Re: performance bug in virtio net xdp

[Jason Wang]

On 2020/5/6 äå4:08, Michael S. Tsirkin wrote:
> So for mergeable bufs, we use ewma machinery to guess the correct buffer
> size. If we don't guess correctly, XDP has to do aggressive copies.
>
> Problem is, xdp paths do not update the ewma at all, except
> sometimes with XDP_PASS. So whatever we happen to have
> before we attach XDP, will mostly stay around.


It looks ok to me since we always use PAGE_SIZE when XDP is enabled in 
get_mergeable_buf_len()?

Thanks


> The fix is probably to update ewma unconditionally.