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 mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1CDA4C433F5 for ; Wed, 27 Oct 2021 19:37:14 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [140.211.166.137]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id AA3C560EFE for ; Wed, 27 Oct 2021 19:37:13 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org AA3C560EFE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=lists.linux-foundation.org Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 666ED4056A; Wed, 27 Oct 2021 19:37:13 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id C9ldGQWDCgRB; Wed, 27 Oct 2021 19:37:12 +0000 (UTC) Received: from lists.linuxfoundation.org (lf-lists.osuosl.org [IPv6:2605:bc80:3010:104::8cd3:938]) by smtp4.osuosl.org (Postfix) with ESMTPS id BBBCE40562; Wed, 27 Oct 2021 19:37:11 +0000 (UTC) Received: from lf-lists.osuosl.org (localhost [127.0.0.1]) by lists.linuxfoundation.org (Postfix) with ESMTP id 96108C0012; Wed, 27 Oct 2021 19:37:11 +0000 (UTC) Received: from smtp4.osuosl.org (smtp4.osuosl.org [IPv6:2605:bc80:3010::137]) by lists.linuxfoundation.org (Postfix) with ESMTP id 5B433C000E for ; Wed, 27 Oct 2021 19:37:10 +0000 (UTC) Received: from localhost (localhost [127.0.0.1]) by smtp4.osuosl.org (Postfix) with ESMTP id 4410B40564 for ; Wed, 27 Oct 2021 19:37:10 +0000 (UTC) X-Virus-Scanned: amavisd-new at osuosl.org Received: from smtp4.osuosl.org ([127.0.0.1]) by localhost (smtp4.osuosl.org [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id hZOPSZXLtWlo for ; Wed, 27 Oct 2021 19:37:09 +0000 (UTC) X-Greylist: domain auto-whitelisted by SQLgrey-1.8.0 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by smtp4.osuosl.org (Postfix) with ESMTPS id 4A37140562 for ; Wed, 27 Oct 2021 19:37:09 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1635363428; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=TyWbseVcIvJiB/y7F+AQk9e5SoEkEaCHQO94xB0lAow=; b=VKnh0LJh3aqvGODUX8F8oMY7C2Vo32IbAYvNYwK7H8XbaCmyhvzC44fdY2VCfBpD9NCme5 cnb8ryp11P6UK2Orul2kEhS9CpMw7YP93SiIXRnifqdngT913TrJzKmcTpps0NJzgWBaEb mUTUuVoGbOZGWlgT3RuLPYgZkHpJK+g= Received: from mail-ed1-f72.google.com (mail-ed1-f72.google.com [209.85.208.72]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-467-FFs_zESIO2qJui98RxHnqA-1; Wed, 27 Oct 2021 15:37:04 -0400 X-MC-Unique: FFs_zESIO2qJui98RxHnqA-1 Received: by mail-ed1-f72.google.com with SMTP id m16-20020a056402431000b003dd2005af01so3330528edc.5 for ; Wed, 27 Oct 2021 12:37:04 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=TyWbseVcIvJiB/y7F+AQk9e5SoEkEaCHQO94xB0lAow=; b=RsQv2tqSWMh9+u9x2DuW8i9ahchlbBfWlus76GjJHq2eKRWe6MOKYW46mA/bZ3M4IG IKnL022V2xhcAWyV9+t3KQcyrCCu1WlmJb/zmstRwNuRJkFWMApveatQT4tbmszKobPe TNX9Jdc01XWaDZcOWGwKehG/os+MyLCWGmW1OmKspS2oaiMiFAXZ7IOmc95mgAnzxwj8 TbJ8Ga1H0qPtMxSCqFUkiQYqIDv+zZPBvr+Ck6jCGm0vvCpfImp0a83TohqfwAumZT7k 1N+XOIMXcAslb6YBHqXGAV5KEEXjorlb3gYVCp7G3rlYYu+dhbhcXf3AltSGTJBAovNj badg== X-Gm-Message-State: AOAM5310zXsG0j06Fev3Lu4h1yhWIG/3wjTagtkoMd8pTpGJF6ORWCHh tpQtdZzWxQMjV/8HDMrKgfbumNt+pnvo17TRsz/Hl4RBD26F0pfC5/houuVkbcklqR2m8TJ1c8u wvYG26XDURZHpSh8MYq8cbHrlpVYBIgGJQga7+noD0Q== X-Received: by 2002:a05:6402:10cd:: with SMTP id p13mr41189087edu.111.1635363423399; Wed, 27 Oct 2021 12:37:03 -0700 (PDT) X-Google-Smtp-Source: ABdhPJwaqOD6uea1lUYf7AdF5P8EDeIgspaeRBq2vHi/VPjOWrW95ZNai33V1+zqnc+0wZyHKtsfxQ== X-Received: by 2002:a05:6402:10cd:: with SMTP id p13mr41189060edu.111.1635363423177; Wed, 27 Oct 2021 12:37:03 -0700 (PDT) Received: from redhat.com ([2.55.137.59]) by smtp.gmail.com with ESMTPSA id gt36sm405080ejc.13.2021.10.27.12.37.