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SubjectRe: [RFC PATCH v2 00/17] Core scheduling v2
On Wed, Apr 24, 2019 at 12:18 AM Vineeth Remanan Pillai
<vpillai@digitalocean.com> wrote:
>
> Second iteration of the core-scheduling feature.
>
> This version fixes apparent bugs and performance issues in v1. This
> doesn't fully address the issue of core sharing between processes
> with different tags. Core sharing still happens 1% to 5% of the time
> based on the nature of workload and timing of the runnable processes.
>
> Changes in v2
> -------------
> - rebased on mainline commit: 6d906f99817951e2257d577656899da02bb33105
> - Fixes for couple of NULL pointer dereference crashes
> - Subhra Mazumdar
> - Tim Chen

Is this one missed? Or fixed with a better impl?

The boot up CPUs don't match the possible cpu map, so the not onlined
CPU rq->core are not initialized, which causes NULL pointer dereference
panic in online_fair_sched_group():

Thanks,
-Aubrey

diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 85c728d..bdabf20 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -10492,6 +10492,10 @@ void online_fair_sched_group(struct task_group *tg)
rq = cpu_rq(i);
se = tg->se[i];

+#ifdef CONFIG_SCHED_CORE
+ if (!rq->core)
+ continue;
+#endif
raw_spin_lock_irq(rq_lockp(rq));
update_rq_clock(rq);
attach_entity_cfs_rq(se);
> - 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
>
> Issues
> ------
> - Processes with different tags can still share the core
> - A crash when disabling cpus with core-scheduling on
> - https://paste.debian.net/plainh/fa6bcfa8
>
> ---
>
> Peter Zijlstra (16):
> stop_machine: Fix stop_cpus_in_progress ordering
> sched: Fix kerneldoc comment for ia64_set_curr_task
> sched: Wrap rq::lock access
> sched/{rt,deadline}: Fix set_next_task vs pick_next_task
> sched: Add task_struct pointer to sched_class::set_curr_task
> sched/fair: Export newidle_balance()
> sched: Allow put_prev_task() to drop rq->lock
> sched: Rework pick_next_task() slow-path
> sched: Introduce sched_class::pick_task()
> sched: Core-wide rq->lock
> sched: Basic tracking of matching tasks
> sched: A quick and dirty cgroup tagging interface
> sched: Add core wide task selection and scheduling.
> sched/fair: Add a few assertions
> sched: Trivial forced-newidle balancer
> sched: Debug bits...
>
> Vineeth Remanan Pillai (1):
> sched: Wake up sibling if it has something to run
>
> include/linux/sched.h | 9 +-
> kernel/Kconfig.preempt | 7 +-
> kernel/sched/core.c | 800 +++++++++++++++++++++++++++++++++++++--
> kernel/sched/cpuacct.c | 12 +-
> kernel/sched/deadline.c | 99 +++--
> kernel/sched/debug.c | 4 +-
> kernel/sched/fair.c | 137 +++++--
> kernel/sched/idle.c | 42 +-
> kernel/sched/pelt.h | 2 +-
> kernel/sched/rt.c | 96 +++--
> kernel/sched/sched.h | 185 ++++++---
> kernel/sched/stop_task.c | 35 +-
> kernel/sched/topology.c | 4 +-
> kernel/stop_machine.c | 2 +
> 14 files changed, 1145 insertions(+), 289 deletions(-)
>
> --
> 2.17.1
>

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