From: David Marchand <david.marchand@redhat.com>
To: Xuan Ding <xuan.ding@intel.com>
Cc: Maxime Coquelin <maxime.coquelin@redhat.com>,
"Xia, Chenbo" <chenbo.xia@intel.com>, dev <dev@dpdk.org>,
Jiayu Hu <jiayu.hu@intel.com>,
Cheng Jiang <cheng1.jiang@intel.com>,
Sunil Pai G <sunil.pai.g@intel.com>,
liangma@liangbit.com, Yuan Wang <yuanx.wang@intel.com>,
"Mcnamara, John" <john.mcnamara@intel.com>
Subject: Re: [PATCH v8 4/5] vhost: support async dequeue for split ring
Date: Thu, 16 Jun 2022 16:40:07 +0200 [thread overview]
Message-ID: <CAJFAV8xyyn7rAQ5pN994h9vda+82L2sJ-M1pjgEfUQw50zHc-w@mail.gmail.com> (raw)
In-Reply-To: <CAJFAV8wDMD6NLuMKumkxjv_gm5u+OR1JjGfHk74HZRVy6oWg6Q@mail.gmail.com>
On Thu, Jun 16, 2022 at 4:38 PM David Marchand
<david.marchand@redhat.com> wrote:
>
> On Mon, May 16, 2022 at 1:16 PM <xuan.ding@intel.com> wrote:
> > +static __rte_always_inline uint16_t
> > +virtio_dev_tx_async_split(struct virtio_net *dev, struct vhost_virtqueue *vq,
> > + struct rte_mempool *mbuf_pool, struct rte_mbuf **pkts, uint16_t count,
> > + int16_t dma_id, uint16_t vchan_id, bool legacy_ol_flags)
> > +{
> > + static bool allocerr_warned;
> > + bool dropped = false;
> > + uint16_t free_entries;
> > + uint16_t pkt_idx, slot_idx = 0;
> > + uint16_t nr_done_pkts = 0;
> > + uint16_t pkt_err = 0;
> > + uint16_t n_xfer;
> > + struct vhost_async *async = vq->async;
> > + struct async_inflight_info *pkts_info = async->pkts_info;
> > + struct rte_mbuf *pkts_prealloc[MAX_PKT_BURST];
>
> Why do we need this array?
> Plus, see blow.
>
> > + uint16_t pkts_size = count;
> > +
> > + /**
> > + * The ordering between avail index and
> > + * desc reads needs to be enforced.
> > + */
> > + free_entries = __atomic_load_n(&vq->avail->idx, __ATOMIC_ACQUIRE) -
> > + vq->last_avail_idx;
> > + if (free_entries == 0)
> > + goto out;
> > +
> > + rte_prefetch0(&vq->avail->ring[vq->last_avail_idx & (vq->size - 1)]);
> > +
> > + async_iter_reset(async);
> > +
> > + count = RTE_MIN(count, MAX_PKT_BURST);
^^^
Ok, my point about the overflow does not stand.
Just the pkts_prealloc array is probably useless.
> > + count = RTE_MIN(count, free_entries);
> > + VHOST_LOG_DATA(DEBUG, "(%s) about to dequeue %u buffers\n",
> > + dev->ifname, count);
> > +
> > + if (rte_pktmbuf_alloc_bulk(mbuf_pool, pkts_prealloc, count))
>
> 'count' is provided by the user of the vhost async dequeue public API.
> There is no check that it is not bigger than MAX_PKT_BURST.
>
> Calling rte_pktmbuf_alloc_bulk on a fixed-size array pkts_prealloc,
> allocated on the stack, it may cause a stack overflow.
The rest still stands for me.
vvv
>
>
>
> This code is mostly copy/pasted from the "sync" code.
> I see a fix on the stats has been sent.
> I point here another bug.
> There are probably more...
>
> <grmbl>
> I don't like how async code has been added in the vhost library by Intel.
>
> Maxime did a cleanup on the enqueue patch
> https://patchwork.dpdk.org/project/dpdk/list/?series=20020&state=%2A&archive=both.
> I see that the recent dequeue path additions have the same method of
> copying/pasting code and adding some branches in a non systematic way.
> Please clean this code and stop copy/pasting without a valid reason.
