1 files changed, 138 insertions, 88 deletions

diff --git a/sysdep/unix/alloc.c b/sysdep/unix/alloc.c
index 4ae1a9db..47cd4624 100644
--- a/sysdep/unix/alloc.c
+++ b/sysdep/unix/alloc.c
@@ -8,130 +8,180 @@
 
 #include "nest/bird.h"
 #include "lib/resource.h"
+#include "lib/lists.h"
+#include "lib/event.h"
+#include "lib/rcu.h"
 
+#include <errno.h>
 #include <stdlib.h>
 #include <unistd.h>
-#include <stdatomic.h>
-#include <errno.h>
 
 #ifdef HAVE_MMAP
 #include <sys/mman.h>
 #endif
 
 long page_size = 0;
-_Bool alloc_multipage = 0;
 
-static _Atomic int global_page_list_not_empty;
-static list global_page_list;
-static _Atomic int global_page_spinlock;
+#ifdef HAVE_MMAP
+#define KEEP_PAGES_MAX	256
+#define KEEP_PAGES_MIN	8
 
-#define	GLOBAL_PAGE_SPIN_LOCK	for (int v = 0; !atomic_compare_exchange_weak_explicit(&global_page_spinlock, &v, 1, memory_order_acq_rel, memory_order_acquire); v = 0)
-#define GLOBAL_PAGE_SPIN_UNLOCK	do { int v = 1; ASSERT_DIE(atomic_compare_exchange_strong_explicit(&global_page_spinlock, &v, 0, memory_order_acq_rel, memory_order_acquire)); } while (0)
+STATIC_ASSERT(KEEP_PAGES_MIN * 4 < KEEP_PAGES_MAX);
 
-#ifdef HAVE_MMAP
 static _Bool use_fake = 0;
+static _Bool initialized = 0;
+
+#if DEBUGGING
+struct free_page {
+  node unused[42];
+  struct free_page * _Atomic next;
+};
 #else
-static _Bool use_fake = 1;
+struct free_page {
+  struct free_page * _Atomic next;
+};
 #endif
 
-void resource_sys_init(void)
+static struct free_page * _Atomic page_stack = NULL;
+
+static void page_cleanup(void *);
+static event page_cleanup_event = { .hook = page_cleanup, };
+#define SCHEDULE_CLEANUP  do if (initialized && !shutting_down) ev_send(&global_event_list, &page_cleanup_event); while (0)
+
+_Atomic int pages_kept = 0;
+
+static void *
+alloc_sys_page(void)
 {
-#ifdef HAVE_MMAP
-  init_list(&global_page_list);
+  void *ptr = mmap(NULL, page_size, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
 
-  if (!(page_size = sysconf(_SC_PAGESIZE)))
-    die("System page size must be non-zero");
+  if (ptr == MAP_FAILED)
+    bug("mmap(%lu) failed: %m", page_size);
 
-  if ((u64_popcount(page_size) > 1) || (page_size > 16384))
+  return ptr;
+}
+
+extern int shutting_down; /* Shutdown requested. */
+
+#else // ! HAVE_MMAP
+#define use_fake  1
 #endif
+
+void *
+alloc_page(void)
+{
+  if (use_fake)
   {
-    /* Too big or strange page, use the aligned allocator instead */
-    page_size = 4096;
-    use_fake = 1;
+    void *ptr = NULL;
+    int err = posix_memalign(&ptr, page_size, page_size);
+
+    if (err || !ptr)
+      bug("posix_memalign(%lu) failed", (long unsigned int) page_size);
+
+    return ptr;
   }
+
+#ifdef HAVE_MMAP
+  rcu_read_lock();
+  struct free_page *fp = atomic_load_explicit(&page_stack, memory_order_acquire);
+  while (fp && !atomic_compare_exchange_strong_explicit(
+	&page_stack, &fp, atomic_load_explicit(&fp->next, memory_order_acquire),
+	memory_order_acq_rel, memory_order_acquire))
+    ;
+  rcu_read_unlock();
+
+  if (!fp)
+    return alloc_sys_page();
+
+  if (atomic_fetch_sub_explicit(&pages_kept, 1, memory_order_relaxed) <= KEEP_PAGES_MIN)
+    SCHEDULE_CLEANUP;
+
+  return fp;
+#endif
 }
 
