Implement per-cpu memory allocator

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
Change-Id: I54f43ccec743b7c5311221fac22a0b690a863377

4 files changed, 485 insertions, 1 deletions

diff --git a/include/Makefile.am b/include/Makefile.am
index bc27c39..29bf6c1 100644
--- a/include/Makefile.am
+++ b/include/Makefile.am
@@ -27,6 +27,7 @@ nobase_include_HEADERS = \
 	rseq/compiler.h \
 	rseq/inject.h \
 	rseq/pseudocode.h \
+	rseq/percpu-alloc.h \
 	rseq/rseq.h \
 	rseq/thread-pointer.h \
 	rseq/utils.h
diff --git a/include/rseq/percpu-alloc.h b/include/rseq/percpu-alloc.h
new file mode 100644
index 0000000..c1ea96a
--- /dev/null
+++ b/include/rseq/percpu-alloc.h
@@ -0,0 +1,37 @@
+/* SPDX-License-Identifier: MIT */
+/* SPDX-FileCopyrightText: 2024 Mathieu Desnoyers <mathieu.desnoyers@efficios.com> */
+
+#ifndef _RSEQ_PERCPU_ALLOC_H
+#define _RSEQ_PERCPU_ALLOC_H
+
+#include <stddef.h>
+#include <sys/types.h>
+
+/*
+ * rseq/percpu-alloc.h
+ */
+
+struct rseq_percpu_pool;
+
+struct rseq_percpu_pool *rseq_percpu_pool_create(size_t item_len,
+		size_t percpu_len, int max_nr_cpus,
+		int prot, int flags, int fd, off_t offset);
+int rseq_percpu_pool_destroy(struct rseq_percpu_pool *pool);
+
+void *rseq_percpu_malloc(struct rseq_percpu_pool *pool);
+void *rseq_percpu_zmalloc(struct rseq_percpu_pool *pool);
+void rseq_percpu_free(void *ptr);
+
+void *__rseq_percpu_ptr(void *ptr, int cpu);
+
+#define rseq_percpu_ptr(ptr, cpu)	((__typeof__(ptr)) __rseq_percpu_ptr(ptr, cpu))
+
+struct rseq_percpu_pool_set *rseq_percpu_pool_set_create(void);
+int rseq_percpu_pool_set_destroy(struct rseq_percpu_pool_set *pool_set);
+int rseq_percpu_pool_set_add_pool(struct rseq_percpu_pool_set *pool_set,
+		struct rseq_percpu_pool *pool);
+
+void *rseq_percpu_pool_set_malloc(struct rseq_percpu_pool_set *pool_set, size_t len);
+void *rseq_percpu_pool_set_zmalloc(struct rseq_percpu_pool_set *pool_set, size_t len);
+
+#endif /* _RSEQ_PERCPU_ALLOC_H */
diff --git a/src/Makefile.am b/src/Makefile.am
index ee01bde..c9e134c 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -4,7 +4,7 @@
 lib_LTLIBRARIES = librseq.la
 
 librseq_la_SOURCES = \
-	rseq.c
+	rseq.c rseq-percpu-alloc.c
 
 librseq_la_LDFLAGS = -no-undefined -version-info $(RSEQ_LIBRARY_VERSION)
 librseq_la_LIBADD = $(DL_LIBS)
diff --git a/src/rseq-percpu-alloc.c b/src/rseq-percpu-alloc.c
new file mode 100644
index 0000000..12f8b2b
--- /dev/null
+++ b/src/rseq-percpu-alloc.c
@@ -0,0 +1,446 @@
+// SPDX-License-Identifier: MIT
+// SPDX-FileCopyrightText: 2024 Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
+
+#include <rseq/percpu-alloc.h>
+#include <sys/mman.h>
+#include <assert.h>
+#include <string.h>
+#include <pthread.h>
+#include <unistd.h>
+#include <stdlib.h>
+#include <rseq/compiler.h>
+#include <errno.h>
+#include <stdint.h>
+#include <stdbool.h>
+
+/*
+ * rseq-percpu-alloc.c: rseq per-cpu memory allocator.
+ *
+ * The rseq per-cpu memory allocator allows the application the request
+ * memory pools of per-cpu memory each of a given virtual address size
+ * per-cpu, for a given maximum number of CPUs.