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Oct 2021 12:37:02 -0700 (PDT) Date: Wed, 27 Oct 2021 15:36:58 -0400 From: "Michael S. Tsirkin" To: Dongli Zhang Subject: Re: [PATCH 1/3] virtio: cache indirect desc for split Message-ID: <20211027153545-mutt-send-email-mst@kernel.org> References: <20211027061913.76276-1-xuanzhuo@linux.alibaba.com> <20211027061913.76276-2-xuanzhuo@linux.alibaba.com> MIME-Version: 1.0 In-Reply-To: Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=mst@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Disposition: inline Cc: netdev@vger.kernel.org, virtualization@lists.linux-foundation.org, "David S. Miller" , Jakub Kicinski X-BeenThere: virtualization@lists.linux-foundation.org X-Mailman-Version: 2.1.15 Precedence: list List-Id: Linux virtualization List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Errors-To: virtualization-bounces@lists.linux-foundation.org Sender: "Virtualization" On Wed, Oct 27, 2021 at 09:33:46AM -0700, Dongli Zhang wrote: > > > On 10/26/21 11:19 PM, Xuan Zhuo wrote: > > In the case of using indirect, indirect desc must be allocated and > > released each time, which increases a lot of cpu overhead. > > > > Here, a cache is added for indirect. If the number of indirect desc to be > > applied for is less than VIRT_QUEUE_CACHE_DESC_NUM, the desc array with > > the size of VIRT_QUEUE_CACHE_DESC_NUM is fixed and cached for reuse. > > > > Signed-off-by: Xuan Zhuo > > --- > > drivers/virtio/virtio.c | 6 ++++ > > drivers/virtio/virtio_ring.c | 63 ++++++++++++++++++++++++++++++------ > > include/linux/virtio.h | 10 ++++++ > > 3 files changed, 70 insertions(+), 9 deletions(-) > > > > diff --git a/drivers/virtio/virtio.c b/drivers/virtio/virtio.c > > index 0a5b54034d4b..04bcb74e5b9a 100644 > > --- a/drivers/virtio/virtio.c > > +++ b/drivers/virtio/virtio.c > > @@ -431,6 +431,12 @@ bool is_virtio_device(struct device *dev) > > } > > EXPORT_SYMBOL_GPL(is_virtio_device); > > > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val) > > +{ > > + dev->desc_cache = val; > > +} > > +EXPORT_SYMBOL_GPL(virtio_use_desc_cache); > > + > > void unregister_virtio_device(struct virtio_device *dev) > > { > > int index = dev->index; /* save for after device release */ > > diff --git a/drivers/virtio/virtio_ring.c b/drivers/virtio/virtio_ring.c > > index dd95dfd85e98..0b9a8544b0e8 100644 > > --- a/drivers/virtio/virtio_ring.c > > +++ b/drivers/virtio/virtio_ring.c > > @@ -117,6 +117,10 @@ struct vring_virtqueue { > > /* Hint for event idx: already triggered no need to disable. */ > > bool event_triggered; > > > > + /* Is indirect cache used? */ > > + bool use_desc_cache; > > + void *desc_cache_chain; > > + > > union { > > /* Available for split ring */ > > struct { > > @@ -423,12 +427,47 @@ static unsigned int vring_unmap_one_split(const struct vring_virtqueue *vq, > > return extra[i].next; > > } > > > > -static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > > +#define VIRT_QUEUE_CACHE_DESC_NUM 4 > > + > > +static void desc_cache_chain_free_split(void *chain) > > +{ > > + struct vring_desc *desc; > > + > > + while (chain) { > > + desc = chain; > > + chain = (void *)desc->addr; > > + kfree(desc); > > + } > > +} > > + > > +static void desc_cache_put_split(struct vring_virtqueue *vq, > > + struct vring_desc *desc, int n) > > +{ > > + if (vq->use_desc_cache && n <= VIRT_QUEUE_CACHE_DESC_NUM) { > > + desc->addr = (u64)vq->desc_cache_chain; > > + vq->desc_cache_chain = desc; > > + } else { > > + kfree(desc); > > + } > > +} > > + > > +static struct vring_desc *alloc_indirect_split(struct vring_virtqueue *vq, > > unsigned int total_sg, > > gfp_t gfp) > > { > > struct vring_desc *desc; > > - unsigned int i; > > + unsigned int i, n; > > + > > + if (vq->use_desc_cache && total_sg <= VIRT_QUEUE_CACHE_DESC_NUM) { > > + if (vq->desc_cache_chain) { > > + desc = vq->desc_cache_chain; > > + vq->desc_cache_chain = (void *)desc->addr; > > + goto got; > > + } > > + n = VIRT_QUEUE_CACHE_DESC_NUM; > > How about to make the VIRT_QUEUE_CACHE_DESC_NUM configurable (at least during > driver probing) unless there is a reason that the default value is 4. > > Thank you very much! > > Dongli Zhang I would start with some experimentation showing that it actually makes a difference in