-void *
-alloc_sys_page(void)
+void
+free_page(void *ptr)
 {
-#ifdef HAVE_MMAP
-  if (!use_fake)
+  if (use_fake)
   {
-    if (atomic_load_explicit(&global_page_list_not_empty, memory_order_relaxed))
-    {
-      GLOBAL_PAGE_SPIN_LOCK;
-      if (!EMPTY_LIST(global_page_list))
-      {
-	node *ret = HEAD(global_page_list);
-	rem_node(ret);
-	if (EMPTY_LIST(global_page_list))
-	  atomic_store_explicit(&global_page_list_not_empty, 0, memory_order_relaxed);
-	GLOBAL_PAGE_SPIN_UNLOCK;
-	memset(ret, 0, sizeof(node));
-	return (void *) ret;
-      }
-      GLOBAL_PAGE_SPIN_UNLOCK;
-    }
-
-    if (alloc_multipage)
-    {
-      void *big = mmap(NULL, page_size * 2, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-      if (big == MAP_FAILED)
-	bug("mmap(%lu) failed: %m", page_size);
-
-      uintptr_t offset = ((uintptr_t) big) % page_size;
-      if (offset)
-      {
-	void *ret = big + page_size - offset;
-	munmap(big, page_size - offset);
-	munmap(ret + page_size, offset);
-	return ret;
-      }
-      else
-      {
-	munmap(big + page_size, page_size);
-	return big;
-      }
-    }
-
-    void *ret = mmap(NULL, page_size, PROT_WRITE | PROT_READ, MAP_PRIVATE | MAP_ANONYMOUS, -1, 0);
-    if (ret == MAP_FAILED)
-      bug("mmap(%lu) failed: %m", page_size);
-
-    return ret;
+    free(ptr);
+    return;
   }
-  else
+
+#ifdef HAVE_MMAP
+  rcu_read_lock();
+  struct free_page *fp = ptr;
+  struct free_page *next = atomic_load_explicit(&page_stack, memory_order_acquire);
+
+  do atomic_store_explicit(&fp->next, next, memory_order_release);
+  while (!atomic_compare_exchange_strong_explicit(
+	&page_stack, &next, fp,
+	memory_order_acq_rel, memory_order_acquire));
+  rcu_read_unlock();
+
+  if (atomic_fetch_add_explicit(&pages_kept, 1, memory_order_relaxed) >= KEEP_PAGES_MAX)
+    SCHEDULE_CLEANUP;
 #endif
+}
+
+#ifdef HAVE_MMAP
+static void
+page_cleanup(void *_ UNUSED)
+{
+  struct free_page *stack = atomic_exchange_explicit(&page_stack, NULL, memory_order_acq_rel);
+  if (!stack)
+    return;
+
+  synchronize_rcu();
+
+  do {
+    struct free_page *f = stack;
+    stack = atomic_load_explicit(&f->next, memory_order_acquire);
+
+    if (munmap(f, page_size) == 0)
+      continue;
+    else if (errno != ENOMEM)
+      bug("munmap(%p) failed: %m", f);
+    else
+      free_page(f);
+  }
+  while (stack && (atomic_fetch_sub_explicit(&pages_kept, 1, memory_order_relaxed) >= KEEP_PAGES_MAX / 2));
+
+  while (stack)
   {
-    void *ret = aligned_alloc(page_size, page_size);
-    if (!ret)
-      bug("aligned_alloc(%lu) failed", page_size);
-    return ret;
+    atomic_fetch_sub_explicit(&pages_kept, 1, memory_order_relaxed);
+
+    struct free_page *f = stack;
+    stack = atomic_load_explicit(&f->next, memory_order_acquire);
+    free_page(f);
   }
 }
+#endif
 
 void
-free_sys_page(void *ptr)
+resource_sys_init(void)
 {
 #ifdef HAVE_MMAP
-  if (!use_fake)
+  if (!(page_size = sysconf(_SC_PAGESIZE)))
+    die("System page size must be non-zero");
+
+  if (u64_popcount(page_size) == 1)
   {
-    if (munmap(ptr, page_size) < 0)
-#ifdef ENOMEM
-      if (errno == ENOMEM)
-      {
-	memset(ptr, 0, page_size);
-
-	GLOBAL_PAGE_SPIN_LOCK;
-	add_tail(&global_page_list, (node *) ptr);
-	atomic_store_explicit(&global_page_list_not_empty, 1, memory_order_relaxed);
-	GLOBAL_PAGE_SPIN_UNLOCK;
-      }
-      else
-#endif
-	bug("munmap(%p) failed: %m", ptr);
+
+    for (int i = 0; i < (KEEP_PAGES_MIN * 2); i++)
+      free_page(alloc_page());
+
+    page_cleanup(NULL);
+    initialized = 1;
+    return;
   }
-  else
+
+  /* Too big or strange page, use the aligned allocator instead */
+  log(L_WARN "Got strange memory page size (%lu), using the aligned allocator instead", page_size);
+  use_fake = 1;
 #endif
-    free(ptr);
+
+  page_size = 4096;
+  initialized = 1;
 }