From 0d6526f82c3cdefcca47f73f5fc08dc6f335eac6 Mon Sep 17 00:00:00 2001 From: Tim Chen Date: Mon, 21 Sep 2026 17:37:22 -0700 Subject: sched/cache: Keep nr_pref_llc_running in the runnable domain, to fix LLC mis-scheduling bug alb_break_llc() decides whether to break LLC preference during active load balance. It does so by testing that every runnable fair task on the source rq prefers its LLC: env->src_rq->nr_pref_llc_running == env->src_rq->cfs.h_nr_runnable But the two counters cover different sets. nr_pref_llc_running is updated in account_llc_enqueue()/account_llc_dequeue(), next to cfs_rq->nr_queued, so it follows queued tasks. h_nr_runnable is updated in set_delayed()/ clear_delayed() and drops delay-dequeued tasks. So under DELAY_DEQUEUE, a preferring task that goes to sleep stays counted in nr_pref_llc_running while h_nr_runnable falls. The equality then breaks, alb_break_llc() returns false, and active balance is free to pull a task off its preferred LLC. Active balance only moves runnable tasks, and this is the only LLC check it consults: once the stopper runs, LBF_ACTIVE_LB skips the per-task test in can_migrate_task(). The runnable set is the one we want. Fix it on the counter side. A task should be counted in nr_pref_llc_running exactly while it is both queued on its preferred LLC (pref_llc_queued) and runnable (!sched_delayed). Define that membership once in task_pref_llc_runnable(), and adjust the counter only through pref_llc_running_inc()/pref_llc_running_dec() from the four sites that change either input: account_llc_enqueue(), account_llc_dequeue(), set_delayed() and clear_delayed(). Gating every update on the same predicate keeps the delay, wake and dequeue paths from double-counting or underflowing; see the comments at those sites for the ordering. nr_llc_running and sd->llc_counts are not touched and stay on queued semantics. Fixes: 714059f79ff0 ("sched/cache: Handle moving single tasks to/from their preferred LLC") Closes: https://lore.kernel.org/lkml/20260827135000.735138-1-zhanxusheng@xiaomi.com/ Reported-by: Zhan Xusheng Suggested-by: Chen Yu Signed-off-by: Tim Chen Signed-off-by: Peter Zijlstra (Intel) Signed-off-by: Ingo Molnar Reviewed-by: Kayra Cizmeci Cc: # v7.2.x Link: https://patch.msgid.link/06af61afedac32e6477f57feb4d658f6c411c3af.1790035273.git.tim.c.chen@linux.intel.com --- Documentation/ABI/testing/debugfs-driver-qat | 109 +++++++++++++++++++++++++++ 1 file changed, 109 insertions(+) create mode 100644 Documentation/ABI/testing/debugfs-driver-qat (limited to 'Documentation/ABI/testing/debugfs-driver-qat') diff --git a/Documentation/ABI/testing/debugfs-driver-qat b/Documentation/ABI/testing/debugfs-driver-qat new file mode 100644 index 000000000..3f1efbbad --- /dev/null +++ b/Documentation/ABI/testing/debugfs-driver-qat @@ -0,0 +1,109 @@ +What: /sys/kernel/debug/qat__/fw_counters +Date: November 2023 +KernelVersion: 6.6 +Contact: qat-linux@intel.com +Description: (RO) Read returns the number of requests sent to the FW and the number of responses + received from the FW for each Acceleration Engine + Reported firmware counters:: + + : Number of requests sent from Acceleration Engine N to FW and responses + Acceleration Engine N received from FW + +What: /sys/kernel/debug/qat__/heartbeat/config +Date: November 2023 +KernelVersion: 6.6 +Contact: qat-linux@intel.com +Description: (RW) Read returns value of the Heartbeat update period. + Write to the file changes this period value. + + This period should reflect planned polling interval of device + health status. High frequency Heartbeat monitoring wastes CPU cycles + but minimizes the customer’s system downtime. Also, if there are + large service requests that take some time to complete, high frequency + Heartbeat monitoring could result in false reports of unresponsiveness + and in those cases, period needs to be increased. + + This parameter is effective only for c3xxx, c62x, dh895xcc devices. + 4xxx has this value internally fixed to 200ms. + + Default value is set to 500. Minimal allowed value is 200. + All values are expressed in milliseconds. + +What: /sys/kernel/debug/qat__/heartbeat/queries_failed +Date: November 2023 +KernelVersion: 6.6 +Contact: qat-linux@intel.com +Description: (RO) Read returns the number of times the device became unresponsive. + + Attribute returns value of the counter which is incremented when + status query results negative. + +What: /sys/kernel/debug/qat__/heartbeat/queries_sent +Date: November 2023 +KernelVersion: 6.6 +Contact: qat-linux@intel.com +Description: (RO) Read returns the number of times the control process checked + if the device is responsive. + + Attribute returns value of the counter which is incremented on + every status query. + +What: /sys/kernel/debug/qat__/heartbeat/status +Date: November 2023 +KernelVersion: 6.6 +Contact: qat-linux@intel.com +Description: (RO) Read returns the device health status. + + Returns 0 when device is healthy or -1 when is unresponsive + or the query failed to send. + + The driver does not monitor for Heartbeat. It is left for a user + to poll the status periodically. + +What: /sys/kernel/debug/qat__/pm_status +Date: January 2024 +KernelVersion: 6.7 +Contact: qat-linux@intel.com +Description: (RO) Read returns power management information specific to the + QAT device. + + This attribute is only available for qat_4xxx and qat_6xxx devices. + +What: /sys/kernel/debug/qat__/cnv_errors +Date: January 2024 +KernelVersion: 6.7 +Contact: qat-linux@intel.com +Description: (RO) Read returns, for each Acceleration Engine (AE), the number + of errors and the type of the last error detected by the device + when performing verified compression. + Reported counters:: + + : Number of Compress and Verify (CnV) errors and type + of the last CnV error detected by Acceleration + Engine N. + +What: /sys/kernel/debug/qat__/heartbeat/inject_error +Date: March 2024 +KernelVersion: 6.8 +Contact: qat-linux@intel.com +Description: (WO) Write to inject an error that simulates an heartbeat + failure. This is to be used for testing purposes. + + After writing this file, the driver stops arbitration on a + random engine and disables the fetching of heartbeat counters. + If a workload is running on the device, a job submitted to the + accelerator might not get a response and a read of the + `heartbeat/status` attribute might report -1, i.e. device + unresponsive. + The error is unrecoverable thus the device must be restarted to + restore its functionality. + + This attribute is available only when the kernel is built with + CONFIG_CRYPTO_DEV_QAT_ERROR_INJECTION=y. + + A write of 1 enables error injection. + + The following example shows how to enable error injection:: + + # cd /sys/kernel/debug/qat__ + # echo 1 > heartbeat/inject_error -- cgit v1.3.1