From: Kevin Day <thekevinday@gmail.com>
Date: Sun, 12 Dec 2021 05:59:06 +0000 (-0600)
Subject: Update: Improve performance by removing redundant memset().
X-Git-Tag: 0.5.7~42
X-Git-Url: https://git.kevux.org/?a=commitdiff_plain;h=c567ef798e17b0c91b4eff17157140c175b71f84;p=fll

Update: Improve performance by removing redundant memset().

The calloc() program is supposed to guarantee 0 filled data.
Either the libc or the kernel know how to optimize this automatically using numerous tricks based on architecture or lack thereof.
This makes calloc() potentially faster than malloc()+memset().

Calling calloc()+memset() is just ridiculous.
Remove the calls to memset() that follow a calloc() call.
This is guaranteed to be a performance increase (but how much? I didn't bother trying to find out).

Cleanup some comments.
---

diff --git a/level_0/f_memory/c/memory.c b/level_0/f_memory/c/memory.c
index 1d03bda..9bc3121 100644
--- a/level_0/f_memory/c/memory.c
+++ b/level_0/f_memory/c/memory.c
@@ -26,7 +26,7 @@ extern "C" {
       if (!pointer) return F_status_set_error(F_parameter);
     #endif // _di_level_0_parameter_checking_
 
-    // prevent double-frees.
+    // Prevent double-frees.
     if (!*pointer || !size) {
       return F_data_not;
     }
@@ -39,7 +39,7 @@ extern "C" {
 
     free(*pointer);
 
-    // it has been deallocated, so reset the pointer.
+    // It has been deallocated, so reset the pointer.
     *pointer = 0;
 
     return F_none;
@@ -53,7 +53,7 @@ extern "C" {
       if (!pointer) return F_status_set_error(F_parameter);
     #endif // _di_level_0_parameter_checking_
 
-    // prevent double-frees.
+    // Prevent double-frees.
     if (!*pointer) {
       return F_data_not;
     }
@@ -66,7 +66,7 @@ extern "C" {
 
     free(*pointer);
 
-    // it has been deallocated, so reset the pointer.
+    // It has been deallocated, so reset the pointer.
     *pointer = 0;
 
     return F_none;
@@ -85,16 +85,9 @@ extern "C" {
       return F_data_not;
     }
 
-    // Some people use malloc(size * length) to produce the same results.
-    // This has been observed to sometimes causes an increase in L1/L2 cache misses (0.02% L1 increase, 0.01% L2 increase).
     *pointer = calloc(length, size);
 
     if (*pointer) {
-
-      // uint8_t * is of a data size size of 1, casting it to uint8_t should result in a single-length increment.
-      // this is done to avoid problems with (void *) having arithmetic issues.
-      memset(((uint8_t *) *pointer), 0, size * length);
-
       return F_none;
     }
 
@@ -110,7 +103,7 @@ extern "C" {
       if (!pointer) return F_status_set_error(F_parameter);
     #endif // _di_level_0_parameter_checking_
 
-    // prevent double-allocations.
+    // Prevent double-allocations.
     if (*pointer || !length) {
       return F_data_not;
     }
@@ -139,8 +132,8 @@ extern "C" {
       }
     #endif // _f_memory_USE_posix_memalign_
 
-    // uint8_t * is of a data size size of 1, casting it to uint8_t should result in a single-length increment.
-    // this is done to avoid problems with (void *) having arithmetic issues.
+    // uint8_t * is of a data size of 1, casting it to uint8_t should result in a single-length increment.
+    // This is done to avoid problems with (void *) having arithmetic issues.
     memset(((uint8_t *) *pointer), 0, length);
 
     return F_none;
diff --git a/level_0/f_memory/c/private-memory.c b/level_0/f_memory/c/private-memory.c
index 271021a..8b5761c 100644
--- a/level_0/f_memory/c/private-memory.c
+++ b/level_0/f_memory/c/private-memory.c
@@ -17,7 +17,7 @@ extern "C" {
         if (length_new < length_old) {
 
           // uint8_t * is of a data size size of 1, casting it to uint8_t should result in a single-length increment.
-          // this is done to avoid problems with (void *) having arithmetic issues.
+          // This is done to avoid problems with (void *) having arithmetic issues.
           memset(((uint8_t *) *pointer) + length_new, 0, type_size * (length_old - length_new));
         }
       }
@@ -29,7 +29,7 @@ extern "C" {
           if (length_new > length_old) {
 
             // uint8_t * is of a data size size of 1, casting it to bool should result in a single-length increment.
-            // this is done to avoid problems with (void *) having arithmetic issues.
+            // This is done to avoid problems with (void *) having arithmetic issues.
             memset(((uint8_t *) new_pointer) + (type_size * length_old), 0, type_size * (length_new - length_old));
           }
 
@@ -43,7 +43,7 @@ extern "C" {
       else {
         free(*pointer);
 
-        // assure that the pointer is always 0 after deallocation.
+        // Assure that the pointer is always 0 after deallocation.
         *pointer = 0;
 
         return F_none;
@@ -53,8 +53,6 @@ extern "C" {
       *pointer = calloc(type_size, length_new);
 
       if (*pointer) {
-        memset(*pointer, 0, type_size * length_new);
-
         return F_none;
       }
     }
@@ -81,7 +79,7 @@ extern "C" {
           if (length_new > length_old) {
 
             // uint8_t * is of a data size size of 1, casting it to bool should result in a single-length increment.
-            // this is done to avoid problems with (void *) having arithmetic issues.
+            // This is done to avoid problems with (void *) having arithmetic issues.
             memset(((uint8_t *) new_pointer) + (type_size * length_old), 0, type_size * (length_new - length_old));
           }
 
@@ -95,7 +93,7 @@ extern "C" {
       else {
         free(*pointer);
 
-        // assure that the pointer is always 0 after deallocation.
+        // Assure that the pointer is always 0 after deallocation.
         *pointer = 0;
 
         return F_none;
@@ -105,8 +103,6 @@ extern "C" {
       *pointer = calloc(type_size, length_new);
 
       if (*pointer) {
-        memset(*pointer, 0, type_size * length_new);
-
         return F_none;
       }
     }