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 --- .../ABI/testing/sysfs-class-net-statistics | 217 +++++++++++++++++++++ 1 file changed, 217 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-net-statistics (limited to 'Documentation/ABI/testing/sysfs-class-net-statistics') diff --git a/Documentation/ABI/testing/sysfs-class-net-statistics b/Documentation/ABI/testing/sysfs-class-net-statistics new file mode 100644 index 000000000..53e508c69 --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-net-statistics @@ -0,0 +1,217 @@ +What: /sys/class/net//statistics/collisions +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of collisions seen by this network device. + This value might not be relevant with all MAC layers. + +What: /sys/class/net//statistics/multicast +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of multicast packets received by this + network device. + +What: /sys/class/net//statistics/rx_bytes +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of bytes received by this network device. + See the network driver for the exact meaning of when this + value is incremented. + +What: /sys/class/net//statistics/rx_compressed +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of compressed packets received by this + network device. This value might only be relevant for interfaces + that support packet compression (e.g: PPP). + +What: /sys/class/net//statistics/rx_crc_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets received with a CRC (FCS) error + by this network device. Note that the specific meaning might + depend on the MAC layer used by the interface. + +What: /sys/class/net//statistics/rx_dropped +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets received by the network device + but dropped, that are not forwarded to the upper layers for + packet processing. See the network driver for the exact + meaning of this value. + +What: /sys/class/net//statistics/rx_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of receive errors on this network device. + See the network driver for the exact meaning of this value. + +What: /sys/class/net//statistics/rx_fifo_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of receive FIFO errors seen by this + network device. See the network driver for the exact + meaning of this value. + +What: /sys/class/net//statistics/rx_frame_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of received frames with error, such as + alignment errors. Note that the specific meaning depends on + on the MAC layer protocol used. See the network driver for + the exact meaning of this value. + +What: /sys/class/net//statistics/rx_length_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of received error packet with a length + error, oversized or undersized. See the network driver for the + exact meaning of this value. + +What: /sys/class/net//statistics/rx_missed_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of received packets that have been missed + due to lack of capacity in the receive side. See the network + driver for the exact meaning of this value. + +What: /sys/class/net//statistics/rx_nohandler +Date: February 2016 +KernelVersion: 4.6 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of received packets that were dropped on + an inactive device by the network core. + +What: /sys/class/net//statistics/rx_over_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of received packets that are oversized + compared to what the network device is configured to accept + (e.g: larger than MTU). See the network driver for the exact + meaning of this value. + +What: /sys/class/net//statistics/rx_packets +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the total number of good packets received by this + network device. + +What: /sys/class/net//statistics/tx_aborted_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets that have been aborted + during transmission by a network device (e.g: because of + a medium collision). See the network driver for the exact + meaning of this value. + +What: /sys/class/net//statistics/tx_bytes +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of bytes transmitted by a network + device. See the network driver for the exact meaning of this + value, in particular whether this accounts for all successfully + transmitted packets or all packets that have been queued for + transmission. + +What: /sys/class/net//statistics/tx_carrier_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets that could not be transmitted + because of carrier errors (e.g: physical link down). See the + network driver for the exact meaning of this value. + +What: /sys/class/net//statistics/tx_compressed +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of transmitted compressed packets. Note + this might only be relevant for devices that support + compression (e.g: PPP). + +What: /sys/class/net//statistics/tx_dropped +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets dropped during transmission. + See the driver for the exact reasons as to why the packets were + dropped. + +What: /sys/class/net//statistics/tx_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets in error during transmission by + a network device. See the driver for the exact reasons as to + why the packets were dropped. + +What: /sys/class/net//statistics/tx_fifo_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets having caused a transmit + FIFO error. See the driver for the exact reasons as to why the + packets were dropped. + +What: /sys/class/net//statistics/tx_heartbeat_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets transmitted that have been + reported as heartbeat errors. See the driver for the exact + reasons as to why the packets were dropped. + +What: /sys/class/net//statistics/tx_packets +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets transmitted by a network + device. See the driver for whether this reports the number of all + attempted or successful transmissions. + +What: /sys/class/net//statistics/tx_window_errors +Date: April 2005 +KernelVersion: 2.6.12 +Contact: netdev@vger.kernel.org +Description: + Indicates the number of packets not successfully transmitted + due to a window collision. The specific meaning depends on the + MAC layer used. On Ethernet this is usually used to report + late collisions errors. -- cgit v1.3.1