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Date: Mon, 11 Jun 2007 16:38:43 +0200 From: Patrick McHardy <kaber@...sh.net> To: "Cohen, Guy" <guy.cohen@...el.com> CC: hadi@...erus.ca, "Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>, davem@...emloft.net, netdev@...r.kernel.org, jeff@...zik.org, "Kok, Auke-jan H" <auke-jan.h.kok@...el.com> Subject: Re: [PATCH] NET: Multiqueue network device support. Cohen, Guy wrote: > Patrick McHardy wrote: > >>jamal wrote: >> >>>Sure - but what is wrong with that? >> >> >>Nothing, this was just to illustrate why I disagree with the > > assumption > >>that the packet has hit the wire. On second thought I do agree with > > your > >>assumption for the single HW queue case, at the point we hand the > > packet > >>to the HW the packet order is determined and is unchangeable. But this >>is not the case if the hardware includes its own scheduler. The qdisc >>is simply not fully in charge anymore. > > > For WiFi devices the HW often implements the scheduling, especially when > QoS (WMM/11e/11n) is implemented. There are few traffic queues defined > by the specs and the selection of the next queue to transmit a packet > from, is determined in real time, just when there is a tx opportunity. > This cannot be predicted in advance since it depends on the medium usage > of other stations. > > Hence, to make it possible for wireless devices to use the qdisc > mechanism properly, the HW queues should _ALL_ be non-empty at all > times, whenever data is available in the upper layers. Or in other > words, the upper layers should not block a specific queue because of the > usage of any other queue. Thats exactly what I'm saying. And its not possible with a single queue state as I tried to explain in my last last. - 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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