netdev - Re: [PATCH net-next] cxgb4: Add low latency socket busy

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Message-ID: <1423036250.907.101.camel@edumazet-glaptop2.roam.corp.google.com>
Date:	Tue, 03 Feb 2015 23:50:50 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Kumar Sanghvi <kumaras@...lsio.com>
Cc:	Hariprasad Shenai <hariprasad@...lsio.com>, netdev@...r.kernel.org,
	davem@...emloft.net, leedom@...lsio.com, anish@...lsio.com,
	nirranjan@...lsio.com, praveenm@...lsio.com
Subject: Re: [PATCH net-next] cxgb4: Add low latency socket busy_poll support

On Wed, 2015-02-04 at 12:21 +0600, Kumar Sanghvi wrote:
> On Tuesday, February 02/03/15, 2015 at 21:58:29 -0800, Eric Dumazet wrote:
> > On Tue, 2015-02-03 at 10:50 +0530, Hariprasad Shenai wrote:
> > 
> > > @@ -1978,9 +2016,13 @@ static int napi_rx_handler(struct napi_struct *napi, int budget)
> > >  {
> > >  	unsigned int params;
> > >  	struct sge_rspq *q = container_of(napi, struct sge_rspq, napi);
> > > -	int work_done = process_responses(q, budget);
> > > +	int work_done = 0;
> > >  	u32 val;
> > >  
> > > +	if (!cxgb_poll_lock_napi(q))
> > > +		return work_done;
> > > +
> > 
> > 
> > This is very suspicious. Please take a look at commits
> > 
> > 24e579c8898aa641 ("bnx2x: fix napi poll return value for repoll") 
> > f104fedc0da126ab ("enic: fix rx napi poll return value")
> > 
> > for context.
> 
> Thanks Eric for pointing on this.
> So, this probably needs change after commit d75b1ade567ffab ("net: less interrupt masking in NAPI"), or
> is there something else that is missed ?

Right, you probably need to return budget here, not 0 (work_done == 0 at
this stage)



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