Messages in this thread |  | | From | Joel Fernandes <> | Date | Tue, 24 Nov 2020 10:08:01 -0500 | Subject | Re: [PATCH -tip 00/32] Core scheduling (v9) |
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On Tue, Nov 24, 2020 at 6:48 AM Vincent Guittot <vincent.guittot@linaro.org> wrote: > > Hi Joel, > > On Wed, 18 Nov 2020 at 00:20, Joel Fernandes (Google) > <joel@joelfernandes.org> wrote: > > > > Core-Scheduling > > =============== > > Enclosed is series v9 of core scheduling. > > v9 is rebased on tip/master (fe4adf6f92c4 ("Merge branch 'irq/core'")).. > > I hope that this version is acceptable to be merged (pending any new review > > ./scripts/get_maintainer.pl is quite useful to make sure that all > maintainers are cced and helps a lot to get some reviews
Apologies. I was just going by folks who were CC'd on previous series. I am new to doing this series's postings. Sorry if I missed you and will run get_maintainers henceforth!
- Joel
> > comments that arise) as the main issues in the past are all resolved: > > 1. Vruntime comparison. > > 2. Documentation updates. > > 3. CGroup and per-task interface developed by Google and Oracle. > > 4. Hotplug fixes. > > Almost all patches also have Reviewed-by or Acked-by tag. See below for full > > list of changes in v9. > > > > Introduction of feature > > ======================= > > Core scheduling is a feature that allows only trusted tasks to run > > concurrently on cpus sharing compute resources (eg: hyperthreads on a > > core). The goal is to mitigate the core-level side-channel attacks > > without requiring to disable SMT (which has a significant impact on > > performance in some situations). Core scheduling (as of v7) mitigates > > user-space to user-space attacks and user to kernel attack when one of > > the siblings enters the kernel via interrupts or system call. > > > > By default, the feature doesn't change any of the current scheduler > > behavior. The user decides which tasks can run simultaneously on the > > same core (for now by having them in the same tagged cgroup). When a tag > > is enabled in a cgroup and a task from that cgroup is running on a > > hardware thread, the scheduler ensures that only idle or trusted tasks > > run on the other sibling(s). Besides security concerns, this feature can > > also be beneficial for RT and performance applications where we want to > > control how tasks make use of SMT dynamically. > > > > Both a CGroup and Per-task interface via prctl(2) are provided for configuring > > core sharing. More details are provided in documentation patch. Kselftests are > > provided to verify the correctness/rules of the interface. > > > > Testing > > ======= > > ChromeOS testing shows 300% improvement in keypress latency on a Google > > docs key press with Google hangout test (the maximum latency drops from 150ms > > to 50ms for keypresses). > > > > Julien: TPCC tests showed improvements with core-scheduling as below. With kernel > > protection enabled, it does not show any regression. Possibly ASI will improve > > the performance for those who choose kernel protection (can be toggled through > > sched_core_protect_kernel sysctl). > > average stdev diff > > baseline (SMT on) 1197.272 44.78312824 > > core sched ( kernel protect) 412.9895 45.42734343 -65.51% > > core sched (no kernel protect) 686.6515 71.77756931 -42.65% > > nosmt 408.667 39.39042872 -65.87% > > (Note these results are from v8). > > > > Vineeth tested sysbench and does not see any regressions. > > Hong and Aubrey tested v9 and see results similar to v8. There is a known issue > > with uperf that does regress. This appears to be because of ksoftirq