netdev - Re: [RFC PATCH] Regression in linux 2.6.32 virtio

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Message-ID: <OF3CFC3E46.A2924517-ON6525768F.00461897-6525768F.0046CFE9@in.ibm.com>
Date:	Thu, 17 Dec 2009 18:34:40 +0530
From:	Krishna Kumar2 <krkumar2@...ibm.com>
To:	Jarek Poplawski <jarkao2@...il.com>
Cc:	"David S. Miller" <davem@...emloft.net>,
	Herbert Xu <herbert@...dor.apana.org.au>, mst@...hat.com,
	netdev@...r.kernel.org, Rusty Russell <rusty@...tcorp.com.au>,
	Sridhar Samudrala <sri@...ibm.com>
Subject: Re: [RFC PATCH] Regression in linux 2.6.32 virtio_net seen with	vhost-net

Jarek Poplawski <jarkao2@...il.com> wrote on 12/17/2009 06:12:54 PM:
>
> On Thu, Dec 17, 2009 at 05:57:15PM +0530, Krishna Kumar2 wrote:
> > the first resched. I also think the resched in requeue is probably
> > not required, since the device will call netif_tx_wake_queue anyway.
>
> IIRC there were mentioned some possibly broken drivers around these
> changes. So it would require a little bit of reviewing...

Yes, that was the reason I dropped that patch before submitting. I
was not sure of that optimization since I didn't check that all,
esp antique drivers, would resched correctly, but that was only a
minor optimization (avoiding one call of resched per stop).

However, the qdisc_restart/dev_dequeue path is clean since the stopped
txq case is handled very early, and no actual dequeue/requeue/resched
happens till the device restarts the txq.

Thanks,

- KK

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