performance. > > > > + } else { > > + n = total_sg; > > + } > > > > /* > > * We require lowmem mappings for the descriptors because > > @@ -437,12 +476,13 @@ static struct vring_desc *alloc_indirect_split(struct virtqueue *_vq, > > */ > > gfp &= ~__GFP_HIGHMEM; > > > > - desc = kmalloc_array(total_sg, sizeof(struct vring_desc), gfp); > > + desc = kmalloc_array(n, sizeof(struct vring_desc), gfp); > > if (!desc) > > return NULL; > > > > +got: > > for (i = 0; i < total_sg; i++) > > - desc[i].next = cpu_to_virtio16(_vq->vdev, i + 1); > > + desc[i].next = cpu_to_virtio16(vq->vq.vdev, i + 1); > > return desc; > > } > > > > @@ -508,7 +548,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > head = vq->free_head; > > > > if (virtqueue_use_indirect(_vq, total_sg)) > > - desc = alloc_indirect_split(_vq, total_sg, gfp); > > + desc = alloc_indirect_split(vq, total_sg, gfp); > > else { > > desc = NULL; > > WARN_ON_ONCE(total_sg > vq->split.vring.num && !vq->indirect); > > @@ -652,7 +692,7 @@ static inline int virtqueue_add_split(struct virtqueue *_vq, > > } > > > > if (indirect) > > - kfree(desc); > > + desc_cache_put_split(vq, desc, total_sg); > > > > END_USE(vq); > > return -ENOMEM; > > @@ -717,7 +757,7 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > > if (vq->indirect) { > > struct vring_desc *indir_desc = > > vq->split.desc_state[head].indir_desc; > > - u32 len; > > + u32 len, n; > > > > /* Free the indirect table, if any, now that it's unmapped. */ > > if (!indir_desc) > > @@ -729,10 +769,12 @@ static void detach_buf_split(struct vring_virtqueue *vq, unsigned int head, > > VRING_DESC_F_INDIRECT)); > > BUG_ON(len == 0 || len % sizeof(struct vring_desc)); > > > > - for (j = 0; j < len / sizeof(struct vring_desc); j++) > > + n = len / sizeof(struct vring_desc); > > + > > + for (j = 0; j < n; j++) > > vring_unmap_one_split_indirect(vq, &indir_desc[j]); > > > > - kfree(indir_desc); > > + desc_cache_put_split(vq, indir_desc, n); > > vq->split.desc_state[head].indir_desc = NULL; > > } else if (ctx) { > > *ctx = vq->split.desc_state[head].indir_desc; > > @@ -2199,6 +2241,8 @@ struct virtqueue *__vring_new_virtqueue(unsigned int index, > > vq->indirect = virtio_has_feature(vdev, VIRTIO_RING_F_INDIRECT_DESC) && > > !context; > > vq->event = virtio_has_feature(vdev, VIRTIO_RING_F_EVENT_IDX); > > + vq->desc_cache_chain = NULL; > > + vq->use_desc_cache = vdev->desc_cache; > > > > if (virtio_has_feature(vdev, VIRTIO_F_ORDER_PLATFORM)) > > vq->weak_barriers = false; > > @@ -2329,6 +2373,7 @@ void vring_del_virtqueue(struct virtqueue *_vq) > > if (!vq->packed_ring) { > > kfree(vq->split.desc_state); > > kfree(vq->split.desc_extra); > > + desc_cache_chain_free_split(vq->desc_cache_chain); > > } > > kfree(vq); > > } > > diff --git a/include/linux/virtio.h b/include/linux/virtio.h > > index 41edbc01ffa4..d84b7b8f4070 100644 > > --- a/include/linux/virtio.h > > +++ b/include/linux/virtio.h > > @@ -109,6 +109,7 @@ struct virtio_device { > > bool failed; > > bool config_enabled; > > bool config_change_pending; > > + bool desc_cache; > > spinlock_t config_lock; > > spinlock_t vqs_list_lock; /* Protects VQs list access */ > > struct device dev; > > @@ -130,6 +131,15 @@ int register_virtio_device(struct virtio_device *dev); > > void unregister_virtio_device(struct virtio_device *dev); > > bool is_virtio_device(struct device *dev); > > > > +/** > > + * virtio_use_desc_cache - virtio ring use desc cache > > + * > > + * virtio will cache the allocated indirect desc. > > + * > > + * This function must be called before find_vqs. > > + */ > > +void virtio_use_desc_cache(struct virtio_device *dev, bool val); > > + > > void virtio_break_device(struct virtio_device *dev); > > > > void virtio_config_changed(struct virtio_device *dev); > > _______________________________________________ Virtualization mailing list Virtualization@lists.linux-foundation.org https://lists.linuxfoundation.org/mailman/listinfo/virtualization