From: Tal Gilboa <talgi@mellanox.com>
To: "Alex G." <mr.nuke.me@gmail.com>,
Jakub Kicinski <jakub.kicinski@netronome.com>
Cc: "linux-pci@vger.kernel.org" <linux-pci@vger.kernel.org>,
"bhelgaas@google.com" <bhelgaas@google.com>,
"keith.busch@intel.com" <keith.busch@intel.com>,
"alex_gagniuc@dellteam.com" <alex_gagniuc@dellteam.com>,
"austin_bolen@dell.com" <austin_bolen@dell.com>,
"shyam_iyer@dell.com" <shyam_iyer@dell.com>,
"jeffrey.t.kirsher@intel.com" <jeffrey.t.kirsher@intel.com>,
"ariel.elior@cavium.com" <ariel.elior@cavium.com>,
"michael.chan@broadcom.com" <michael.chan@broadcom.com>,
"ganeshgr@chelsio.com" <ganeshgr@chelsio.com>,
Tariq Toukan <tariqt@mellanox.com>,
"airlied@gmail.com" <airlied@gmail.com>,
"alexander.deucher@amd.com" <alexander.deucher@amd.com>,
"mike.marciniszyn@intel.com" <mike.marciniszyn@intel.com>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH v5] PCI: Check for PCIe downtraining conditions
Date: Tue, 24 Jul 2018 16:39:29 +0300 [thread overview]
Message-ID: <cf663b45-a6ce-b0d7-c79a-a02940001c20@mellanox.com> (raw)
In-Reply-To: <2bb6e96c-a48d-62ea-90a3-ec978536372f@gmail.com>
On 7/24/2018 2:59 AM, Alex G. wrote:
>
>
> On 07/23/2018 05:14 PM, Jakub Kicinski wrote:
>> On Tue, 24 Jul 2018 00:52:22 +0300, Tal Gilboa wrote:
>>> On 7/24/2018 12:01 AM, Jakub Kicinski wrote:
>>>> On Mon, 23 Jul 2018 15:03:38 -0500, Alexandru Gagniuc wrote:
>>>>> PCIe downtraining happens when both the device and PCIe port are
>>>>> capable of a larger bus width or higher speed than negotiated.
>>>>> Downtraining might be indicative of other problems in the system, and
>>>>> identifying this from userspace is neither intuitive, nor
>>>>> straightforward.
>>>>>
>>>>> The easiest way to detect this is with pcie_print_link_status(),
>>>>> since the bottleneck is usually the link that is downtrained. It's not
>>>>> a perfect solution, but it works extremely well in most cases.
>>>>>
>>>>> Signed-off-by: Alexandru Gagniuc <mr.nuke.me@gmail.com>
>>>>> ---
>>>>>
>>>>> For the sake of review, I've created a __pcie_print_link_status()
>>>>> which
>>>>> takes a 'verbose' argument. If we agree want to go this route, and
>>>>> update
>>>>> the users of pcie_print_link_status(), I can split this up in two
>>>>> patches.
>>>>> I prefer just printing this information in the core functions, and
>>>>> letting
>>>>> drivers not have to worry about this. Though there seems to be
>>>>> strong for
>>>>> not going that route, so here it goes:
>>>>
>>>> FWIW the networking drivers print PCIe BW because sometimes the network
>>>> bandwidth is simply over-provisioned on multi port cards, e.g. 80Gbps
>>>> card on a x8 link.
>>>>
>>>> Sorry to bike shed, but currently the networking cards print the info
>>>> during probe. Would it make sense to move your message closer to probe
>>>> time? Rather than when device is added. If driver structure is
>>>> available, we could also consider adding a boolean to struct pci_driver
>>>> to indicate if driver wants the verbose message? This way we avoid
>>>> duplicated prints.
>>>>
>>>> I have no objection to current patch, it LGTM. Just a thought.
>>>
>>> I don't see the reason for having two functions. What's the problem with
>>> adding the verbose argument to the original function?
>>
>> IMHO it's reasonable to keep the default parameter to what 90% of users
>> want by a means on a wrapper. The non-verbose output is provided by
>> the core already for all devices.
