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Date: Sun, 1 Nov 2009 14:20:17 +0100 From: Jarek Poplawski <jarkao2@...il.com> To: Michael Chan <mchan@...adcom.com> Cc: Patrick McHardy <kaber@...sh.net>, Eric Dumazet <eric.dumazet@...il.com>, "David S. Miller" <davem@...emloft.net>, Linux Netdev List <netdev@...r.kernel.org> Subject: Re: [RFC] multiqueue changes On Sat, Oct 31, 2009 at 10:25:52AM -0700, Michael Chan wrote: > > On Fri, 2009-10-30 at 03:00 -0700, Jarek Poplawski wrote: > > On Thu, Oct 29, 2009 at 11:12:39PM +0100, Patrick McHardy wrote: ... > > > I currently can't see any purpose in decreasing num_tx_queues after > > > registration instead of real_num_tx_queues. > > > > I agree, but since Eric's example shows some drivers do it (almost) > > like this, I'd prefer authors/maintainers answer this question. > > > > We need the netdev and the private structure at the beginning of > ->probe() to store values as we probe the device. Later on in > ->probe(), we'll know whether the device supports MSI-X and multiqueue. > If we successfully enable MSI-X in ->ndo_open(), tx multiqueue will be > used. > > So if we can separate the allocation of the netdev and the private > structure from the tx queues, we can allocate and set the exact number > of num_tx_queues in ->ndo_open(). There is a question if we can predict in ->probe() MSI-X should be successfully enabled in ->ndo_open() for probed hardware. If so, then it could go e.g. like this: ->probe() ... dev = alloc_etherdev_mq(sizeof(*bp), 1) ... if (MSI-X_available && device_supports_MSI-X_and_multiqueue) realloc_netdev_mq(dev, TX_MAX_RINGS) register_netdev(dev) ->ndo_open() if (!enabled_MSI-X) /* something gone wrong but it's an exception */ dev->real_num_tx_queues = 1 Otherwise, (re)allocation in ->ndo_open() would need to answer some questions about reinitializing scheduler vs preserving qdisc stats between opens. Jarek P. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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