6.13-stable review patch. If anyone has any objections, please let me know.
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From: Marco Leogrande leogrande@google.com
[ Upstream commit 9a5b021cb8186f1854bac2812bd4f396bb1e881c ]
When a workqueue is created with `WQ_UNBOUND`, its work items are served by special worker-pools, whose host workers are not bound to any specific CPU. In the default configuration (i.e. when `queue_delayed_work` and friends do not specify which CPU to run the work item on), `WQ_UNBOUND` allows the work item to be executed on any CPU in the same node of the CPU it was enqueued on. While this solution potentially sacrifices locality, it avoids contention with other processes that might dominate the CPU time of the processor the work item was scheduled on.
This is not just a theoretical problem: in a particular scenario misconfigured process was hogging most of the time from CPU0, leaving less than 0.5% of its CPU time to the kworker. The IDPF workqueues that were using the kworker on CPU0 suffered large completion delays as a result, causing performance degradation, timeouts and eventual system crash.
Tested:
* I have also run a manual test to gauge the performance improvement. The test consists of an antagonist process (`./stress --cpu 2`) consuming as much of CPU 0 as possible. This process is run under `taskset 01` to bind it to CPU0, and its priority is changed with `chrt -pQ 9900 10000 ${pid}` and `renice -n -20 ${pid}` after start.
Then, the IDPF driver is forced to prefer CPU0 by editing all calls to `queue_delayed_work`, `mod_delayed_work`, etc... to use CPU 0.
Finally, `ktraces` for the workqueue events are collected.
Without the current patch, the antagonist process can force arbitrary delays between `workqueue_queue_work` and `workqueue_execute_start`, that in my tests were as high as `30ms`. With the current patch applied, the workqueue can be migrated to another unloaded CPU in the same node, and, keeping everything else equal, the maximum delay I could see was `6us`.
Fixes: 0fe45467a104 ("idpf: add create vport and netdev configuration") Signed-off-by: Marco Leogrande leogrande@google.com Signed-off-by: Manoj Vishwanathan manojvishy@google.com Signed-off-by: Brian Vazquez brianvv@google.com Reviewed-by: Jacob Keller jacob.e.keller@intel.com Reviewed-by: Pavan Kumar Linga pavan.kumar.linga@intel.com Tested-by: Krishneil Singh krishneil.k.singh@intel.com Signed-off-by: Tony Nguyen anthony.l.nguyen@intel.com Signed-off-by: Sasha Levin sashal@kernel.org --- drivers/net/ethernet/intel/idpf/idpf_main.c | 15 ++++++++++----- 1 file changed, 10 insertions(+), 5 deletions(-)
diff --git a/drivers/net/ethernet/intel/idpf/idpf_main.c b/drivers/net/ethernet/intel/idpf/idpf_main.c index f71d3182580b6..b6c515d14cbf0 100644 --- a/drivers/net/ethernet/intel/idpf/idpf_main.c +++ b/drivers/net/ethernet/intel/idpf/idpf_main.c @@ -174,7 +174,8 @@ static int idpf_probe(struct pci_dev *pdev, const struct pci_device_id *ent) pci_set_master(pdev); pci_set_drvdata(pdev, adapter);
- adapter->init_wq = alloc_workqueue("%s-%s-init", 0, 0, + adapter->init_wq = alloc_workqueue("%s-%s-init", + WQ_UNBOUND | WQ_MEM_RECLAIM, 0, dev_driver_string(dev), dev_name(dev)); if (!adapter->init_wq) { @@ -183,7 +184,8 @@ static int idpf_probe(struct pci_dev *pdev, const struct pci_device_id *ent) goto err_free; }
- adapter->serv_wq = alloc_workqueue("%s-%s-service", 0, 0, + adapter->serv_wq = alloc_workqueue("%s-%s-service", + WQ_UNBOUND | WQ_MEM_RECLAIM, 0, dev_driver_string(dev), dev_name(dev)); if (!adapter->serv_wq) { @@ -192,7 +194,8 @@ static int idpf_probe(struct pci_dev *pdev, const struct pci_device_id *ent) goto err_serv_wq_alloc; }
- adapter->mbx_wq = alloc_workqueue("%s-%s-mbx", 0, 0, + adapter->mbx_wq = alloc_workqueue("%s-%s-mbx", + WQ_UNBOUND | WQ_MEM_RECLAIM, 0, dev_driver_string(dev), dev_name(dev)); if (!adapter->mbx_wq) { @@ -201,7 +204,8 @@ static int idpf_probe(struct pci_dev *pdev, const struct pci_device_id *ent) goto err_mbx_wq_alloc; }
- adapter->stats_wq = alloc_workqueue("%s-%s-stats", 0, 0, + adapter->stats_wq = alloc_workqueue("%s-%s-stats", + WQ_UNBOUND | WQ_MEM_RECLAIM, 0, dev_driver_string(dev), dev_name(dev)); if (!adapter->stats_wq) { @@ -210,7 +214,8 @@ static int idpf_probe(struct pci_dev *pdev, const struct pci_device_id *ent) goto err_stats_wq_alloc; }
- adapter->vc_event_wq = alloc_workqueue("%s-%s-vc_event", 0, 0, + adapter->vc_event_wq = alloc_workqueue("%s-%s-vc_event", + WQ_UNBOUND | WQ_MEM_RECLAIM, 0, dev_driver_string(dev), dev_name(dev)); if (!adapter->vc_event_wq) {