Re: [PATCH] debugobjects: add a new Kconfig for POOL_SIZE

Thomas Gleixner
2018-11-18T18:21:35Z

Qian,

On Sun, 18 Nov 2018, Qian Cai wrote:

> The current value of ODEBUG_POOL_SIZE is not big enough for large memory
> systems with timer or/and workqueue objects because during the early
> boot, timer objects needs at least the size equals to
>
> No. CPUs x 2 (worker pool)
>
> start_kernel
> workqueue_init_early
> init_worker_pool
> init_timer_key
> debug_object_init
>
> puls, No. CPUs
>
> start_kernel
> sched_init
> hrtimer_init
> debug_object_init
>
> Then, workqueue objects requires even more,
>
> No. CPUs x 2 (worker pool) x 6 (workqueue)
>
> start_kernel
> workqueue_init_early
> __alloc_workqueue_key
> alloc_workqueue
> init_pwq
> debug_object_init
>
> plus, No, CPUs x 2 (worker pool)
>
> start_kernel
> perf_event_init
> __init_srcu_struct
> init_srcu_struct_fields
> __init_work
> debug_object_init
>
> As the results, systems have 60+ CPUs with both timer and workqueue
> objects enabled could trigger "ODEBUG: Out of memory. ODEBUG disabled".
>
> Hence, add a new Kconfig option so users could adjust ODEBUG_POOL_SIZE
> accordingly if either timer or workqueue objects are selected.

why do we need a config option, when the required number can be deduced
already from the active CONFIG_DEBUG_OBJECTS_* and NR_CPUS?

Thanks,

tglx