+ */
+
+/* Use lowest bits of per-cpu addresses to index the pool. */
+#if RSEQ_BITS_PER_LONG == 64
+# define OFFSET_SHIFT	16
+#else
+# define OFFSET_SHIFT	8
+#endif
+#define MAX_NR_POOLS	(1U << OFFSET_SHIFT)
+#define POOL_MASK	(MAX_NR_POOLS - 1)
+
+#define POOL_SET_NR_ENTRIES	(RSEQ_BITS_PER_LONG - OFFSET_SHIFT)
+#define POOL_SET_MAX_ALLOC_LEN	(1U << POOL_SET_NR_ENTRIES)
+
+#if RSEQ_BITS_PER_LONG == 64
+# define POOL_SET_MIN_ENTRY	3	/* Smallest item_len=8 */
+#else
+# define POOL_SET_MIN_ENTRY	2	/* Smallest item_len=4 */
+#endif
+
+#define DEFAULT_PAGE_SIZE	4096
+
+struct free_list_node;
+
+struct free_list_node {
+	struct free_list_node *next;
+};
+
+/* This lock protects pool create/destroy. */
+static pthread_mutex_t pool_lock = PTHREAD_MUTEX_INITIALIZER;
+
+struct rseq_percpu_pool {
+	void *base;
+	unsigned int index;
+	size_t item_len;
+	size_t percpu_len;
+	int item_order;
+	int max_nr_cpus;
+
+	/*
+	 * The free list chains freed items on the cpu 0 address range.
+	 * We should rethink this decision if false sharing between
+	 * malloc/free from other cpus and data accesses from cpu 0
+	 * becomes an issue. This is a NULL-terminated singly-linked
+	 * list.
+	 */
+	struct free_list_node *free_list_head;
+	size_t next_unused;
+	/* This lock protects allocation/free within the pool. */
+	pthread_mutex_t lock;
+};
+
+//TODO: the array of pools should grow dynamically on create.
+static struct rseq_percpu_pool rseq_percpu_pool[MAX_NR_POOLS];
+
+/*
+ * Pool set entries are indexed by item_len rounded to the next power of
+ * 2. A pool set can contain NULL pool entries, in which case the next
+ * large enough entry will be used for allocation.
+ */
+struct rseq_percpu_pool_set {
+	/* This lock protects add vs malloc/zmalloc within the pool set. */
+	pthread_mutex_t lock;
+	struct rseq_percpu_pool *entries[POOL_SET_NR_ENTRIES];
+};
+
+#define __rseq_align_mask(v, mask)	(((v) + (mask)) & ~(mask))
+#define rseq_align(v, align)		__rseq_align_mask(v, (__typeof__(v)) (align) - 1)
+
+static __attribute__((unused))
+unsigned int fls_u64(uint64_t x)
+{
+	unsigned int r = 64;
+
+	if (!x)
+		return 0;
+
+	if (!(x & 0xFFFFFFFF00000000ULL)) {
+		x <<= 32;
+		r -= 32;
+	}
+	if (!(x & 0xFFFF000000000000ULL)) {
+		x <<= 16;
+		r -= 16;
+	}
+	if (!(x & 0xFF00000000000000ULL)) {
+		x <<= 8;
+		r -= 8;
+	}
+	if (!(x & 0xF000000000000000ULL)) {
+		x <<= 4;
+		r -= 4;
+	}
+	if (!(x & 0xC000000000000000ULL)) {
+		x <<= 2;
+		r -= 2;
+	}
+	if (!(x & 0x8000000000000000ULL)) {
+		x <<= 1;
+		r -= 1;
+	}
+	return r;
+}
+
+static __attribute__((unused))
+unsigned int fls_u32(uint32_t x)
+{
+	unsigned int r = 32;
+
+	if (!x)
+		return 0;
+	if (!(x & 0xFFFF0000U)) {
+		x <<= 16;
+		r -= 16;
+	}
+	if (!(x & 0xFF000000U)) {
+		x <<= 8;
+		r -= 8;
+	}
+	if (!(x & 0xF0000000U)) {
+		x <<= 4;
+		r -= 4;
+	}
+	if (!(x & 0xC0000000U)) {
+		x <<= 2;
+		r -= 2;
+	}
+	if (!(x & 0x80000000U)) {
+		x <<= 1;
+		r -= 1;
+	}
+	return r;
+}
+
+static
+unsigned int fls_ulong(unsigned long x)
+{
+#if RSEQ_BITS_PER_LONG == 32
+	return fls_u32(x);
+#else
+	return fls_u64(x);
+#endif
+}
+
+/*
+ * Return the minimum order for which x <= (1UL << order).
+ * Return -1 if x is 0.
