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[98.195.139.126]) by smtp.gmail.com with ESMTPSA id t3-v6sm1502421oie.52.2018.09.05.06.52.32 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 05 Sep 2018 06:52:33 -0700 (PDT) Subject: Re: [PATCH 1/9] PCI: sysfs: Export available PCIe bandwidth To: Stephen Hemminger Cc: linux-pci@vger.kernel.org, bhelgaas@google.com, keith.busch@intel.com, alex_gagniuc@dellteam.com, austin_bolen@dell.com, shyam_iyer@dell.com, Ariel Elior , everest-linux-l2@cavium.com, "David S. Miller" , Michael Chan , Ganesh Goudar , Jeff Kirsher , Tariq Toukan , Saeed Mahameed , Leon Romanovsky , Jakub Kicinski , Dirk van der Merwe , netdev@vger.kernel.org, linux-kernel@vger.kernel.org, intel-wired-lan@lists.osuosl.org, linux-rdma@vger.kernel.org, oss-drivers@netronome.com References: <20180903180242.14504-1-mr.nuke.me@gmail.com> <20180903180242.14504-2-mr.nuke.me@gmail.com> <20180905082605.69d9e5a0@shemminger-XPS-13-9360> From: "Alex G." Message-ID: <122e86e4-7c0a-8539-75dc-1515c1b8c68f@gmail.com> Date: Wed, 5 Sep 2018 08:52:31 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <20180905082605.69d9e5a0@shemminger-XPS-13-9360> Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 09/05/2018 02:26 AM, Stephen Hemminger wrote: > On Mon, 3 Sep 2018 13:02:28 -0500 > Alexandru Gagniuc wrote: > >> For certain bandwidth-critical devices (e.g. multi-port network cards) >> it is useful to know the available bandwidth to the root complex. This >> information is only available via the system log, which doesn't >> account for link degradation after probing. >> >> With a sysfs attribute, we can computes the bandwidth on-demand, and >> will detect degraded links. >> >> Signed-off-by: Alexandru Gagniuc > > In other places (like /sys/class/net/eth0/speed) only the raw value is printed > without suffix. The general convention in sysfs is that it should be one value > per file and in more raw format. So why not just print it in bits/sec without > suffix? I wanted to be consistent with other PCIe exports that use units.For example: /sys/devices/pci0000:3a/0000:3a:00.0/0000:3b:00.0/0000:3c:05.0/max_link_speed:8 GT/s /sys/devices/pci0000:3a/0000:3a:00.0/0000:3b:00.0/0000:3c:05.0/current_link_speed:2.5 GT/s /sys/bus/pci/slots/182/cur_bus_speed:2.5 GT/s PCIe /sys/bus/pci/slots/182/max_bus_speed:8.0 GT/s PCIe