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 0C9C9C433EF for ; Wed, 27 Oct 2021 08:55:26 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DA6E761040 for ; Wed, 27 Oct 2021 08:55:25 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235938AbhJ0I5t (ORCPT ); Wed, 27 Oct 2021 04:57:49 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:59422 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231566AbhJ0I5t (ORCPT ); Wed, 27 Oct 2021 04:57:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1635324924; 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=Rd+1bM1NgvdCjYjFOKUmVGZTFl4DME6r0n7GbWzwCwA=; b=L/1T9AkmyLcha3+Gu7LfrfTUliJcUo7ZhQsX2S4gpKC9AK7LDcRDiUz1QIhM5GYpKnrC0W Z8sI+pnCUXqtwV8JlZNzvXQRtNAlDbU7zpj0CofYwRDjNkQ65nJuEpuWgLwXDGSvKaND5n R6neq8b5rtwhYupL2S2rjT/CwtlMX2Q= Received: from mail-wr1-f71.google.com (mail-wr1-f71.google.com [209.85.221.71]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-160-xzUD7dRJPu-2pGu7QdhR2Q-1; Wed, 27 Oct 2021 04:55:22 -0400 X-MC-Unique: xzUD7dRJPu-2pGu7QdhR2Q-1 Received: by mail-wr1-f71.google.com with SMTP id f1-20020a5d64c1000000b001611832aefeso400979wri.17 for ; Wed, 27 Oct 2021 01:55:22 -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=Rd+1bM1NgvdCjYjFOKUmVGZTFl4DME6r0n7GbWzwCwA=; b=GpNPjQXR/HtWLKccyBR7jCXSFLZjDqsT1TG6W8ZFXHtqP4NrERFoTcMENXEHlbaavi Nrt/sQbFPSYV4V17W+bBF/vaUqheuO5kA3OSZu582XMpwXX+xvB+u0IsNFMo7+aAxHlm x6bJdgidPST8lFRwFyThVjBqyaZm/cUIvWr4xrisuPFzhr9IrkgyRMlzOsQ+/eG0eyCk JeEnoGwhJPe2wolrIA79Uu/8FPbmnjLKdlHhTDOEp8/nRv3KACIIuKaUYm4UypGnKZ+g HI+MeKDzkCdp7HExxUfTeZ42L4jR5nVOIU65I6GFmmsOAwkkbxnST6bgydIxibxLTtOd qEYA== X-Gm-Message-State: AOAM533ZVh5PH/syv9rzbyobh/6mkFBwzprv6qoSXxbKlCdhEsC00VTO mdtlTsyECw7angY2MtEIejcpWKZykHPU6+WU0fwWgPLl8c+L4PxBHlBhwbKmybVfUA41CRciRjn 3N9BA0WrvU9OaZGEv X-Received: by 2002:a5d:570c:: with SMTP id a12mr6556404wrv.418.1635324921464; Wed, 27 Oct 2021 01:55:21 -0700 (PDT) X-Google-Smtp-Source: ABdhPJzc0w1MFCM+zX4dw5/ef/iVgg5fZjAkE2o0ExvenlNFpYGQ7DD5QS1tyRk29+AUahZaPh7fmw== X-Received: by 2002:a5d:570c:: with SMTP id a12mr6556379wrv.418.1635324921130; Wed, 27 Oct 2021 01:55:21 -0700 (PDT) Received: from redhat.com ([2a03:c5c0:207e:a543:72f:c4d1:8911:6346]) by smtp.gmail.com with ESMTPSA id f9sm10848012wrx.31.2021.10.27.01.55.18 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 27 Oct 2021 01:55:20 -0700 (PDT) Date: Wed, 27 Oct 2021 04:55:16 -0400 From: "Michael S. Tsirkin" To: Xuan Zhuo Cc: virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, Jason Wang , "David S. Miller" , Jakub Kicinski Subject: Re: [PATCH 1/3] virtio: cache indirect desc for split Message-ID: <20211027043851-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 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20211027061913.76276-2-xuanzhuo@linux.alibaba.com> Precedence: bulk List-ID: X-Mailing-List: netdev@vger.kernel.org On Wed, Oct 27, 2021 at 02:19:11PM +0800, 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 { Let's use llist_head and friends please (I am guessing we want single-linked to avoid writing into indirect buffer after use, invalidating the cache, but please document why in a comment). Do not open-code it. Also hide all casts in inline wrappers. > @@ -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 Add an inline wrapper for checking sg versus VIRT_QUEUE_CACHE_DESC_NUM. > + > +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; Hmm. This will allocate more entries than actually used. Why do it? > + } 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); > -- > 2.31.0