>>
>> What do you think of my proposal above Tal? That would make the extra
>> wrapper unnecessary since the verbose parameter would be part of the
>> driver structure, and it would avoid the duplicated output.
>
> I see how it might make sense to add another member to the driver
> struct, but is it worth the extra learning curve? It seems to be
> something with the potential to confuse new driver developers, and
> having a very marginal benefit.
> Although, if that's what people want...
I prefer the wrapper function. Looking at struct pci_driver it would
seem strange for it to hold a field for controlling verbosity (IMO).
This is a very (very) specific field in a very general struct.
>
> Alex
next prev parent reply other threads:[~2018-07-24 13:39 UTC|newest]
Thread overview: 47+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-06-04 15:55 [PATCH v3] PCI: Check for PCIe downtraining conditions Alexandru Gagniuc
2018-06-05 12:27 ` Andy Shevchenko
2018-06-05 13:04 ` Andy Shevchenko
2018-07-16 21:17 ` Bjorn Helgaas
2018-07-16 22:28 ` Alex_Gagniuc
2018-07-18 21:53 ` Bjorn Helgaas
2018-07-19 15:46 ` Alex G.
2018-07-23 20:01 ` [PATCH v2] PCI/AER: Do not clear AER bits if we don't own AER Alexandru Gagniuc
2018-07-25 1:24 ` kbuild test robot
2018-07-23 20:03 ` [PATCH v5] PCI: Check for PCIe downtraining conditions Alexandru Gagniuc
2018-07-23 21:01 ` Jakub Kicinski
2018-07-23 21:52 ` Tal Gilboa
2018-07-23 22:14 ` Jakub Kicinski
2018-07-23 23:59 ` Alex G.
2018-07-24 13:39 ` Tal Gilboa [this message]
2018-07-30 23:26 ` Alex_Gagniuc
2018-07-31 6:40 ` Tal Gilboa
2018-07-31 15:10 ` Alex G.
2018-08-05 7:05 ` Tal Gilboa
2018-08-06 18:39 ` Alex_Gagniuc
2018-08-06 19:46 ` Bjorn Helgaas
2018-08-06 23:25 ` [PATCH v6 1/9] " Alexandru Gagniuc
2018-08-06 23:25 ` [PATCH v6 2/9] bnx2x: Do not call pcie_print_link_status() Alexandru Gagniuc
2018-08-06 23:25 ` [PATCH v6 3/9] bnxt_en: " Alexandru Gagniuc
2018-08-06 23:25 ` [PATCH v6 4/9] cxgb4: " Alexandru Gagniuc
2018-08-06 23:25 ` [PATCH v6 5/9] fm10k: " Alexandru Gagniuc
2018-08-07 17:52 ` Jeff Kirsher
2018-08-06 23:25 ` [PATCH v6 6/9] ixgbe: " Alexandru Gagniuc
2018-08-07 17:51 ` Jeff Kirsher
2018-08-06 23:25 ` [PATCH v6 7/9] net/mlx4: " Alexandru Gagniuc
2018-08-08 6:10 ` Leon Romanovsky
2018-08-06 23:25 ` [PATCH v6 8/9] net/mlx5: " Alexandru Gagniuc
2018-08-08 6:08 ` Leon Romanovsky
2018-08-08 14:23 ` Tal Gilboa
2018-08-08 15:41 ` Leon Romanovsky
2018-08-08 15:56 ` Tal Gilboa
2018-08-08 16:33 ` Alex G.
2018-08-08 17:27 ` Leon Romanovsky
2018-08-09 14:02 ` Bjorn Helgaas
2018-08-06 23:25 ` [PATCH v6 9/9] nfp: " Alexandru Gagniuc
2018-08-07 19:44 ` [PATCH v6 1/9] PCI: Check for PCIe downtraining conditions David Miller
2018-08-07 21:41 ` Bjorn Helgaas
2018-07-18 13:38 ` [PATCH v3] " Tal Gilboa
2018-07-19 15:49 ` Alex G.
2018-07-23 5:21 ` Tal Gilboa
2018-07-23 17:01 ` Alex G.
2018-07-23 21:35 ` Tal Gilboa
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