Messages in this thread | | | Subject | Re: [PATCH v2 1/8] vsock/virtio: limit the memory used per-socket | From | Jason Wang <> | Date | Wed, 29 May 2019 08:59:03 +0800 |
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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
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