netdev - RE: [PATCH 1/4] [NET_SCHED] explict hold dev tx lock

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Date:	Mon, 24 Sep 2007 18:51:38 -0400
From:	jamal <hadi@...erus.ca>
To:	"Waskiewicz Jr, Peter P" <peter.p.waskiewicz.jr@...el.com>
Cc:	David Miller <davem@...emloft.net>, krkumar2@...ibm.com,
	johnpol@....mipt.ru, herbert@...dor.apana.org.au, kaber@...sh.net,
	shemminger@...ux-foundation.org, jagana@...ibm.com,
	Robert.Olsson@...a.slu.se, rick.jones2@...com, xma@...ibm.com,
	gaagaan@...il.com, netdev@...r.kernel.org, rdreier@...co.com,
	mcarlson@...adcom.com, jeff@...zik.org, mchan@...adcom.com,
	general@...ts.openfabrics.org, kumarkr@...ux.ibm.com,
	tgraf@...g.ch, randy.dunlap@...cle.com, sri@...ibm.com
Subject: RE: [PATCH 1/4] [NET_SCHED] explict hold dev tx lock

On Mon, 2007-24-09 at 12:12 -0700, Waskiewicz Jr, Peter P wrote:

> Hi Jamal,
> 	I've been (slowly) working on resurrecting the original design
> of my multiqueue patches to address this exact issue of the queue_lock
> being a hot item.  I added a queue_lock to each queue in the subqueue
> struct, and in the enqueue and dequeue, just lock that queue instead of
> the global device queue_lock.  The only two issues to overcome are the
> QDISC_RUNNING state flag, since that also serializes entry into the
> qdisc_restart() function, and the qdisc statistics maintenance, which
> needs to be serialized.  Do you think this work along with your patch
> will benefit from one another? 

The one thing that seems obvious is to use dev->hard_prep_xmit() in the
patches i posted to select the xmit ring. You should be able to do
figure out the txmit ring without holding any lock. 

I lost track of how/where things went since the last discussion; so i
need to wrap my mind around it to make sensisble suggestions - I know
the core patches are in the kernel but havent paid attention to details
and if you look at my second patch youd see a comment in
dev_batch_xmit() which says i need to scrutinize multiqueue more. 

cheers,
jamal

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