slub: Replace cmpxchg_double() (6801be4f) · Commits · EulixOS / Software / Kernel

include/linux/slub_def.h

+9 −3

Original line number	Diff line number	Diff line
		@@ -39,7 +39,8 @@ enum stat_item {
		CPU_PARTIAL_FREE, /* Refill cpu partial on free */
		CPU_PARTIAL_NODE, /* Refill cpu partial from node partial */
		CPU_PARTIAL_DRAIN, /* Drain cpu partial to node partial */
		NR_SLUB_STAT_ITEMS };
		NR_SLUB_STAT_ITEMS
		};

		#ifndef CONFIG_SLUB_TINY
		/*
		@@ -47,8 +48,13 @@ enum stat_item {
		* with this_cpu_cmpxchg_double() alignment requirements.
		*/
		struct kmem_cache_cpu {
		union {
		struct {
		void *freelist; / Pointer to next available object */
		unsigned long tid; /* Globally unique transaction id */
		};
		freelist_aba_t freelist_tid;
		};
		struct slab slab; / The slab from which we are allocating */
		#ifdef CONFIG_SLUB_CPU_PARTIAL
		struct slab partial; / Partially allocated frozen slabs */

mm/slab.h

+46 −7

Original line number	Diff line number	Diff line
		@@ -6,6 +6,38 @@
		*/
		void __init kmem_cache_init(void);

		#ifdef CONFIG_64BIT
		# ifdef system_has_cmpxchg128
		# define system_has_freelist_aba() system_has_cmpxchg128()
		# define try_cmpxchg_freelist try_cmpxchg128
		# endif
		#define this_cpu_try_cmpxchg_freelist this_cpu_try_cmpxchg128
		typedef u128 freelist_full_t;
		#else /* CONFIG_64BIT */
		# ifdef system_has_cmpxchg64
		# define system_has_freelist_aba() system_has_cmpxchg64()
		# define try_cmpxchg_freelist try_cmpxchg64
		# endif
		#define this_cpu_try_cmpxchg_freelist this_cpu_try_cmpxchg64
		typedef u64 freelist_full_t;
		#endif /* CONFIG_64BIT */

		#if defined(system_has_freelist_aba) && !defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
		#undef system_has_freelist_aba
		#endif

		/*
		* Freelist pointer and counter to cmpxchg together, avoids the typical ABA
		* problems with cmpxchg of just a pointer.
		*/
		typedef union {
		struct {
		void *freelist;
		unsigned long counter;
		};
		freelist_full_t full;
		} freelist_aba_t;

		/* Reuses the bits in struct page */
		struct slab {
		unsigned long __page_flags;
		@@ -38,6 +70,8 @@ struct slab {
		#endif
		};
		/* Double-word boundary */
		union {
		struct {
		void freelist; / first free object */
		union {
		unsigned long counters;
		@@ -48,6 +82,11 @@ struct slab {
		};
		};
		};
		#ifdef system_has_freelist_aba
		freelist_aba_t freelist_counter;
		#endif
		};
		};
		struct rcu_head rcu_head;
		};
		unsigned int __unused;
		@@ -72,8 +111,8 @@ SLAB_MATCH(memcg_data, memcg_data);
		#endif
		#undef SLAB_MATCH
		static_assert(sizeof(struct slab) <= sizeof(struct page));
		#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && defined(CONFIG_SLUB)
		static_assert(IS_ALIGNED(offsetof(struct slab, freelist), 2sizeof(void )));
		#if defined(system_has_freelist_aba) && defined(CONFIG_SLUB)
		static_assert(IS_ALIGNED(offsetof(struct slab, freelist), sizeof(freelist_aba_t)));
		#endif

		/**

mm/slub.c

+82 −57

Original line number	Diff line number	Diff line
		@@ -292,7 +292,12 @@ static inline bool kmem_cache_has_cpu_partial(struct kmem_cache *s)
		/* Poison object */
		#define __OBJECT_POISON ((slab_flags_t __force)0x80000000U)
		/* Use cmpxchg_double */

		#ifdef system_has_freelist_aba
		#define __CMPXCHG_DOUBLE ((slab_flags_t __force)0x40000000U)
		#else
		#define __CMPXCHG_DOUBLE ((slab_flags_t __force)0U)
		#endif

