slab: remove SLUB_CPU_PARTIAL

We have removed the partial slab usage from allocation paths. Now remove
the whole config option and associated code.

Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Hao Li <hao.li@linux.dev>
Reviewed-by: Suren Baghdasaryan <surenb@google.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

Author: tehcaster

mm/Kconfig

@@ -247,17 +247,6 @@ config SLUB_STATS
 	  out which slabs are relevant to a particular load.
 	  Try running: slabinfo -DA
 
-config SLUB_CPU_PARTIAL
-	default y
-	depends on SMP && !SLUB_TINY
-	bool "Enable per cpu partial caches"
-	help
-	  Per cpu partial caches accelerate objects allocation and freeing
-	  that is local to a processor at the price of more indeterminism
-	  in the latency of the free. On overflow these caches will be cleared
-	  which requires the taking of locks that may cause latency spikes.
-	  Typically one would choose no for a realtime system.
-
 config RANDOM_KMALLOC_CACHES
 	default n
 	depends on !SLUB_TINY

mm/slab.h

@@ -77,12 +77,6 @@ struct slab {
 					struct llist_node llnode;
 					void *flush_freelist;
 				};
-#ifdef CONFIG_SLUB_CPU_PARTIAL
-				struct {
-					struct slab *next;
-					int slabs;	/* Nr of slabs left */
-				};
-#endif
 			};
 			/* Double-word boundary */
 			struct freelist_counters;
@@ -188,23 +182,6 @@ static inline size_t slab_size(const struct slab *slab)
 	return PAGE_SIZE << slab_order(slab);
 }
 
-#ifdef CONFIG_SLUB_CPU_PARTIAL
-#define slub_percpu_partial(c)			((c)->partial)
-
-#define slub_set_percpu_partial(c, p)		\
-({						\
-	slub_percpu_partial(c) = (p)->next;	\
-})
-
-#define slub_percpu_partial_read_once(c)	READ_ONCE(slub_percpu_partial(c))
-#else
-#define slub_percpu_partial(c)			NULL
-
-#define slub_set_percpu_partial(c, p)
-
-#define slub_percpu_partial_read_once(c)	NULL
-#endif // CONFIG_SLUB_CPU_PARTIAL
-
 /*
  * Word size structure that can be atomically updated or read and that
  * contains both the order and the number of objects that a slab of the
@@ -228,12 +205,6 @@ struct kmem_cache {
 	unsigned int object_size;	/* Object size without metadata */
 	struct reciprocal_value reciprocal_size;
 	unsigned int offset;		/* Free pointer offset */
-#ifdef CONFIG_SLUB_CPU_PARTIAL
-	/* Number of per cpu partial objects to keep around */
-	unsigned int cpu_partial;
-	/* Number of per cpu partial slabs to keep around */
-	unsigned int cpu_partial_slabs;
-#endif
 	unsigned int sheaf_capacity;
 	struct kmem_cache_order_objects oo;