+ */
+static
+int get_count_order_ulong(unsigned long x)
+{
+	if (!x)
+		return -1;
+
+	return fls_ulong(x - 1);
+}
+
+struct rseq_percpu_pool *rseq_percpu_pool_create(size_t item_len,
+		size_t percpu_len, int max_nr_cpus,
+		int prot, int flags, int fd, off_t offset)
+{
+	struct rseq_percpu_pool *pool;
+	void *base;
+	unsigned int i;
+	int order;
+	long page_len;
+
+	/* Make sure each item is large enough to contain free list pointers. */
+	if (item_len < sizeof(void *))
+		item_len = sizeof(void *);
+
+	/* Align item_len on next power of two. */
+	order = get_count_order_ulong(item_len);
+	if (order < 0) {
+		errno = EINVAL;
+		return NULL;
+	}
+	item_len = 1UL << order;
+
+	/* Align percpu_len on page size. */
+	page_len = sysconf(_SC_PAGE_SIZE);
+	if (page_len < 0)
+		page_len = DEFAULT_PAGE_SIZE;
+	percpu_len = rseq_align(percpu_len, page_len);
+
+	if (max_nr_cpus < 0 || item_len > percpu_len ||
+			percpu_len > (UINTPTR_MAX >> OFFSET_SHIFT)) {
+		errno = EINVAL;
+		return NULL;
+	}
+
+	pthread_mutex_lock(&pool_lock);
+	/* Linear scan in array of pools to find empty spot. */
+	for (i = 0; i < MAX_NR_POOLS; i++) {
+		pool = &rseq_percpu_pool[i];
+		if (!pool->base)
+			goto found_empty;
+	}
+	errno = ENOMEM;
+	pool = NULL;
+	goto end;
+
+found_empty:
+	base = mmap(NULL, percpu_len * max_nr_cpus, prot, flags, fd, offset);
+	if (base == MAP_FAILED) {
+		pool = NULL;
+		goto end;
+	}
+	// TODO: integrate with libnuma to provide NUMA placement hints.
+	// See move_pages(2).
+	pthread_mutex_init(&pool->lock, NULL);
+	pool->base = base;
+	pool->percpu_len = percpu_len;
+	pool->max_nr_cpus = max_nr_cpus;
+	pool->index = i;
+	pool->item_len = item_len;
+	pool->item_order = order;
+end:
+	pthread_mutex_unlock(&pool_lock);
+	return pool;
+}
+
+int rseq_percpu_pool_destroy(struct rseq_percpu_pool *pool)
+{
+	int ret;
+
+	pthread_mutex_lock(&pool_lock);
+	if (!pool->base) {
+		errno = ENOENT;
+		ret = -1;
+		goto end;
+	}
+	ret = munmap(pool->base, pool->percpu_len * pool->max_nr_cpus);
+	if (ret)
+		goto end;
+	pthread_mutex_destroy(&pool->lock);
+	memset(pool, 0, sizeof(*pool));
+end:
+	pthread_mutex_unlock(&pool_lock);
+	return 0;
+}
+
+static
+void *__rseq_pool_percpu_ptr(struct rseq_percpu_pool *pool, int cpu, uintptr_t item_offset)
+{
+	return pool->base + (pool->percpu_len * cpu) + item_offset;
+}
+
+void *__rseq_percpu_ptr(void *_ptr, int cpu)
+{
+	uintptr_t ptr = (uintptr_t) _ptr;
+	uintptr_t item_offset = ptr >> OFFSET_SHIFT;
+	uintptr_t pool_index = ptr & POOL_MASK;
+	struct rseq_percpu_pool *pool = &rseq_percpu_pool[pool_index];
+
+	assert(cpu >= 0);
+	return __rseq_pool_percpu_ptr(pool, cpu, item_offset);
+}
+
+static
+void rseq_percpu_zero_item(struct rseq_percpu_pool *pool, uintptr_t item_offset)
+{
+	int i;
+
+	for (i = 0; i < pool->max_nr_cpus; i++) {
+		char *p = __rseq_pool_percpu_ptr(pool, i, item_offset);
+		memset(p, 0, pool->item_len);
+	}
+}
+
+static
+void *__rseq_percpu_malloc(struct rseq_percpu_pool *pool, bool zeroed)
+{
+	struct free_list_node *node;
+	uintptr_t item_offset;
+	void *addr;
+
+	pthread_mutex_lock(&pool->lock);
+	/* Get first entry from free list. */
+	node = pool->free_list_head;
+	if (node != NULL) {
+		/* Remove node from free list (update head). */
+		pool->free_list_head = node->next;
+		item_offset = (uintptr_t) ((void *) node - pool->base);
+		addr = (void *) ((item_offset << OFFSET_SHIFT) | pool->index);
+		goto end;
+	}
+	if (pool->next_unused + pool->item_len > pool->percpu_len) {
