From: Daniel Wagner <[email protected]> The io_queue flag informs multiqueue device drivers where to place hardware queues. Document this new flag in the isolcpus command-line argument description.
Signed-off-by: Daniel Wagner <[email protected]> Reviewed-by: Hannes Reinecke <[email protected]> [atomlin: Refined io_queue kernel parameter documentation] Signed-off-by: Aaron Tomlin <[email protected]> --- .../admin-guide/kernel-parameters.txt | 30 ++++++++++++++++++- 1 file changed, 29 insertions(+), 1 deletion(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index cf3807641d89..e2d798351964 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2810,7 +2810,6 @@ Kernel parameters "number of CPUs in system - 1". managed_irq - Isolate from being targeted by managed interrupts which have an interrupt mask containing isolated CPUs. The affinity of managed interrupts is @@ -2833,6 +2832,35 @@ Kernel parameters housekeeping CPUs has no influence on those queues. + io_queue + Applicable to managed IRQs only. Restrict + multiqueue hardware queue allocation to online + housekeeping CPUs. This guarantees that all + managed hardware completion interrupts are routed + exclusively to housekeeping cores, shielding + isolated CPUs from I/O interruptions even if they + initiated the request. + + The io_queue configuration takes precedence over + managed_irq. When io_queue is used, managed_irq + placement constraints have no effect. + + Note: Using io_queue restricts the number of + allocated hardware queues to match the number of + housekeeping CPUs. This prevents MSI-X vector + exhaustion and forces isolated CPUs to share + submission queues. + + Note: Offlining housekeeping CPUs which serve + isolated CPUs will fail. The isolated CPUs must + be offlined before offlining the housekeeping + CPUs. + + Note: When I/O is submitted by an application on + an isolated CPU, the hardware completion + interrupt is handled entirely by a housekeeping + CPU. + The format of <cpu-list> is described above. iucv= [HW,NET] -- 2.51.0
