netdev - Re: NAPI rescheduling and the delay caused by it

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Message-ID: <52A8B465.60304@citrix.com>
Date:	Wed, 11 Dec 2013 18:52:21 +0000
From:	Zoltan Kiss <zoltan.kiss@...rix.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	"netdev@...r.kernel.org" <netdev@...r.kernel.org>,
	"xen-devel@...ts.xenproject.org" <xen-devel@...ts.xenproject.org>,
	Malcolm Crossley <malcolm.crossley@...rix.com>,
	Jonathan Davies <Jonathan.Davies@...rix.com>,
	Paul Durrant <Paul.Durrant@...rix.com>,
	Wei Liu <wei.liu2@...rix.com>,
	Ian Campbell <Ian.Campbell@...rix.com>
Subject: Re: NAPI rescheduling and the delay caused by it

On 10/12/13 01:14, Eric Dumazet wrote:
> On Mon, 2013-12-09 at 23:39 +0000, Zoltan Kiss wrote:
>> I found another suspect however: my grant mapping patches do the
>> unmapping from the NAPI instance where otherwise we receive the
>> packets from the guest. But this means we call napi_schedule from the
>> zerocopy callback, which can be run by anyone who free up that skb,
>> including an another VIF's RX thread (which actually does the transmit
>> TO the guest). I guess that might be bad.
>
> Same problem : napi_schedule() is meant to be used from interrupt
> context.

Indeed, avoiding napi_schedule seems to solve the issue. Thanks for the 
advices!

Zoli
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