+		addr = NULL;
+		goto end;
+	}
+	item_offset = pool->next_unused;
+	addr = (void *) ((item_offset << OFFSET_SHIFT) | pool->index);
+	pool->next_unused += pool->item_len;
+end:
+	pthread_mutex_unlock(&pool->lock);
+	if (zeroed && addr)
+		rseq_percpu_zero_item(pool, item_offset);
+	return addr;
+}
+
+void *rseq_percpu_malloc(struct rseq_percpu_pool *pool)
+{
+	return __rseq_percpu_malloc(pool, false);
+}
+
+void *rseq_percpu_zmalloc(struct rseq_percpu_pool *pool)
+{
+	return __rseq_percpu_malloc(pool, true);
+}
+
+void rseq_percpu_free(void *_ptr)
+{
+	uintptr_t ptr = (uintptr_t) _ptr;
+	uintptr_t item_offset = ptr >> OFFSET_SHIFT;
+	uintptr_t pool_index = ptr & POOL_MASK;
+	struct rseq_percpu_pool *pool = &rseq_percpu_pool[pool_index];
+	struct free_list_node *head, *item;
+
+	pthread_mutex_lock(&pool->lock);
+	/* Add ptr to head of free list */
+	head = pool->free_list_head;
+	/* Free-list is in cpu 0 range. */
+	item = (struct free_list_node *)__rseq_pool_percpu_ptr(pool, 0, item_offset);
+	item->next = head;
+	pool->free_list_head = item;
+	pthread_mutex_unlock(&pool->lock);
+}
+
+struct rseq_percpu_pool_set *rseq_percpu_pool_set_create(void)
+{
+	struct rseq_percpu_pool_set *pool_set;
+
+	pool_set = calloc(1, sizeof(struct rseq_percpu_pool_set));
+	if (!pool_set)
+		return NULL;
+	pthread_mutex_init(&pool_set->lock, NULL);
+	return pool_set;
+}
+
+int rseq_percpu_pool_set_destroy(struct rseq_percpu_pool_set *pool_set)
+{
+	int order, ret;
+
+	for (order = POOL_SET_MIN_ENTRY; order < POOL_SET_NR_ENTRIES; order++) {
+		struct rseq_percpu_pool *pool = pool_set->entries[order];
+
+		if (!pool)
+			continue;
+		ret = rseq_percpu_pool_destroy(pool);
+		if (ret)
+			return ret;
+		pool_set->entries[order] = NULL;
+	}
+	pthread_mutex_destroy(&pool_set->lock);
+	free(pool_set);
+	return 0;
+}
+
+/* Ownership of pool is handed over to pool set on success. */
+int rseq_percpu_pool_set_add_pool(struct rseq_percpu_pool_set *pool_set, struct rseq_percpu_pool *pool)
+{
+	size_t item_order = pool->item_order;
+	int ret = 0;
+
+	pthread_mutex_lock(&pool_set->lock);
+	if (pool_set->entries[item_order]) {
+		errno = EBUSY;
+		ret = -1;
+		goto end;
+	}
+	pool_set->entries[pool->item_order] = pool;
+end:
+	pthread_mutex_unlock(&pool_set->lock);
+	return ret;
+}
+
+static
+void *__rseq_percpu_pool_set_malloc(struct rseq_percpu_pool_set *pool_set, size_t len, bool zeroed)
+{
+	int order, min_order = POOL_SET_MIN_ENTRY;
+	struct rseq_percpu_pool *pool;
+	void *addr;
+
+again:
+	pthread_mutex_lock(&pool_set->lock);
+	/* First smallest present pool where @len fits. */
+	for (order = min_order; order < POOL_SET_NR_ENTRIES; order++) {
+		pool = pool_set->entries[order];
+
+		if (!pool)
+			continue;
+		if (pool->item_len >= len)
+			goto found;
+	}
+	pool = NULL;
+found:
+	pthread_mutex_unlock(&pool_set->lock);
+	if (pool) {
+		addr = __rseq_percpu_malloc(pool, zeroed);
+		if (addr == NULL && errno == ENOMEM) {
+			/*
+			 * If the allocation failed, try again with a
+			 * larger pool.
+			 */
+			min_order = order + 1;
+			goto again;
+		}
+	} else {
+		/* Not found. */
+		errno = ENOMEM;
+		addr = NULL;
+	}
+	return addr;
+}
+
+void *rseq_percpu_pool_set_malloc(struct rseq_percpu_pool_set *pool_set, size_t len)
+{
+	return __rseq_percpu_pool_set_malloc(pool_set, len, false);
+}
+
+void *rseq_percpu_pool_set_zmalloc(struct rseq_percpu_pool_set *pool_set, size_t len)
+{
+	return __rseq_percpu_pool_set_malloc(pool_set, len, true);
+}