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From: Jason Wang <jasowang@redhat.com>
To: "Michael S. Tsirkin" <mst@redhat.com>
Cc: virtualization@lists.linux-foundation.org,
	netdev@vger.kernel.org, linux-kernel@vger.kernel.org,
	bpf@vger.kernel.org, Jesper Dangaard Brouer <brouer@redhat.com>,
	Eugenio Perez Martin <eperezma@redhat.com>
Subject: Re: performance bug in virtio net xdp
Date: Wed, 6 May 2020 16:37:41 +0800	[thread overview]
Message-ID: <7d801479-5572-0031-b306-a735ca4ce0e4@redhat.com> (raw)
In-Reply-To: <20200506035704-mutt-send-email-mst@kernel.org>


On 2020/5/6 下午4:08, 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.
>


  reply	other threads:[~2020-05-06  8:37 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-05-06  8:08 Michael S. Tsirkin
2020-05-06  8:37 ` Jason Wang [this message]
2020-05-06 11:57   ` Michael S. Tsirkin
2020-05-06  8:37 ` Jesper Dangaard Brouer
2020-05-06 11:57   ` Michael S. Tsirkin

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