heavily > > contending with other tasks on the core. The consensus is this can be improved > > in the future. > > > > Changes in v9 > > ============= > > - Note that the vruntime snapshot change is written in 2 patches to show the > > progression of the idea and prevent merge conflicts: > > sched/fair: Snapshot the min_vruntime of CPUs on force idle > > sched: Improve snapshotting of min_vruntime for CGroups > > Same with the RT priority inversion change: > > sched: Fix priority inversion of cookied task with sibling > > sched: Improve snapshotting of min_vruntime for CGroups > > - Disable coresched on certain AMD HW. > > > > Changes in v8 > > ============= > > - New interface/API implementation > > - Joel > > - Revised kernel protection patch > > - Joel > > - Revised Hotplug fixes > > - Joel > > - Minor bug fixes and address review comments > > - Vineeth > > > > Changes in v7 > > ============= > > - Kernel protection from untrusted usermode tasks > > - Joel, Vineeth > > - Fix for hotplug crashes and hangs > > - Joel, Vineeth > > > > Changes in v6 > > ============= > > - Documentation > > - Joel > > - Pause siblings on entering nmi/irq/softirq > > - Joel, Vineeth > > - Fix for RCU crash > > - Joel > > - Fix for a crash in pick_next_task > > - Yu Chen, Vineeth > > - Minor re-write of core-wide vruntime comparison > > - Aaron Lu > > - Cleanup: Address Review comments > > - Cleanup: Remove hotplug support (for now) > > - Build fixes: 32 bit, SMT=n, AUTOGROUP=n etc > > - Joel, Vineeth > > > > Changes in v5 > > ============= > > - Fixes for cgroup/process tagging during corner cases like cgroup > > destroy, task moving across cgroups etc > > - Tim Chen > > - Coresched aware task migrations > > - Aubrey Li > > - Other minor stability fixes. > > > > Changes in v4 > > ============= > > - Implement a core wide min_vruntime for vruntime comparison of tasks > > across cpus in a core. > > - Aaron Lu > > - Fixes a typo bug in setting the forced_idle cpu. > > - Aaron Lu > > > > Changes in v3 > > ============= > > - Fixes the issue of sibling picking up an incompatible task > > - Aaron Lu > > - Vineeth Pillai > > - Julien Desfossez > > - Fixes the issue of starving threads due to forced idle > > - Peter Zijlstra > > - Fixes the refcounting issue when deleting a cgroup with tag > > - Julien Desfossez > > - Fixes a crash during cpu offline/online with coresched enabled > > - Vineeth Pillai > > - Fixes a comparison logic issue in sched_core_find > > - Aaron Lu > > > > Changes in v2 > > ============= > > - Fixes for couple of NULL pointer dereference crashes > > - Subhra Mazumdar > > - Tim Chen > > - Improves priority comparison logic for process in different cpus > > - Peter Zijlstra > > - Aaron Lu > > - Fixes a hard lockup in rq locking > > - Vineeth Pillai > > - Julien Desfossez > > - Fixes a performance issue seen on IO heavy workloads > > - Vineeth Pillai > > - Julien Desfossez > > - Fix for 32bit build > > - Aubrey Li > > > > Future work > > =========== > > - Load balancing/Migration fixes for core scheduling. > > With v6, Load balancing is partially coresched aware, but has some > > issues w.r.t process/taskgroup weights: > > https://lwn.net/ml/linux-kernel/20200225034438.GA617271@z... > > > > Aubrey Li (1): > > sched: migration changes for core scheduling > > > > Joel Fernandes (Google) (16): > > sched/fair: Snapshot the min_vruntime of CPUs on force idle > > sched: Enqueue task into core queue only after vruntime is updated > > sched: Simplify the core pick loop for optimized case > > sched: Improve snapshotting of min_vruntime for CGroups > > arch/x86: Add a new TIF flag for untrusted tasks > > kernel/entry: