[RFT for v9] (Was Re: [PATCH v8 -tip 00/26] Core scheduling)

[Joel Fernandes]

All,

I am getting ready to send the next v9 series based on tip/master
branch. Could you please give the below tree a try and report any results in
your testing?
git tree:
https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git (branch coresched)
git log:
https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/log/?h=coresched

The major changes in this series are the improvements:
(1)
"sched: Make snapshotting of min_vruntime more CGroup-friendly"
https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/commit/?h=coresched-v9-for-test&id=9a20a6652b3c50fd51faa829f7947004239a04eb

(2)
"sched: Simplify the core pick loop for optimized case"
https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/commit/?h=coresched-v9-for-test&id=0370117b4fd418cdaaa6b1489bfc14f305691152

And a bug fix:
(1)
"sched: Enqueue task into core queue only after vruntime is updated"
https://git.kernel.org/pub/scm/linux/kernel/git/jfern/linux.git/commit/?h=coresched-v9-for-test&id=401dad5536e7e05d1299d0864e6fc5072029f492

There are also 2 more bug fixes that I squashed-in related to kernel
protection and a crash seen on the tip/master branch.

Hoping to send the series next week out to the list.

Have a great weekend, and Thanks!

 - Joel


On Mon, Oct 19, 2020 at 09:43:10PM -0400, Joel Fernandes (Google) wrote:
> Eighth iteration of the Core-Scheduling 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.
> 
> This iteration focuses on the the following stuff:
> - Redesigned API.
> - Rework of Kernel Protection feature based on Thomas's entry work.
> - Rework of hotplug fixes.
> - Address review comments in v7
> 
> Joel: 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.
> 
> Julien: TPCC tests showed improvements with core-scheduling. 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). Results:
> v8				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%
> 
> v8 is rebased on tip/master.
> 
> 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...
> - Core scheduling test framework: kselftests, torture tests etc
> 
> 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
> 
> Aubrey Li (1):
> sched: migration changes for core scheduling
> 
> Joel Fernandes (Google) (13):
> sched/fair: Snapshot the min_vruntime of CPUs on force idle
> 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: Add a second-level tag for nested CGroup usecase
> sched: Release references to the per-task cookie on exit
> sched: Handle task addition to CGroup
> 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
> 
> Peter Zijlstra (10):
> sched: Wrap rq::lock access
> sched: Introduce sched_class::pick_task()
> 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: Trivial forced-newidle balancer
> irq_work: Cleanup
> sched: cgroup tagging interface for core scheduling
> sched: Debug bits...
> 
> 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   |  312 +++++
> Documentation/admin-guide/hw-vuln/index.rst   |    1 +
> .../admin-guide/kernel-parameters.txt         |    7 +
> arch/x86/include/asm/thread_info.h            |    2 +
> arch/x86/kvm/x86.c                            |    3 +
> drivers/gpu/drm/i915/i915_request.c           |    4 +-
> include/linux/entry-common.h                  |   20 +-
> include/linux/entry-kvm.h                     |   12 +
> include/linux/irq_work.h                      |   33 +-
> include/linux/irqflags.h                      |    4 +-
> include/linux/sched.h                         |   27 +-
> include/uapi/linux/prctl.h                    |    3 +
> kernel/Kconfig.preempt                        |    6 +
> kernel/bpf/stackmap.c                         |    2 +-
> kernel/entry/common.c                         |   25 +-
> kernel/entry/kvm.c                            |   13 +
> 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                           | 1135 ++++++++++++++++-
> kernel/sched/coretag.c                        |  468 +++++++
> kernel/sched/cpuacct.c                        |   12 +-
> kernel/sched/deadline.c                       |   34 +-
> kernel/sched/debug.c                          |    8 +-
> kernel/sched/fair.c                           |  272 ++--
> kernel/sched/idle.c                           |   24 +-
> kernel/sched/pelt.h                           |    2 +-
> kernel/sched/rt.c                             |   22 +-
> kernel/sched/sched.h                          |  302 ++++-
> kernel/sched/stop_task.c                      |   13 +-
> 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  |  840 ++++++++++++
> 41 files changed, 3437 insertions(+), 232 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
> 
> --
> 2.29.0.rc1.297.gfa9743e501-goog
>