netdev - Re: [PATCH net-next] net: allow large number of tx queues

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Date:	Fri, 21 Jun 2013 00:12:30 -0700
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Jason Wang <jasowang@...hat.com>
Cc:	"Michael S. Tsirkin" <mst@...hat.com>, davem@...emloft.net,
	hkchu@...gle.com, netdev <netdev@...r.kernel.org>,
	dwmw2@...radead.org
Subject: Re: [PATCH net-next] net: allow large number of tx queues

On Fri, 2013-06-21 at 14:41 +0800, Jason Wang wrote:

> 1K queues (about 80 pages) looks a little bit aggressive which means we
> may always fall back to vmalloc()?

1K queues looks like you should use 0 queue (LLTX) in fact, so that you
design the minimal percpu structure in the driver to fit the needs.

Using Qdisc, qith MQ, pfifo_fast, on 1000 'queues' is adding a fair
amount of overhead and memory usage.

For example, loopback driver only needs small percpu structure (16
bytes), as it immediately forward the packet into netif_rx() [ Which
also use a percpu area called softnet_data ]



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