netdev - Re: [PATCH v6 8/9] net/mlx5: Do not call pcie_print_link

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Date:   Wed, 8 Aug 2018 20:27:36 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     "Alex G." <mr.nuke.me@...il.com>
Cc:     Tal Gilboa <talgi@...lanox.com>, linux-pci@...r.kernel.org,
        bhelgaas@...gle.com, jakub.kicinski@...ronome.com,
        keith.busch@...el.com, alex_gagniuc@...lteam.com,
        austin_bolen@...l.com, shyam_iyer@...l.com,
        Ariel Elior <ariel.elior@...ium.com>,
        everest-linux-l2@...ium.com,
        "David S. Miller" <davem@...emloft.net>,
        Michael Chan <michael.chan@...adcom.com>,
        Ganesh Goudar <ganeshgr@...lsio.com>,
        Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
        Tariq Toukan <tariqt@...lanox.com>,
        Saeed Mahameed <saeedm@...lanox.com>,
        Dirk van der Merwe <dirk.vandermerwe@...ronome.com>,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
        intel-wired-lan@...ts.osuosl.org, linux-rdma@...r.kernel.org,
        oss-drivers@...ronome.com
Subject: Re: [PATCH v6 8/9] net/mlx5: Do not call pcie_print_link_status()

On Wed, Aug 08, 2018 at 11:33:51AM -0500, Alex G. wrote:
>
>
> 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@...il.com>
> > > > > > ---
> > > > > >    drivers/net/ethernet/mellanox/mlx5/core/main.c | 4 ----
> > > > > >    1 file changed, 4 deletions(-)
> > > > > >
> > > > >
> > > > > Thanks,
> > > > > Reviewed-by: Leon Romanovsky <leonro@...lanox.com>
> > > > >
> > > >
> > > > 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.

IMHO, you did right change and it is better to replace this print to some
more generic solution now while you are doing it and don't leave leftovers.

Thanks

>
> 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
> > > >
> > > >

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