Messages in this thread | | | Subject | Re: [PATCH] virtio-net: parameterize min ring num_free for virtio receive | From | Jason Wang <> | Date | Thu, 18 Jul 2019 22:01:05 +0800 |
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On 2019/7/18 下午9:04, Michael S. Tsirkin wrote: > On Thu, Jul 18, 2019 at 12:55:50PM +0000, ? jiang wrote: >> This change makes ring buffer reclaim threshold num_free configurable >> for better performance, while it's hard coded as 1/2 * queue now. >> According to our test with qemu + dpdk, packet dropping happens when >> the guest is not able to provide free buffer in avail ring timely. >> Smaller value of num_free does decrease the number of packet dropping >> during our test as it makes virtio_net reclaim buffer earlier. >> >> At least, we should leave the value changeable to user while the >> default value as 1/2 * queue is kept. >> >> Signed-off-by: jiangkidd<jiangkidd@hotmail.com> > That would be one reason, but I suspect it's not the > true one. If you need more buffer due to jitter > then just increase the queue size. Would be cleaner. > > > However are you sure this is the reason for > packet drops? Do you see them dropped by dpdk > due to lack of space in the ring? As opposed to > by guest? > >
Besides those, this patch depends on the user to choose a suitable threshold which is not good. You need either a good value with demonstrated numbers or something smarter.
Thanks
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