		/*
		* Tracking user of a slab.
		@@ -512,6 +517,40 @@ static __always_inline void slab_unlock(struct slab *slab)
		__bit_spin_unlock(PG_locked, &page->flags);
		}

		static inline bool
		__update_freelist_fast(struct slab *slab,
		void *freelist_old, unsigned long counters_old,
		void *freelist_new, unsigned long counters_new)
		{
		#ifdef system_has_freelist_aba
		freelist_aba_t old = { .freelist = freelist_old, .counter = counters_old };
		freelist_aba_t new = { .freelist = freelist_new, .counter = counters_new };

		return try_cmpxchg_freelist(&slab->freelist_counter.full, &old.full, new.full);
		#else
		return false;
		#endif
		}

		static inline bool
		__update_freelist_slow(struct slab *slab,
		void *freelist_old, unsigned long counters_old,
		void *freelist_new, unsigned long counters_new)
		{
		bool ret = false;

		slab_lock(slab);
		if (slab->freelist == freelist_old &&
		slab->counters == counters_old) {
		slab->freelist = freelist_new;
		slab->counters = counters_new;
		ret = true;
		}
		slab_unlock(slab);

		return ret;
		}

		/*
		* Interrupts must be disabled (for the fallback code to work right), typically
		* by an _irqsave() lock variant. On PREEMPT_RT the preempt_disable(), which is
		@@ -519,33 +558,25 @@ static __always_inline void slab_unlock(struct slab *slab)
		* allocation/ free operation in hardirq context. Therefore nothing can
		* interrupt the operation.
		*/
		static inline bool __cmpxchg_double_slab(struct kmem_cache s, struct slab slab,
		static inline bool __slab_update_freelist(struct kmem_cache s, struct slab slab,
		void *freelist_old, unsigned long counters_old,
		void *freelist_new, unsigned long counters_new,
		const char *n)
		{
		bool ret;

		if (USE_LOCKLESS_FAST_PATH())
		lockdep_assert_irqs_disabled();
		#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
		defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)

		if (s->flags & __CMPXCHG_DOUBLE) {
		if (cmpxchg_double(&slab->freelist, &slab->counters,
		freelist_old, counters_old,
		freelist_new, counters_new))
		return true;
		} else
		#endif
		{
		slab_lock(slab);
		if (slab->freelist == freelist_old &&
		slab->counters == counters_old) {
		slab->freelist = freelist_new;
		slab->counters = counters_new;
		slab_unlock(slab);
		return true;
		}
		slab_unlock(slab);
		ret = __update_freelist_fast(slab, freelist_old, counters_old,
		freelist_new, counters_new);
		} else {
		ret = __update_freelist_slow(slab, freelist_old, counters_old,
		freelist_new, counters_new);
		}
		if (likely(ret))
		return true;

		cpu_relax();
		stat(s, CMPXCHG_DOUBLE_FAIL);
		@@ -557,36 +588,26 @@ static inline bool __cmpxchg_double_slab(struct kmem_cache s, struct slab slab
		return false;
		}

		static inline bool cmpxchg_double_slab(struct kmem_cache s, struct slab slab,
		static inline bool slab_update_freelist(struct kmem_cache s, struct slab slab,
		void *freelist_old, unsigned long counters_old,
		void *freelist_new, unsigned long counters_new,
		const char *n)
		{
		#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
		defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
		bool ret;

		if (s->flags & __CMPXCHG_DOUBLE) {
		if (cmpxchg_double(&slab->freelist, &slab->counters,
		freelist_old, counters_old,
		freelist_new, counters_new))
		return true;
		} else
		#endif
		{
		ret = __update_freelist_fast(slab, freelist_old, counters_old,
		freelist_new, counters_new);
		} else {
		unsigned long flags;

		local_irq_save(flags);
		slab_lock(slab);
		if (slab->freelist == freelist_old &&
		slab->counters == counters_old) {
		slab->freelist = freelist_new;
		slab->counters = counters_new;
		slab_unlock(slab);
		local_irq_restore(flags);
		return true;
		}
		slab_unlock(slab);
		ret = __update_freelist_slow(slab, freelist_old, counters_old,
		freelist_new, counters_new);
		local_irq_restore(flags);
		}
		if (likely(ret))
		return true;