> </grmbl>
--
David Marchand
next prev parent reply other threads:[~2022-06-16 14:40 UTC|newest]
Thread overview: 73+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-04-07 15:25 [PATCH v1 0/5] vhost: support async dequeue data path xuan.ding
2022-04-07 15:25 ` [PATCH v1 1/5] vhost: prepare sync for descriptor to mbuf refactoring xuan.ding
2022-04-07 15:25 ` [PATCH v1 2/5] vhost: prepare async " xuan.ding
2022-04-07 15:25 ` [PATCH v1 3/5] vhost: merge sync and async descriptor to mbuf filling xuan.ding
2022-04-07 15:25 ` [PATCH v1 4/5] vhost: support async dequeue for split ring xuan.ding
2022-04-07 15:25 ` [PATCH v1 5/5] examples/vhost: support async dequeue data path xuan.ding
2022-04-11 10:00 ` [PATCH v2 0/5] vhost: " xuan.ding
2022-04-11 10:00 ` [PATCH v2 1/5] vhost: prepare sync for descriptor to mbuf refactoring xuan.ding
2022-04-11 10:00 ` [PATCH v2 2/5] vhost: prepare async " xuan.ding
2022-04-11 10:00 ` [PATCH v2 3/5] vhost: merge sync and async descriptor to mbuf filling xuan.ding
2022-04-11 10:00 ` [PATCH v2 4/5] vhost: support async dequeue for split ring xuan.ding
2022-04-11 10:00 ` [PATCH v2 5/5] examples/vhost: support async dequeue data path xuan.ding
2022-04-19 3:43 ` [PATCH v3 0/5] vhost: " xuan.ding
2022-04-19 3:43 ` [PATCH v3 1/5] vhost: prepare sync for descriptor to mbuf refactoring xuan.ding
2022-04-22 15:30 ` Maxime Coquelin
2022-04-19 3:43 ` [PATCH v3 2/5] vhost: prepare async " xuan.ding
2022-04-22 15:32 ` Maxime Coquelin
2022-04-19 3:43 ` [PATCH v3 3/5] vhost: merge sync and async descriptor to mbuf filling xuan.ding
2022-04-22 11:06 ` David Marchand
2022-04-22 15:46 ` Maxime Coquelin
2022-04-24 2:02 ` Ding, Xuan
2022-04-22 15:43 ` Maxime Coquelin
2022-04-19 3:43 ` [PATCH v3 4/5] vhost: support async dequeue for split ring xuan.ding
2022-04-19 3:43 ` [PATCH v3 5/5] examples/vhost: support async dequeue data path xuan.ding
2022-05-05 6:23 ` [PATCH v4 0/5] vhost: " xuan.ding
2022-05-05 6:23 ` [PATCH v4 1/5] vhost: prepare sync for descriptor to mbuf refactoring xuan.ding
2022-05-05 7:37 ` Yang, YvonneX
2022-05-05 6:23 ` [PATCH v4 2/5] vhost: prepare async " xuan.ding
2022-05-05 7:38 ` Yang, YvonneX
2022-05-05 6:23 ` [PATCH v4 3/5] vhost: merge sync and async descriptor to mbuf filling xuan.ding
2022-05-05 7:39 ` Yang, YvonneX
2022-05-05 6:23 ` [PATCH v4 4/5] vhost: support async dequeue for split ring xuan.ding
2022-05-05 7:40 ` Yang, YvonneX
2022-05-05 19:36 ` Maxime Coquelin
2022-05-05 6:23 ` [PATCH v4 5/5] examples/vhost: support async dequeue data path xuan.ding
2022-05-05 7:39 ` Yang, YvonneX
2022-05-05 19:38 ` Maxime Coquelin
2022-05-05 19:52 ` [PATCH v4 0/5] vhost: " Maxime Coquelin
2022-05-06 1:49 ` Ding, Xuan
2022-05-13 2:00 ` [PATCH v5 " xuan.ding
2022-05-13 2:00 ` [PATCH v5 1/5] vhost: prepare sync for descriptor to mbuf refactoring xuan.ding
2022-05-13 2:00 ` [PATCH v5 2/5] vhost: prepare async " xuan.ding
2022-05-13 2:00 ` [PATCH v5 3/5] vhost: merge sync and async descriptor to mbuf filling xuan.ding
2022-05-13 2:00 ` [PATCH v5 4/5] vhost: support async dequeue for split ring xuan.ding
2022-05-13 2:24 ` Stephen Hemminger
2022-05-13 2:33 ` Ding, Xuan
2022-05-13 2:00 ` [PATCH v5 5/5] examples/vhost: support async dequeue data path xuan.ding
2022-05-13 2:50 ` [PATCH v6 0/5] vhost: " xuan.ding
2022-05-13 2:50 ` [PATCH v6 1/5] vhost: prepare sync for descriptor to mbuf refactoring xuan.ding
2022-05-13 2:50 ` [PATCH v6 2/5] vhost: prepare async " xuan.ding
2022-05-13 2:50 ` [PATCH v6 3/5] vhost: merge sync and async descriptor to mbuf filling xuan.ding
2022-05-13 2:50 ` [PATCH v6 4/5] vhost: support async dequeue for split ring xuan.ding
2022-05-13 2:50 ` [PATCH v6 5/5] examples/vhost: support async dequeue data path xuan.ding
2022-05-13 3:27 ` Xia, Chenbo
2022-05-13 3:51 ` Ding, Xuan
2022-05-16 2:43 ` [PATCH v7 0/5] vhost: " xuan.ding
2022-05-16 2:43 ` [PATCH v7 1/5] vhost: prepare sync for descriptor to mbuf refactoring xuan.ding
2022-05-16 2:43 ` [PATCH v7 2/5] vhost: prepare async " xuan.ding
2022-05-16 2:43 ` [PATCH v7 3/5] vhost: merge sync and async descriptor to mbuf filling xuan.ding
2022-05-16 2:43 ` [PATCH v7 4/5] vhost: support async dequeue for split ring xuan.ding
2022-05-16 5:52 ` Hu, Jiayu
2022-05-16 6:10 ` Ding, Xuan
2022-05-16 2:43 ` [PATCH v7 5/5] examples/vhost: support async dequeue data path xuan.ding
2022-05-16 11:10 ` [PATCH v8 0/5] vhost: " xuan.ding
2022-05-16 11:10 ` [PATCH v8 1/5] vhost: prepare sync for descriptor to mbuf refactoring xuan.ding
2022-05-16 11:10 ` [PATCH v8 2/5] vhost: prepare async " xuan.ding
2022-05-16 11:10 ` [PATCH v8 3/5] vhost: merge sync and async descriptor to mbuf filling xuan.ding
2022-05-16 11:10 ` [PATCH v8 4/5] vhost: support async dequeue for split ring xuan.ding
2022-06-16 14:38 ` David Marchand
2022-06-16 14:40 ` David Marchand [this message]
2022-06-17 6:34 ` Ding, Xuan
2022-05-16 11:10 ` [PATCH v8 5/5] examples/vhost: support async dequeue data path xuan.ding
2022-05-17 13:22 ` [PATCH v8 0/5] vhost: " Maxime Coquelin
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