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/sysfs-class-net-phydev | 75 ++++++++++++++++++++++++ 1 file changed, 75 insertions(+) create mode 100644 Documentation/ABI/testing/sysfs-class-net-phydev (limited to 'Documentation/ABI/testing/sysfs-class-net-phydev') diff --git a/Documentation/ABI/testing/sysfs-class-net-phydev b/Documentation/ABI/testing/sysfs-class-net-phydev new file mode 100644 index 000000000..31615c59b --- /dev/null +++ b/Documentation/ABI/testing/sysfs-class-net-phydev @@ -0,0 +1,75 @@ +What: /sys/class/mdio_bus///attached_dev +Date: May 2017 +KernelVersion: 4.13 +Contact: netdev@vger.kernel.org +Description: + Symbolic link to the network device this PHY device is + attached to. + +What: /sys/class/mdio_bus///phy_has_fixups +Date: February 2014 +KernelVersion: 3.15 +Contact: netdev@vger.kernel.org +Description: + This attribute contains the boolean value whether a given PHY + device has had any "fixup" workaround running on it, encoded as + a boolean. This information is provided to help troubleshooting + PHY configurations. + +What: /sys/class/mdio_bus///phy_id +Date: November 2012 +KernelVersion: 3.8 +Contact: netdev@vger.kernel.org +Description: + This attribute contains the 32-bit PHY Identifier as reported + by the device during bus enumeration, encoded in hexadecimal. + This ID is used to match the device with the appropriate + driver. + +What: /sys/class/mdio_bus///c45_phy_ids/mmd_device_id +Date: June 2025 +KernelVersion: 6.17 +Contact: netdev@vger.kernel.org +Description: + This attribute contains the 32-bit PHY Identifier as reported + by the device during bus enumeration, encoded in hexadecimal. + These C45 IDs are used to match the device with the appropriate + driver. These files are invisible to the C22 device. + +What: /sys/class/mdio_bus///phy_interface +Date: February 2014 +KernelVersion: 3.15 +Contact: netdev@vger.kernel.org +Description: + This attribute contains the PHY interface as configured by the + Ethernet driver during bus enumeration, encoded in string. + This interface mode is used to configure the Ethernet MAC with the + appropriate mode for its data lines to the PHY hardware. + + Possible values are: + + (not available), mii, gmii, sgmii, tbi, rev-mii, + rmii, rgmii, rgmii-id, rgmii-rxid, rgmii-txid, rtbi, smii + xgmii, moca, qsgmii, trgmii, 1000base-x, 2500base-x, rxaui, + xaui, 10gbase-kr, unknown + +What: /sys/class/mdio_bus///phy_standalone +Date: May 2019 +KernelVersion: 5.3 +Contact: netdev@vger.kernel.org +Description: + Boolean value indicating whether the PHY device is used in + standalone mode, without a net_device associated, by PHYLINK. + Attribute created only when this is the case. + +What: /sys/class/mdio_bus///phy_dev_flags +Date: March 2021 +KernelVersion: 5.13 +Contact: netdev@vger.kernel.org +Description: + 32-bit hexadecimal number representing a bit mask of the + configuration bits passed from the consumer of the PHY + (Ethernet MAC, switch, etc.) to the PHY driver. The flags are + only used internally by the kernel and their placement are + not meant to be stable across kernel versions. This is intended + for facilitating the debugging of PHY drivers. -- cgit v1.3.1