization , linux-kernel , Stefano Garzarella References: <20220709022745.21020-1-qtxuning1999@sjtu.edu.cn> <20220709022745.21020-3-qtxuning1999@sjtu.edu.cn> From: Guo Zhi In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2022/7/11 23:35, Eugenio Perez Martin wrote: > On Sat, Jul 9, 2022 at 4:28 AM Guo Zhi wrote: >> Prior implementation only use one descriptor for each io event, which >> does't test code of descriptor chain. More importantly, one descriptor >> will not use indirect feature even indirect feature is specified. Use >> random length scatterlists here to test descriptor chain. >> >> Signed-off-by: Guo Zhi >> --- >> v3: >> - drop fda270fcd virtio_test: move magic number in code as defined constant >> --- >> tools/virtio/virtio_test.c | 11 ++++++++--- >> 1 file changed, 8 insertions(+), 3 deletions(-) >> >> diff --git a/tools/virtio/virtio_test.c b/tools/virtio/virtio_test.c >> index 95f78b311..1408a4a20 100644 >> --- a/tools/virtio/virtio_test.c >> +++ b/tools/virtio/virtio_test.c >> @@ -20,6 +20,7 @@ >> #include "../../drivers/vhost/test.h" >> >> #define RANDOM_BATCH -1 >> +#define MAX_SG_FRAGS 8UL >> >> /* Unused */ >> void *__kmalloc_fake, *__kfree_ignore_start, *__kfree_ignore_end; >> @@ -169,7 +170,8 @@ static void wait_for_interrupt(struct vdev_info *dev) >> static void run_test(struct vdev_info *dev, struct vq_info *vq, >> bool delayed, int batch, int reset_n, int bufs) >> { >> - struct scatterlist sl; >> + struct scatterlist sg[MAX_SG_FRAGS]; >> + int sg_size = 0; >> long started = 0, completed = 0, next_reset = reset_n; >> long completed_before, started_before; >> int r, test = 1; >> @@ -194,8 +196,11 @@ static void run_test(struct vdev_info *dev, struct vq_info *vq, >> >> while (started < bufs && >> (started - completed) < batch) { >> - sg_init_one(&sl, dev->buf, dev->buf_size); >> - r = virtqueue_add_outbuf(vq->vq, &sl, 1, >> + sg_size = random() % (MAX_SG_FRAGS - 1) + 1; > I'm wondering if it would be simpler to reuse batch randomness here, > and make sg_size = MIN(started - completed, MAX_SG_FRAGS). Vhost test > should go faster because the longer chains, and I guess we should hit > a good range of chain lengths with the batch tail anyway. > > Thanks! IMHO, if we reuse batch randomness here, the random length of scatterlist only appears when --batch=random selected. Otherwise, when we have to specify the batch size(eg, 256), the scatterlist( as well as the descriptor chain len) will not be randomed. So I propose decouple the randomness of batch size and descriptor chain length. If we have to achive better performance for vhost_test, just enlarge the MAX_SG_FRAGS is ok. >> + sg_init_table(sg, sg_size); >> + for (int i = 0; i < sg_size; ++i) >> + sg_set_buf(&sg[i], dev->buf + i, 0x1); >> + r = virtqueue_add_outbuf(vq->vq, sg, sg_size, >> dev->buf + started, >> GFP_ATOMIC); >> if (unlikely(r != 0)) { >> -- >> 2.17.1 >>