		cpu_relax();
		stat(s, CMPXCHG_DOUBLE_FAIL);
		@@ -2228,7 +2249,7 @@ static inline void acquire_slab(struct kmem_cache s,
		VM_BUG_ON(new.frozen);
		new.frozen = 1;

		if (!__cmpxchg_double_slab(s, slab,
		if (!__slab_update_freelist(s, slab,
		freelist, counters,
		new.freelist, new.counters,
		"acquire_slab"))
		@@ -2554,7 +2575,7 @@ static void deactivate_slab(struct kmem_cache s, struct slab slab,
		}


		if (!cmpxchg_double_slab(s, slab,
		if (!slab_update_freelist(s, slab,
		old.freelist, old.counters,
		new.freelist, new.counters,
		"unfreezing slab")) {
		@@ -2611,7 +2632,7 @@ static void __unfreeze_partials(struct kmem_cache s, struct slab partial_slab)

		new.frozen = 0;

		} while (!__cmpxchg_double_slab(s, slab,
		} while (!__slab_update_freelist(s, slab,
		old.freelist, old.counters,
		new.freelist, new.counters,
		"unfreezing slab"));
		@@ -3008,6 +3029,18 @@ static inline bool pfmemalloc_match(struct slab *slab, gfp_t gfpflags)
		}

		#ifndef CONFIG_SLUB_TINY
		static inline bool
		__update_cpu_freelist_fast(struct kmem_cache *s,
		void freelist_old, void freelist_new,
		unsigned long tid)
		{
		freelist_aba_t old = { .freelist = freelist_old, .counter = tid };
		freelist_aba_t new = { .freelist = freelist_new, .counter = next_tid(tid) };

		return this_cpu_try_cmpxchg_freelist(s->cpu_slab->freelist_tid.full,
		&old.full, new.full);
		}

		/*
		* Check the slab->freelist and either transfer the freelist to the
		* per cpu freelist or deactivate the slab.
		@@ -3034,7 +3067,7 @@ static inline void get_freelist(struct kmem_cache s, struct slab *slab)
		new.inuse = slab->objects;
		new.frozen = freelist != NULL;

		} while (!__cmpxchg_double_slab(s, slab,
		} while (!__slab_update_freelist(s, slab,
		freelist, counters,
		NULL, new.counters,
		"get_freelist"));
		@@ -3359,11 +3392,7 @@ static __always_inline void __slab_alloc_node(struct kmem_cache s,
		* against code executing on this cpu not from access by
		* other cpus.
		*/
		if (unlikely(!this_cpu_cmpxchg_double(
		s->cpu_slab->freelist, s->cpu_slab->tid,
		object, tid,
		next_object, next_tid(tid)))) {

		if (unlikely(!__update_cpu_freelist_fast(s, object, next_object, tid))) {
		note_cmpxchg_failure("slab_alloc", s, tid);
		goto redo;
		}
		@@ -3631,7 +3660,7 @@ static void __slab_free(struct kmem_cache s, struct slab slab,
		}
		}

		} while (!cmpxchg_double_slab(s, slab,
		} while (!slab_update_freelist(s, slab,
		prior, counters,
		head, new.counters,
		"__slab_free"));
		@@ -3736,11 +3765,7 @@ static __always_inline void do_slab_free(struct kmem_cache *s,

		set_freepointer(s, tail_obj, freelist);

		if (unlikely(!this_cpu_cmpxchg_double(
		s->cpu_slab->freelist, s->cpu_slab->tid,
		freelist, tid,
		head, next_tid(tid)))) {

		if (unlikely(!__update_cpu_freelist_fast(s, freelist, head, tid))) {
		note_cmpxchg_failure("slab_free", s, tid);
		goto redo;
		}
		@@ -4505,11 +4530,11 @@ static int kmem_cache_open(struct kmem_cache *s, slab_flags_t flags)
		}
		}

		#if defined(CONFIG_HAVE_CMPXCHG_DOUBLE) && \
		defined(CONFIG_HAVE_ALIGNED_STRUCT_PAGE)
		if (system_has_cmpxchg_double() && (s->flags & SLAB_NO_CMPXCHG) == 0)
		#ifdef system_has_freelist_aba
		if (system_has_freelist_aba() && !(s->flags & SLAB_NO_CMPXCHG)) {
		/* Enable fast mode */
		s->flags \|= __CMPXCHG_DOUBLE;
		}
		#endif

		/*