RE: [PATCH net v2] igb: fix netpoll exit with traffic

From: Danielle Ratson <danieller@nvidia.com>
To: Jesse Brandeburg <jesse.brandeburg@intel.com>,
	"intel-wired-lan@lists.osuosl.org"
	<intel-wired-lan@lists.osuosl.org>
Cc: "netdev@vger.kernel.org" <netdev@vger.kernel.org>,
	Oleksandr Natalenko <oleksandr@natalenko.name>,
	Alexander Duyck <alexander.duyck@gmail.com>
Subject: RE: [PATCH net v2] igb: fix netpoll exit with traffic
Date: Thu, 25 Nov 2021 08:01:40 +0000	[thread overview]
Message-ID: <DM6PR12MB4516B65E19B294524570296FD8629@DM6PR12MB4516.namprd12.prod.outlook.com> (raw)
In-Reply-To: <DM6PR12MB451662EC02B77D17A9C27473D8629@DM6PR12MB4516.namprd12.prod.outlook.com>


> -----Original Message-----
> From: Danielle Ratson
> Sent: Thursday, November 25, 2021 9:37 AM
> To: Jesse Brandeburg <jesse.brandeburg@intel.com>; intel-wired-
> lan@lists.osuosl.org
> Cc: netdev@vger.kernel.org; Oleksandr Natalenko
> <oleksandr@natalenko.name>; Alexander Duyck
> <alexander.duyck@gmail.com>
> Subject: RE: [PATCH net v2] igb: fix netpoll exit with traffic
> 
> 
> 
> > -----Original Message-----
> > From: Jesse Brandeburg <jesse.brandeburg@intel.com>
> > Sent: Tuesday, November 23, 2021 10:40 PM
> > To: intel-wired-lan@lists.osuosl.org
> > Cc: Jesse Brandeburg <jesse.brandeburg@intel.com>;
> > netdev@vger.kernel.org; Oleksandr Natalenko
> > <oleksandr@natalenko.name>; Danielle Ratson <danieller@nvidia.com>;
> > Alexander Duyck <alexander.duyck@gmail.com>
> > Subject: [PATCH net v2] igb: fix netpoll exit with traffic
> >
> > Oleksandr brought a bug report where netpoll causes trace messages in
> > the log on igb.
> >
> > Danielle brought this back up as still occuring, so we'll try again.
> >
> > [22038.710800] ------------[ cut here ]------------ [22038.710801]
> > igb_poll+0x0/0x1440 [igb] exceeded budget in poll [22038.710802]
> > WARNING: CPU: 12 PID: 40362 at net/core/netpoll.c:155
> > netpoll_poll_dev+0x18a/0x1a0
> >
> > As Alex suggested, change the driver to return work_done at the exit
> > of napi_poll, which should be safe to do in this driver because it is
> > not polling multiple queues in this single napi context (multiple
> > queues attached to one MSI-X vector). Several other drivers contain
> > the same simple sequence, so I hope this will not create new problems.
> >
> > Fixes: 16eb8815c235 ("igb: Refactor clean_rx_irq to reduce overhead
> > and improve performance")
> > Reported-by: Oleksandr Natalenko <oleksandr@natalenko.name>
> > Reported-by: Danielle Ratson <danieller@nvidia.com>
> > Suggested-by: Alexander Duyck <alexander.duyck@gmail.com>
> > Signed-off-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
> > ---
> > COMPILE TESTED ONLY! I have no way to reproduce this even on a machine
> > I have with igb. It works fine to load the igb driver and netconsole
> > with no errors.
> > ---
> > v2: simplified patch with an attempt to make it work
> > v1: original patch that apparently didn't work
> > ---
> >  drivers/net/ethernet/intel/igb/igb_main.c | 2 +-
> >  1 file changed, 1 insertion(+), 1 deletion(-)
> >
> > diff --git a/drivers/net/ethernet/intel/igb/igb_main.c
> > b/drivers/net/ethernet/intel/igb/igb_main.c
> > index e647cc89c239..5e24b7ce5a92 100644
> > --- a/drivers/net/ethernet/intel/igb/igb_main.c
> > +++ b/drivers/net/ethernet/intel/igb/igb_main.c
> > @@ -8104,7 +8104,7 @@ static int igb_poll(struct napi_struct *napi,
> > int
> > budget)
> >  	if (likely(napi_complete_done(napi, work_done)))
> >  		igb_ring_irq_enable(q_vector);
> >
> > -	return min(work_done, budget - 1);
> > +	return work_done;
> >  }
> >
> >  /**
> > --
> > 2.33.1
> 
> Tested and looks ok, thanks!

Tested-By: Danielle Ratson <danieller@nvidia.com>