Changes in sysfs-class-net-queues

6025b913 - net: dqs: add NIC stall detector based on BQL

Mon, 04 Mar 2024 14:08:47 +0000

net: dqs: add NIC stall detector based on BQLsoftnet_data->time_squeeze is sometimes used as a proxy forhost overload or indication of scheduling problems. In practicethis statistic is very noisy and has hard to grasp units -e.g. is 10 squeezes a second to be expected, or high?Delaying network (NAPI) processing leads to drops on NIC queuesbut also RTT bloat, impacting pacing and CA decisions.Stalls are a little hard to detect on the Rx side, becausethere may simply have not been any packets received in givenperiod of time. Packet timestamps help a little bit, butagain we don't know if packets are stale because we'renot keeping up or because someone (*cough* cgroups)disabled IRQs for a long time.We can, however, use Tx as a proxy for Rx stalls. Most driversuse combined Rx+Tx NAPIs so if Tx gets starved so will Rx.On the Tx side we know exactly when packets get queued,and completed, so there is no uncertainty.This patch adds stall checks to BQL. Why BQL? Becauseit's a convenient place to add such checks, alreadycalled by most drivers, and it has copious free spacein its structures (this patch adds no extra cachereferences or dirtying to the fast path).The algorithm takes one parameter - max delay AKA stallthreshold and increments a counter whenever NAPI got delayedfor at least that amount of time. It also records the lengthof the longest stall.To be precise every time NAPI has not polled for at leaststall thrs we check if there were any Tx packets queuedbetween last NAPI run and now - stall_thrs/2.Unlike the classic Tx watchdog this mechanism does notignore stalls caused by Tx being disabled, or loss of link.I don't think the check is worth the complexity, andstall is a stall, whether due to host overload, flowcontrol, link down... doesn't matter much to the application.We have been running this detector in production at Metafor 2 years, with the threshold of 8ms. It's the lowestvalue where false positives become rare. There's stilla constant stream of reported stalls (especially withoutthe ksoftirqd deferral patches reverted), those who liketheir stall metrics to be 0 may prefer higher value.Signed-off-by: Jakub Kicinski Signed-off-by: Breno Leitao Signed-off-by: David S. Miller List of files: /linux-6.15/Documentation/ABI/testing/sysfs-class-net-queues

ae3f4b44 - net: sysfs: Fix /sys/class/net/ path

Wed, 31 Jan 2024 10:21:49 +0000

net: sysfs: Fix /sys/class/net/ pathThe documentation is pointing to the wrong path for the interface.Documentation is pointing to /sys/class/, instead of/sys/class/net/.Fix it by adding the `net/` directory before the interface.Fixes: 1a02ef76acfa ("net: sysfs: add documentation entries for /sys/class//queues")Signed-off-by: Breno Leitao Link: https://lore.kernel.org/r/20240131102150.728960-2-leitao@debian.orgSigned-off-by: Jakub Kicinski List of files: /linux-6.15/Documentation/ABI/testing/sysfs-class-net-queues

ebab9426 - Documentation/ABI: Fix typos

Mon, 14 Aug 2023 21:28:20 +0000

Documentation/ABI: Fix typosFix typos in Documentation/ABI. The changes are in descriptions orcomments where they shouldn't affect use of the ABIs.Signed-off-by: Bjorn Helgaas Reviewed-by: Randy Dunlap Link: https://lore.kernel.org/r/20230814212822.193684-2-helgaas@kernel.orgSigned-off-by: Jonathan Corbet List of files: /linux-6.15/Documentation/ABI/testing/sysfs-class-net-queues

a4fd1f4b - Documentation: Add explanation for XPS using Rx-queue(s) map

Sat, 30 Jun 2018 04:27:12 +0000

Documentation: Add explanation for XPS using Rx-queue(s) mapSigned-off-by: Amritha Nambiar Signed-off-by: David S. Miller List of files: /linux-6.15/Documentation/ABI/testing/sysfs-class-net-queues

822b3b2e - net: Add max rate tx queue attribute

Wed, 18 Mar 2015 12:57:33 +0000

net: Add max rate tx queue attributeThis adds a tx_maxrate attribute to the tx queue sysfs entry allowingfor max-rate limiting. Along with DCB-ETS and BQL this provides anotherknob to tune queue performance. The limit units are Mbps.By default it is disabled. To disable the rate limitation after ithas been set for a queue, it should be set to zero.Signed-off-by: John Fastabend Signed-off-by: Or Gerlitz Signed-off-by: David S. Miller List of files: /linux-6.15/Documentation/ABI/testing/sysfs-class-net-queues

1a02ef76 - net: sysfs: add documentation entries for /sys/class//queues

Fri, 23 May 2014 23:35:41 +0000

net: sysfs: add documentation entries for /sys/class//queuesAdd sysfs documentation for the various attributes of a networkinterface exposed in /sys/class//queues/{rx,tx}-/Signed-off-by: Florian Fainelli Signed-off-by: David S. Miller List of files: /linux-6.15/Documentation/ABI/testing/sysfs-class-net-queues