This patch-set is originated from one of the patches that have been posted earlier as a part of "Task_isolation" mode [1] patch series by Alex Belits <abelits@xxxxxxxxxxx>. There are only a couple of changes that I am proposing in this patch-set compared to what Alex has posted earlier. Context ======= On a broad level, all three patches that are included in this patch set are meant to improve the driver/library to respect isolated CPUs by not pinning any job on it. Not doing so could impact the latency values in RT use-cases. Patches ======= * Patch1: The first patch is meant to make cpumask_local_spread() aware of the isolated CPUs. It ensures that the CPUs that are returned by this API only includes housekeeping CPUs. * Patch2: This patch ensures that a probe function that is called using work_on_cpu() doesn't run any task on an isolated CPU. * Patch3: This patch makes store_rps_map() aware of the isolated CPUs so that rps don't queue any jobs on an isolated CPU. Proposed Changes ================ To fix the above-mentioned issues Alex has used housekeeping_cpumask(). The only changes that I am proposing here are: - Removing the dependency on CONFIG_TASK_ISOLATION that was proposed by Alex. As it should be safe to rely on housekeeping_cpumask() even when we don't have any isolated CPUs and we want to fall back to using all available CPUs in any of the above scenarios. - Using both HK_FLAG_DOMAIN and HK_FLAG_WQ in Patch2 & 3, this is because we would want the above fixes not only when we have isolcpus but also with something like systemd's CPU affinity. Testing ======= * Patch 1: Fix for cpumask_local_spread() is tested by creating VFs, loading iavf module and by adding a tracepoint to confirm that only housekeeping CPUs are picked when an appropriate profile is set up and all remaining CPUs when no CPU isolation is configured. * Patch 2: To test the PCI fix, I hotplugged a virtio-net-pci from qemu console and forced its addition to a specific node to trigger the code path that includes the proposed fix and verified that only housekeeping CPUs are included via tracepoint. * Patch 3: To test the fix in store_rps_map(), I tried configuring an isolated CPU by writing to /sys/class/net/en*/queues/rx*/rps_cpus which resulted in 'write error: Invalid argument' error. For the case where a non-isolated CPU is writing in rps_cpus the above operation succeeded without any error. Changes from v3[2]: ================== - In patch 1, replaced HK_FLAG_WQ with HK_FLAG_MANAGED_IRQ based on the suggestion from Frederic Weisbecker. Changes from v2[3]: ================== Both the following suggestions are from Peter Zijlstra. - Patch1: Removed the extra while loop from cpumask_local_spread and fixed the code styling issues. - Patch3: Change to use cpumask_empty() for verifying that the requested CPUs are available in the the housekeeping CPUs. Changes from v1[4]: ================== - Included the suggestions made by Bjorn Helgaas in the commit message. - Included the 'Reviewed-by' and 'Acked-by' received for Patch-2. [1] https://patchwork.ozlabs.org/project/netdev/patch/51102eebe62336c6a4e584c7a503553b9f90e01c.camel@xxxxxxxxxxx/ [2] https://patchwork.ozlabs.org/project/linux-pci/cover/20200623192331.215557-1-nitesh@xxxxxxxxxx/ [3] https://patchwork.ozlabs.org/project/linux-pci/cover/20200622234510.240834-1-nitesh@xxxxxxxxxx/ [4] https://patchwork.ozlabs.org/project/linux-pci/cover/20200610161226.424337-1-nitesh@xxxxxxxxxx/ Alex Belits (3): lib: Restrict cpumask_local_spread to houskeeping CPUs PCI: Restrict probe functions to housekeeping CPUs net: Restrict receive packets queuing to housekeeping CPUs drivers/pci/pci-driver.c | 5 ++++- lib/cpumask.c | 16 +++++++++++----- net/core/net-sysfs.c | 10 +++++++++- 3 files changed, 24 insertions(+), 7 deletions(-) --
