mem: 优化 C 内存统计, 缓解多线程竞争导致的 skynet_malloc 性能下降 (#2083)

* mem: 优化 C 内存统计, 缓解多线程竞争导致的 skynet_malloc 性能下降

* rm unused SPMC_STEP_LG macro

---------

Co-authored-by: efve.zff <efve.zff@alibaba-inc.com>

skynet-src/mem_info.c

@@ -0,0 +1,59 @@
+#include <string.h>
+
+#include "mem_info.h"
+
+void
+meminfo_init(MemInfo *info) {
+    memset(info, 0, sizeof(*info));
+}
+
+void
+atomic_meminfo_init(AtomicMemInfo *info) {
+    ATOM_INIT(&info->alloc, 0);
+    ATOM_INIT(&info->alloc_count, 0);
+    ATOM_INIT(&info->free, 0);
+    ATOM_INIT(&info->free_count, 0);
+}
+
+void
+meminfo_alloc(MemInfo *info, size_t size) {
+    info->alloc += size;
+    ++info->alloc_count;
+}
+
+void
+atomic_meminfo_alloc(AtomicMemInfo *info, size_t size) {
+    ATOM_FADD(&info->alloc, size);
+    ATOM_FADD(&info->alloc_count, 1);
+}
+
+void
+meminfo_free(MemInfo *info, size_t size) {
+    info->free += size;
+    ++info->free_count;
+}
+
+void
+atomic_meminfo_free(AtomicMemInfo *info, size_t size) {
+    ATOM_FADD(&info->free, size);
+    ATOM_FADD(&info->free_count, 1);
+}
+
+void
+meminfo_merge(MemInfo *dest, const MemInfo *src) {
+    dest->alloc += src->alloc;
+    dest->alloc_count += src->alloc_count;
+    dest->free += src->free;
+    dest->free_count += src->free_count;
+}
+
+void
+atomic_meminfo_merge(MemInfo *dest, const AtomicMemInfo *src) {
+    MemInfo info;
+    // 先加载 free 后加载 alloc 避免大小错乱
+    info.free_count = ATOM_LOAD(&src->free_count);
+    info.free = ATOM_LOAD(&src->free);
+    info.alloc_count = ATOM_LOAD(&src->alloc_count);
+    info.alloc = ATOM_LOAD(&src->alloc);
+    meminfo_merge(dest, &info);
+}