netdev - RE: [PATCH] NET: Multiqueue network device support.

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Date:	Mon, 11 Jun 2007 10:48:05 -0400
From:	jamal <hadi@...erus.ca>
To:	"Cohen, Guy" <guy.cohen@...el.com>
Cc:	Patrick McHardy <kaber@...sh.net>,
	"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.

On Mon, 2007-11-06 at 17:30 +0300, Cohen, Guy wrote:

> 
> 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.

WMM is a strict prio mechanism.
The parametrization very much favors the high prio packets when the
tx opportunity to send shows up.

> 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. 

agreed.

> Or in other
> words, the upper layers should not block a specific queue because of the
> usage of any other queue.

This is where we are going to disagree. 
There is no way the stack will send the driver packets which are low
prio if there are some which are high prio. There is therefore, on
contention between low and high prio, no way for low prio packets to
obstruct the high prio packets; however, it is feasible that high prio
packets will obstruct low prio packets (which is fine). 

cheers,
jamal

-
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