Cache aware scheduling is currently controlled only through global debugfs knobs, but the right aggressiveness is workload and platform specific. A multi-threaded Verilator run is one example: its RSS is large while only a small part of it is hot, so an RSS-based footprint estimate should not decide whether it is aggregated; and packing its threads onto the SMT siblings of one LLC beats spreading them across LLCs on some platforms (e.g. AMD EPYC Turin) but not on others (e.g. EPYC Milan). Such choices cannot be made globally for the whole machine.
This series adds per-process (per mm_struct) control. The first patch splits the llc_aggr_tolerance debugfs knob into independent thread-count and footprint tolerances and hardens the unbounded percentage knobs against multiplication overflow. The second adds prctl(PR_SCHED_CACHE), a single prctl command whose sub-command selects GET or SET, covering a per-process enable, both tolerances and the overaggr percentage, plus an inherit mask choosing which attributes survive execve() (fork() always inherits). The remaining two patches add selftests and documentation. A numactl-like launcher built on this interface, llcctl, is available at: https://github.com/cyyself/llcctl It sets the attributes and the inherit mask on itself and executes the target command, so the whole process tree runs with the requested settings, e.g.: llcctl -d -- ./membw-hungry # opt out, spread across LLCs llcctl -n 2 -p 100 -- make -j16 # pack up to 2 threads/core Tested on x86-64 in QEMU with an EPYC-like topology (128 CPUs, 8 LLC domains of 8 cores / 16 threads each): the selftests pass as both root and an unprivileged user, and aggregation was verified end to end by observing thread placement of a 24-thread spinner with and without llcctl (evenly spread by default; packed into a single LLC with raised tolerances). No new dmesg warnings. Yangyu Chen (4): sched/cache: Split llc_aggr_tolerance into nr and size tolerances sched/cache: Add PR_SCHED_CACHE prctl for per-mm control selftests/prctl: Add PR_SCHED_CACHE tests docs/scheduler: Document cache aware scheduling controls Documentation/scheduler/index.rst | 1 + Documentation/scheduler/sched-cache.rst | 125 ++++++ include/linux/mm_types.h | 10 +- include/linux/sched.h | 16 + include/uapi/linux/prctl.h | 38 ++ kernel/fork.c | 2 +- kernel/sched/debug.c | 6 +- kernel/sched/fair.c | 205 +++++++-- kernel/sched/sched.h | 3 +- kernel/sched/syscalls.c | 120 ++++++ kernel/sys.c | 5 + .../trace/beauty/include/uapi/linux/prctl.h | 37 ++ tools/testing/selftests/prctl/.gitignore | 1 + tools/testing/selftests/prctl/Makefile | 15 +- tools/testing/selftests/prctl/config | 1 + tools/testing/selftests/prctl/sched-cache.c | 394 ++++++++++++++++++ 16 files changed, 931 insertions(+), 48 deletions(-) create mode 100644 Documentation/scheduler/sched-cache.rst create mode 100644 tools/testing/selftests/prctl/sched-cache.c base-commit: 248951ddc14de84de3910f9b13f51491a8cd91df -- 2.47.3
