Re: [PATCH v6 8/9] net/mlx5: Do not call pcie_print_link_status()

[Alex G.]

On 08/08/2018 10:56 AM, Tal Gilboa wrote:
> On 8/8/2018 6:41 PM, Leon Romanovsky wrote:
> > On Wed, Aug 08, 2018 at 05:23:12PM +0300, Tal Gilboa wrote:
> > > On 8/8/2018 9:08 AM, Leon Romanovsky wrote:
> > > > On Mon, Aug 06, 2018 at 06:25:42PM -0500, Alexandru Gagniuc wrote:
> > > > > This is now done by the PCI core to warn of sub-optimal bandwidth.
> > > > >
> > > > > Signed-off-by: Alexandru Gagniuc <mr.nuke.me@xxxxxxxxx>
> > > > > ---
> > > > >    drivers/net/ethernet/mellanox/mlx5/core/main.c | 4 ----
> > > > >    1 file changed, 4 deletions(-)
> > > >
> > > > Thanks,
> > > > Reviewed-by: Leon Romanovsky <leonro@xxxxxxxxxxxx>
> > >
> > > Alex,
> > > I loaded mlx5 driver with and without these series. The report in 
> > > dmesg is
> > > now missing. From what I understood, the status should be reported at 
> > > least
> > > once, even if everything is in order.
> >
> > It is not what this series is doing and it removes prints completely if
> > fabric can deliver more than card is capable.
> >
> > > We need this functionality to stay.
> >
> > I'm not sure that you need this information in driver's dmesg output,
> > but most probably something globally visible and accessible per-pci
> > device.
>
> Currently we have users that look for it. If we remove the dmesg print 
> we need this to be reported elsewhere. Adding it to sysfs for example 
> should be a valid solution for our case.

I think a stop-gap measure is to leave the pcie_print_link_status() call 
in drivers that really need it for whatever reason. Implementing a 
reliable reporting through sysfs might take some tinkering, and I don't 
think it's a sufficient reason to block the heart of this series -- 
being able to detect bottlenecks and link downtraining.

Alex

> > > net-next (dmesg output for 07:00.0):
> > > [270498.625351] mlx5_core 0000:07:00.0: firmware version: 14.22.4020
> > > [270498.632130] mlx5_core 0000:07:00.0: 63.008 Gb/s available PCIe 
> > > bandwidth
> > > (8 GT/s x8 link)
> > > [270499.169533] (0000:07:00.0): E-Switch: Total vports 9, per vport: max
> > > uc(1024) max mc(16384)
> > > [270499.182358] mlx5_core 0000:07:00.0: Port module event: module 0, 
> > > Cable
> > > plugged
> > >
> > > net-next + patches (dmesg output for 07:00.0):
> > > [  331.608472] mlx5_core 0000:07:00.0: firmware version: 14.22.4020
> > > [  332.564938] (0000:07:00.0): E-Switch: Total vports 9, per vport: max
> > > uc(1024) max mc(16384)
> > > [  332.616271] mlx5_core 0000:07:00.0: Port module event: module 0, 
> > > Cable
> > > plugged