linux-kernel - [PATCH] debugobjects: add a new Kconfig for POOL

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Date:   Sun, 18 Nov 2018 03:22:55 -0500
From:   Qian Cai <cai@....us>
To:     akpm@...ux-foundation.org
Cc:     tglx@...utronix.de, longman@...hat.com, yang.shi@...ux.alibaba.com,
        arnd@...db.de, linux-kernel@...r.kernel.org, Qian Cai <cai@....us>
Subject: [PATCH] debugobjects: add a new Kconfig for POOL_SIZE

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.

Signed-off-by: Qian Cai <cai@....us>
---
 lib/Kconfig.debug  | 12 ++++++++++++
 lib/debugobjects.c |  7 ++++++-
 2 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/lib/Kconfig.debug b/lib/Kconfig.debug
index 1af29b8224fd..a4af837649df 100644
--- a/lib/Kconfig.debug
+++ b/lib/Kconfig.debug
@@ -449,6 +449,18 @@ config DEBUG_OBJECTS
 	  kernel to track the life time of various objects and validate
 	  the operations on those objects.
 
+config DEBUG_OBJECTS_POOL_SIZE
+	int "Debug objects pool size"
+	depends on DEBUG_OBJECTS_TIMERS || DEBUG_OBJECTS_WORK
+	default 1024
+	help
+	  Some debug objects are allocated during the early boot. Enable some
+	  config options may requires the sizes below,
+
+	  DEBUG_OBJECTS_TIMERS: No. CPUs x 2 (worker pool) + No. CPUs (hrtimer)
+	  DEBUG_OBJECTS_WORK:   No. CPUs x 2 (worker pool) x 6 (workqueue) +
+				No. CPUs x 2 (worker pool)
+
 config DEBUG_OBJECTS_SELFTEST
 	bool "Debug objects selftest"
 	depends on DEBUG_OBJECTS
diff --git a/lib/debugobjects.c b/lib/debugobjects.c
index 70935ed91125..eb8158538993 100644
--- a/lib/debugobjects.c
+++ b/lib/debugobjects.c
@@ -23,7 +23,12 @@
 #define ODEBUG_HASH_BITS	14
 #define ODEBUG_HASH_SIZE	(1 << ODEBUG_HASH_BITS)
 
-#define ODEBUG_POOL_SIZE	1024
+#ifdef CONFIG_DEBUG_OBJECTS_POOL_SIZE
+#define ODEBUG_POOL_SIZE	CONFIG_DEBUG_OBJECTS_POOL_SIZE
+#else
+#define ODEBUG_POOL_SIZE        1024
+#endif
+
 #define ODEBUG_POOL_MIN_LEVEL	256
 
 #define ODEBUG_CHUNK_SHIFT	PAGE_SHIFT
-- 
2.17.2 (Apple Git-113)