From: Jason Wang <jasowang@redhat.com>
To: Stefano Garzarella <sgarzare@redhat.com>,
Stefan Hajnoczi <stefanha@redhat.com>
Cc: netdev@vger.kernel.org, "David S. Miller" <davem@davemloft.net>,
"Michael S. Tsirkin" <mst@redhat.com>,
virtualization@lists.linux-foundation.org,
linux-kernel@vger.kernel.org, kvm@vger.kernel.org
Subject: Re: [PATCH v2 1/8] vsock/virtio: limit the memory used per-socket
Date: Wed, 29 May 2019 08:59:03 +0800 [thread overview]
Message-ID: <3f0019cc-29b5-1ddd-fbcf-d5f1716ca802@redhat.com> (raw)
In-Reply-To: <20190528164521.k2euedfcmtvvynew@steredhat.homenet.telecomitalia.it>
On 2019/5/29 上午12:45, Stefano Garzarella wrote:
> On Wed, May 15, 2019 at 10:48:44AM +0800, Jason Wang wrote:
>> On 2019/5/15 上午12:35, Stefano Garzarella wrote:
>>> On Tue, May 14, 2019 at 11:25:34AM +0800, Jason Wang wrote:
>>>> On 2019/5/14 上午1:23, Stefano Garzarella wrote:
>>>>> On Mon, May 13, 2019 at 05:58:53PM +0800, Jason Wang wrote:
>>>>>> On 2019/5/10 下午8:58, Stefano Garzarella wrote:
>>>>>>> +static struct virtio_vsock_buf *
>>>>>>> +virtio_transport_alloc_buf(struct virtio_vsock_pkt *pkt, bool zero_copy)
>>>>>>> +{
>>>>>>> + struct virtio_vsock_buf *buf;
>>>>>>> +
>>>>>>> + if (pkt->len == 0)
>>>>>>> + return NULL;
>>>>>>> +
>>>>>>> + buf = kzalloc(sizeof(*buf), GFP_KERNEL);
>>>>>>> + if (!buf)
>>>>>>> + return NULL;
>>>>>>> +
>>>>>>> + /* If the buffer in the virtio_vsock_pkt is full, we can move it to
>>>>>>> + * the new virtio_vsock_buf avoiding the copy, because we are sure that
>>>>>>> + * we are not use more memory than that counted by the credit mechanism.
>>>>>>> + */
>>>>>>> + if (zero_copy && pkt->len == pkt->buf_len) {
>>>>>>> + buf->addr = pkt->buf;
>>>>>>> + pkt->buf = NULL;
>>>>>>> + } else {
>>>>>> Is the copy still needed if we're just few bytes less? We meet similar issue
>>>>>> for virito-net, and virtio-net solve this by always copy first 128bytes for
>>>>>> big packets.
>>>>>>
>>>>>> See receive_big()
>>>>> I'm seeing, It is more sophisticated.
>>>>> IIUC, virtio-net allocates a sk_buff with 128 bytes of buffer, then copies the
>>>>> first 128 bytes, then adds the buffer used to receive the packet as a frag to
>>>>> the skb.
>>>> Yes and the point is if the packet is smaller than 128 bytes the pages will
>>>> be recycled.
>>>>
>>>>
>>> So it's avoid the overhead of allocation of a large buffer. I got it.
>>>
>>> Just a curiosity, why the threshold is 128 bytes?
>>
>> From its name (GOOD_COPY_LEN), I think it just a value that won't lose much
>> performance, e.g the size two cachelines.
>>
> Jason, Stefan,
> since I'm removing the patches to increase the buffers to 64 KiB and I'm
> adding a threshold for small packets, I would simplify this patch,
> removing the new buffer allocation and copying small packets into the
> buffers already queued (if there is a space).
> In this way, I should solve the issue of 1 byte packets.
>
> Do you think could be better?
I think so.
Thanks
>
> Thanks,
> Stefano
next prev parent reply other threads:[~2019-05-29 0:59 UTC|newest]
Thread overview: 38+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-05-10 12:58 [PATCH v2 0/8] vsock/virtio: optimizations to increase the throughput Stefano Garzarella
2019-05-10 12:58 ` [PATCH v2 1/8] vsock/virtio: limit the memory used per-socket Stefano Garzarella
2019-05-12 16:57 ` Michael S. Tsirkin
2019-05-13 16:40 ` Stefano Garzarella
2019-05-13 9:58 ` Jason Wang
2019-05-13 17:23 ` Stefano Garzarella
2019-05-14 3:25 ` Jason Wang
2019-05-14 3:40 ` Jason Wang
2019-05-14 16:35 ` Stefano Garzarella
2019-05-15 2:48 ` Jason Wang
2019-05-28 16:45 ` Stefano Garzarella
2019-05-29 0:59 ` Jason Wang [this message]
2019-05-16 15:25 ` Stefan Hajnoczi
2019-05-17 8:25 ` Stefano Garzarella
2019-05-20 8:57 ` Stefan Hajnoczi
2019-05-10 12:58 ` [PATCH v2 2/8] vsock/virtio: free packets during the socket release Stefano Garzarella
2019-05-10 22:20 ` David Miller
2019-05-11 8:27 ` Stefano Garzarella
2019-05-16 15:32 ` Stefan Hajnoczi
2019-05-17 8:26 ` Stefano Garzarella
2019-05-10 12:58 ` [PATCH v2 3/8] vsock/virtio: fix locking for fwd_cnt and buf_alloc Stefano Garzarella
2019-05-10 12:58 ` [PATCH v2 4/8] vsock/virtio: reduce credit update messages Stefano Garzarella
2019-05-10 12:58 ` [PATCH v2 5/8] vhost/vsock: split packets to send using multiple buffers Stefano Garzarella
2019-05-10 12:58 ` [PATCH v2 6/8] vsock/virtio: change the maximum packet size allowed Stefano Garzarella
2019-05-10 12:58 ` [PATCH v2 7/8] vsock/virtio: increase RX buffer size to 64 KiB Stefano Garzarella
2019-05-13 10:01 ` Jason Wang
2019-05-13 17:51 ` Stefano Garzarella
2019-05-14 3:38 ` Jason Wang
2019-05-14 16:20 ` Stefano Garzarella
2019-05-15 2:50 ` Jason Wang
2019-05-15 8:22 ` Stefano Garzarella
2019-05-10 12:58 ` [PATCH v2 8/8] vsock/virtio: make the RX buffer size tunable Stefano Garzarella
2019-05-13 10:05 ` Jason Wang
2019-05-13 12:46 ` Jason Wang
2019-05-14 16:10 ` Stefano Garzarella
2019-05-13 9:33 ` [PATCH v2 0/8] vsock/virtio: optimizations to increase the throughput Jason Wang
2019-05-13 16:49 ` Stefano Garzarella
2019-05-20 14:09 ` Stefano Garzarella
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