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Message-ID: <5432B6D2.9030503@oracle.com>
Date: Mon, 06 Oct 2014 11:35:46 -0400
From: annie li <annie.li@...cle.com>
To: David Vrabel <david.vrabel@...rix.com>
CC: netdev@...r.kernel.org, xen-devel@...ts.xenproject.org,
Boris Ostrovsky <boris.ostrovsky@...cle.com>
Subject: Re: [Xen-devel] [PATCHv1] xen-netfront: always keep the Rx ring full
of requests
On 2014/10/2 9:33, David Vrabel wrote:
> A full Rx ring only requires 1 MiB of memory. This is not enough
> memory that it is useful to dynamically scale the number of Rx
> requests in the ring based on traffic rates.
>
> Keeping the ring full of Rx requests handles bursty traffic better
> than trying to converges on an optimal number of requests to keep
> filled.
>
> On a 4 core host, an iperf -P 64 -t 60 run from dom0 to a 4 VCPU guest
> improved from 5.1 Gbit/s to 5.6 Gbit/s. Gains with more bursty
> traffic are expected to be higher.
Although removing sysfs is connected with the code change for full Rx
ring utilization, I assume it is better to split this patch into two to
make it simpler?
...snip...
>
> + queue->rx.req_prod_pvt = req_prod;
> +
> + /* Not enough requests? Try again later. */
> + if (req_prod - queue->rx.rsp_cons < NET_RX_SLOTS_MIN) {
> + mod_timer(&queue->rx_refill_timer, jiffies + (HZ/10));
> + return;
If the previous for loop breaks because of failure of
xennet_alloc_one_rx_buffer, then notify_remote_via_irq is missed here if
the code returns directly.
Thanks
Annie
> + }
> +
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