netdev - Re: [PATCH net-next 4/4] virtio-net: auto-tune mergeable rx buffer size for improved performance

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Date:	Wed, 13 Nov 2013 06:19:08 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Ronen Hod <rhod@...hat.com>
Cc:	Michael Dalton <mwdalton@...gle.com>,
	"David S. Miller" <davem@...emloft.net>, netdev@...r.kernel.org,
	Eric Dumazet <edumazet@...gle.com>,
	Rusty Russell <rusty@...tcorp.com.au>,
	"Michael S. Tsirkin" <mst@...hat.com>,
	Daniel Borkmann <dborkman@...hat.com>,
	Jason Wang <jasowang@...hat.com>,
	Eric Northup <digitaleric@...gle.com>,
	virtualization@...ts.linux-foundation.org
Subject: Re: [PATCH net-next 4/4] virtio-net: auto-tune mergeable rx buffer
 size for improved performance

On Wed, 2013-11-13 at 10:47 +0200, Ronen Hod wrote:

> I looked at how ewma works, and although it is computationally efficient,
> and it does what it is supposed to do, initially (at the first samples) it is strongly
> biased towards the value that was added at the first ewma_add.
> I suggest that you print the values of ewma_add() and ewma_read(). If you are
> happy with the results, then ignore my comments. If you are not, then I can
> provide a version that does better for the first samples.
> Unfortunately, it will be slightly less efficient.

Value is clamped by (GOOD_PACKET_LEN, PAGE_SIZE - hdr_len)

So initial value is conservative and not really used.

Thanks


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