Guardedalloc: Implement atomic peak memory update

Updating maximum requires a bit of a cycle which usually does 1 iteration only,
sometimes needs a bit more but seems there's no speed regressions.

For now the code is commented out. This way it's easier for others to verify
there's no speed regressions.

Reviewers: campbellbarton

Differential Revision: https://developer.blender.org/D626

2 files changed, 29 insertions, 12 deletions

diff --git a/intern/guardedalloc/intern/mallocn_intern.h b/intern/guardedalloc/intern/mallocn_intern.h
index 523d1786b97..7da74f7cc4c 100644
--- a/intern/guardedalloc/intern/mallocn_intern.h
+++ b/intern/guardedalloc/intern/mallocn_intern.h
@@ -103,6 +103,13 @@
 #  include <stdlib.h>
 #endif
 
+/* visual studio 2012 does not define inline for C */
+#ifdef _MSC_VER
+#  define MEM_INLINE static __inline
+#else
+#  define MEM_INLINE static inline
+#endif
+
 #define IS_POW2(a) (((a) & ((a) - 1)) == 0)
 
 /* Extra padding which needs to be applied on MemHead to make it aligned. */
diff --git a/intern/guardedalloc/intern/mallocn_lockfree_impl.c b/intern/guardedalloc/intern/mallocn_lockfree_impl.c
index ffb23702601..c0f6aeeaa9d 100644
--- a/intern/guardedalloc/intern/mallocn_lockfree_impl.c
+++ b/intern/guardedalloc/intern/mallocn_lockfree_impl.c
@@ -70,6 +70,23 @@ enum {
 #define MEMHEAD_IS_MMAP(memhead) ((memhead)->len & (size_t) MEMHEAD_MMAP_FLAG)
 #define MEMHEAD_IS_ALIGNED(memhead) ((memhead)->len & (size_t) MEMHEAD_ALIGN_FLAG)
 
+/* Uncomment this to have proper peak counter. */
+//#define USE_ATOMIC_MAX
+
+MEM_INLINE void update_maximum(size_t *maximum_value, size_t value)
+{
+#ifdef USE_ATOMIC_MAX
+	size_t prev_value = *maximum_value;
+	while (prev_value < value) {
+		if (atomic_cas_z(maximum_value, prev_value, value) != prev_value) {
+			break;
+		}
+	}
+#else
+	*maximum_value = value > *maximum_value ? value : *maximum_value;
+#endif
+}
+
 #ifdef __GNUC__
 __attribute__ ((format(printf, 1, 2)))
 #endif
@@ -264,9 +281,7 @@ void *MEM_lockfree_callocN(size_t len, const char *str)
 		memh->len = len;
 		atomic_add_u(&totblock, 1);
 		atomic_add_z(&mem_in_use, len);
-
-		/* TODO(sergey): Not strictly speaking thread-safe. */
-		peak_mem = mem_in_use > peak_mem ? mem_in_use : peak_mem;
+		update_maximum(&peak_mem, mem_in_use);
 
 		return PTR_FROM_MEMHEAD(memh);
 	}
@@ -291,9 +306,7 @@ void *MEM_lockfree_mallocN(size_t len, const char *str)
 		memh->len = len;
 		atomic_add_u(&totblock, 1);
 		atomic_add_z(&mem_in_use, len);
-
-		/* TODO(sergey): Not strictly speaking thread-safe. */
-		peak_mem = mem_in_use > peak_mem ? mem_in_use : peak_mem;
+		update_maximum(&peak_mem, mem_in_use);
 
 		return PTR_FROM_MEMHEAD(memh);
 	}
@@ -342,9 +355,7 @@ void *MEM_lockfree_mallocN_aligned(size_t len, size_t alignment, const char *str
 		memh->alignment = (short) alignment;
 		atomic_add_u(&totblock, 1);
 		atomic_add_z(&mem_in_use, len);
-
-		/* TODO(sergey): Not strictly speaking thread-safe. */
-		peak_mem = mem_in_use > peak_mem ? mem_in_use : peak_mem;
+		update_maximum(&peak_mem, mem_in_use);
 
 		return PTR_FROM_MEMHEAD(memh);
 	}
@@ -381,9 +392,8 @@ void *MEM_lockfree_mapallocN(size_t len, const char *str)
 		atomic_add_z(&mem_in_use, len);
 		atomic_add_z(&mmap_in_use, len);
 
-		/* TODO(sergey): Not strictly speaking thread-safe. */
-		peak_mem = mem_in_use > peak_mem ? mem_in_use : peak_mem;
-		peak_mem = mmap_in_use > peak_mem ? mmap_in_use : peak_mem;
+		update_maximum(&peak_mem, mem_in_use);
+		update_maximum(&peak_mem, mmap_in_use);
 
 		return PTR_FROM_MEMHEAD(memh);
 	}