[Xen-devel] [PATCH] perf: Replace malloc with alloca in hot path

[Santosh Jodh <santosh.jodh@xxxxxxxxxx>]

Replace malloc with alloc in hot paths for improved performance.

Signed-off-by: Santosh Jodh <santosh.jodh@xxxxxxxxxx>

diff -r e2722b24dc09 -r 4952090d35e0 tools/libxc/xc_linux_osdep.c
--- a/tools/libxc/xc_linux_osdep.c      Thu Jan 26 17:43:31 2012 +0000
+++ b/tools/libxc/xc_linux_osdep.c      Mon Jan 30 11:02:32 2012 -0800
@@ -242,7 +242,7 @@ static void *linux_privcmd_map_foreign_b
          * IOCTL_PRIVCMD_MMAPBATCH_V2 is not supported - fall back to
          * IOCTL_PRIVCMD_MMAPBATCH.
          */
-        xen_pfn_t *pfn = malloc(num * sizeof(*pfn));
+        xen_pfn_t *pfn = alloca(num * sizeof(*pfn));
 
         if ( pfn )
         {
@@ -288,8 +288,6 @@ static void *linux_privcmd_map_foreign_b
                 break;
             }
 
-            free(pfn);
-
             if ( rc == -ENOENT && i == num )
                 rc = 0;
             else if ( rc )
@@ -524,7 +522,7 @@ static void *linux_gnttab_grant_map(xc_g
     if (flags & XC_GRANT_MAP_SINGLE_DOMAIN)
         domids_stride = 0;
 
-    map = malloc(sizeof(*map) +
+    map = alloca(sizeof(*map) +
                  (count - 1) * sizeof(struct ioctl_gntdev_map_grant_ref));
     if ( map == NULL )
         return NULL;
@@ -598,7 +596,6 @@ static void *linux_gnttab_grant_map(xc_g
     }
 
  out:
-    free(map);
 
     return addr;
 }

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