Add support for core-wide protection of kernel-mode > > entry/idle: Enter and exit kernel protection during idle entry and > > exit > > sched: Split the cookie and setup per-task cookie on fork > > sched: Add a per-thread core scheduling interface > > sched: Release references to the per-task cookie on exit > > sched/debug: Add CGroup node for printing group cookie if SCHED_DEBUG > > kselftest: Add tests for core-sched interface > > sched: Move core-scheduler interfacing code to a new file > > Documentation: Add core scheduling documentation > > sched: Add a coresched command line option > > sched: Debug bits... > > > > Josh Don (2): > > sched: Refactor core cookie into struct > > sched: Add a second-level tag for nested CGroup usecase > > > > Peter Zijlstra (11): > > sched: Wrap rq::lock access > > sched: Introduce sched_class::pick_task() > > sched/fair: Fix pick_task_fair crashes due to empty rbtree > > sched: Core-wide rq->lock > > sched/fair: Add a few assertions > > sched: Basic tracking of matching tasks > > sched: Add core wide task selection and scheduling. > > sched: Fix priority inversion of cookied task with sibling > > sched: Trivial forced-newidle balancer > > irq_work: Cleanup > > sched: CGroup tagging interface for core scheduling > > > > Vineeth Pillai (2): > > sched/fair: Fix forced idle sibling starvation corner case > > entry/kvm: Protect the kernel when entering from guest > > > > .../admin-guide/hw-vuln/core-scheduling.rst | 330 +++++ > > Documentation/admin-guide/hw-vuln/index.rst | 1 + > > .../admin-guide/kernel-parameters.txt | 25 + > > arch/x86/include/asm/thread_info.h | 2 + > > arch/x86/kernel/cpu/bugs.c | 19 + > > arch/x86/kvm/x86.c | 2 + > > drivers/gpu/drm/i915/i915_request.c | 4 +- > > include/linux/cpu.h | 1 + > > include/linux/entry-common.h | 30 +- > > include/linux/entry-kvm.h | 12 + > > include/linux/irq_work.h | 33 +- > > include/linux/irqflags.h | 4 +- > > include/linux/sched.h | 28 +- > > include/linux/sched/smt.h | 4 + > > include/uapi/linux/prctl.h | 3 + > > kernel/Kconfig.preempt | 5 + > > kernel/bpf/stackmap.c | 2 +- > > kernel/cpu.c | 43 + > > kernel/entry/common.c | 28 +- > > kernel/entry/kvm.c | 33 + > > kernel/fork.c | 1 + > > kernel/irq_work.c | 18 +- > > kernel/printk/printk.c | 6 +- > > kernel/rcu/tree.c | 3 +- > > kernel/sched/Makefile | 1 + > > kernel/sched/core.c | 1278 +++++++++++++++-- > > kernel/sched/coretag.c | 819 +++++++++++ > > kernel/sched/cpuacct.c | 12 +- > > kernel/sched/deadline.c | 38 +- > > kernel/sched/debug.c | 12 +- > > kernel/sched/fair.c | 313 +++- > > kernel/sched/idle.c | 24 +- > > kernel/sched/pelt.h | 2 +- > > kernel/sched/rt.c | 31 +- > > kernel/sched/sched.h | 315 +++- > > kernel/sched/stop_task.c | 14 +- > > kernel/sched/topology.c | 4 +- > > kernel/sys.c | 3 + > > kernel/time/tick-sched.c | 6 +- > > kernel/trace/bpf_trace.c | 2 +- > > tools/include/uapi/linux/prctl.h | 3 + > > tools/testing/selftests/sched/.gitignore | 1 + > > tools/testing/selftests/sched/Makefile | 14 + > > tools/testing/selftests/sched/config | 1 + > > .../testing/selftests/sched/test_coresched.c | 818 +++++++++++ > > 45 files changed, 4033 insertions(+), 315 deletions(-) > > create mode 100644 Documentation/admin-guide/hw-vuln/core-scheduling.rst > > create mode 100644 kernel/sched/coretag.c > > create mode 100644 tools/testing/selftests/sched/.gitignore > > create mode 100644 tools/testing/selftests/sched/Makefile > > create mode 100644 tools/testing/selftests/sched/config > > create mode 100644 tools/testing/selftests/sched/test_coresched.c > > > > -- > > 2.29.2.299.gdc1121823c-goog > >
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