linux-kernel - Re: [PATCH v4] debugobjects: scale the static pool size

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Date:   Fri, 23 Nov 2018 22:01:20 -0500
From:   Qian Cai <cai@....us>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Waiman Long <longman@...hat.com>,
        Yang Shi <yang.shi@...ux.alibaba.com>, arnd@...db.de,
        linux kernel <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v4] debugobjects: scale the static pool size



> On Nov 22, 2018, at 4:56 PM, Thomas Gleixner <tglx@...utronix.de> wrote:
> 
> On Tue, 20 Nov 2018, Qian Cai wrote:
> 
> Looking deeper at that.
> 
>> diff --git a/lib/debugobjects.c b/lib/debugobjects.c
>> index 70935ed91125..140571aa483c 100644
>> --- a/lib/debugobjects.c
>> +++ b/lib/debugobjects.c
>> @@ -23,9 +23,81 @@
>> #define ODEBUG_HASH_BITS	14
>> #define ODEBUG_HASH_SIZE	(1 << ODEBUG_HASH_BITS)
>> 
>> -#define ODEBUG_POOL_SIZE	1024
>> +#define ODEBUG_DEFAULT_POOL	512
>> #define ODEBUG_POOL_MIN_LEVEL	256
>> 
>> +/*
>> + * Some debug objects are allocated during the early boot. Enabling some options
>> + * like timers or workqueue objects may increase the size required significantly
>> + * with large number of CPUs. For example (as today, 20 Nov. 2018),
>> + *
>> + * No. CPUs x 2 (worker pool) objects:
>> + *
>> + * start_kernel
>> + *   workqueue_init_early
>> + *     init_worker_pool
>> + *       init_timer_key
>> + *         debug_object_init
>> + *
>> + * No. CPUs objects (CONFIG_HIGH_RES_TIMERS):
>> + *
>> + * sched_init
>> + *   hrtick_rq_init
>> + *     hrtimer_init
>> + *
>> + * CONFIG_DEBUG_OBJECTS_WORK:
>> + * No. CPUs x 6 (workqueue) objects:
>> + *
>> + * workqueue_init_early
>> + *   alloc_workqueue
>> + *     __alloc_workqueue_key
>> + *       alloc_and_link_pwqs
>> + *         init_pwq
>> + *
>> + * Also, plus No. CPUs objects:
>> + *
>> + * perf_event_init
>> + *    __init_srcu_struct
>> + *      init_srcu_struct_fields
>> + *        init_srcu_struct_nodes
>> + *          __init_work
> 
> None of the things are actually used or required _BEFORE_
> debug_objects_mem_init() is invoked.
> 
> The reason why the call is at this place in start_kernel() is
> historical. It's because back in the days when debugobjects were added the
> memory allocator was enabled way later than today. So we can just move the
> debug_objects_mem_init() call right before sched_init() I think.

Well, now that kmemleak_init() seems complains that debug_objects_mem_init()
is called before it.

[    0.078805] kmemleak: Cannot insert 0xc000000dff930000 into the object search tree (overlaps existing)
[    0.078860] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 4.20.0-rc3+ #3
[    0.078883] Call Trace:
[    0.078904] [c000000001c8fcd0] [c000000000c96b34] dump_stack+0xe8/0x164 (unreliable)
[    0.078935] [c000000001c8fd20] [c000000000486e84] create_object+0x344/0x380
[    0.078962] [c000000001c8fde0] [c000000000489544] early_alloc+0x108/0x1f8
[    0.078989] [c000000001c8fe20] [c00000000109738c] kmemleak_init+0x1d8/0x3d4
[    0.079016] [c000000001c8ff00] [c000000001054028] start_kernel+0x5c0/0x6f8
[    0.079043] [c000000001c8ff90] [c00000000000ae7c] start_here_common+0x1c/0x520
[    0.079070] kmemleak: Kernel memory leak detector disabled
[    0.079091] kmemleak: Object 0xc000000ffd587b68 (size 40):
[    0.079112] kmemleak:   comm "swapper/0", pid 0, jiffies 4294937299
[    0.079135] kmemleak:   min_count = -1
[    0.079153] kmemleak:   count = 0
[    0.079170] kmemleak:   flags = 0x5
[    0.079188] kmemleak:   checksum = 0
[    0.079206] kmemleak:   backtrace:
[    0.079227]      __debug_object_init+0x688/0x700
[    0.079250]      debug_object_activate+0x1e0/0x350
[    0.079272]      __call_rcu+0x60/0x430
[    0.079292]      put_object+0x60/0x80
[    0.079311]      kmemleak_init+0x2cc/0x3d4
[    0.079331]      start_kernel+0x5c0/0x6f8
[    0.079351]      start_here_common+0x1c/0x520
[    0.079380] kmemleak: Early log backtrace:
[    0.079399]    memblock_alloc_try_nid_raw+0x90/0xcc
[    0.079421]    sparse_init_nid+0x144/0x51c
[    0.079440]    sparse_init+0x1a0/0x238
[    0.079459]    initmem_init+0x1d8/0x25c
[    0.079498]    setup_arch+0x3e0/0x464
[    0.079517]    start_kernel+0xa4/0x6f8
[    0.079536]    start_here_common+0x1c/0x520