Don't use mmap below a certain size threshold

gst/tmpfile/gstfddepay.c

@@ -37,6 +37,7 @@
 #include "gstfddepay.h"
 #include "wire-protocol.h"
 #include "../gstnetcontrolmessagemeta.h"
+#include "gsttmpfileallocator.h"
 
 #include <gst/gst.h>
 #include <gst/base/gstbasetransform.h>
@@ -201,6 +202,14 @@ gst_fddepay_set_clock (GstElement * element, GstClock * clock)
       clock);
 }
 
+static int
+steal_fd (int *p_fd)
+{
+  int fd = *p_fd;
+  *p_fd = -1;
+  return fd;
+}
+
 static GstFlowReturn
 gst_fddepay_transform_ip (GstBaseTransform * trans, GstBuffer * buf)
 {
@@ -263,11 +272,34 @@ gst_fddepay_transform_ip (GstBaseTransform * trans, GstBuffer * buf)
         fd, (ssize_t) statbuf.st_size, msg.offset, msg.size);
     goto error;
   }
-  fdmem = gst_fd_allocator_alloc (fddepay->fd_allocator, fd,
-      msg.offset + msg.size, GST_FD_MEMORY_FLAG_KEEP_MAPPED);
-  fd = -1;
-  gst_memory_resize (fdmem, msg.offset, msg.size);
-  GST_MINI_OBJECT_FLAG_SET (fdmem, GST_MEMORY_FLAG_READONLY);
+  if (msg.size >= tmpfile_mmap_threshold ()) {
+    fdmem = gst_fd_allocator_alloc (fddepay->fd_allocator, steal_fd(&fd),
+        msg.offset + msg.size, GST_FD_MEMORY_FLAG_KEEP_MAPPED);
+    gst_memory_resize (fdmem, msg.offset, msg.size);
+    GST_MINI_OBJECT_FLAG_SET (fdmem, GST_MEMORY_FLAG_READONLY);
+  } else {
+    g_autofree char *buf = g_malloc (msg.size);
+    size_t off = 0;
+    while (off < msg.size) {
+      ssize_t res = pread (fd, buf + off, msg.size - off, msg.offset + off);
+      if (res < 0) {
+        if (errno == EINTR)
+          continue;
+        GST_WARNING_OBJECT (fddepay, "fddepay: Reading from fd %i failed: %s",
+            fd, g_strerror(errno));
+        goto error;
+      } else if (res == 0) {
+        GST_WARNING_OBJECT (fddepay, "fddepay: Reading from fd %i failed: "
+            "Unexpected EOS", fd);
+        goto error;
+      } else {
+        off += res;
+      }
+    }
+    fdmem = gst_memory_new_wrapped (0, g_steal_pointer(&buf), msg.size,
+        msg.offset, msg.size, buf, g_free);
+    close (steal_fd(&fd));
+  }
 
   gst_buffer_remove_all_memory (buf);
   gst_buffer_remove_meta (buf,

gst/tmpfile/gsttmpfileallocator.c

@@ -30,6 +30,7 @@
 #include <unistd.h>
 
 #define PAGE_ALIGN 4095
+#define DEFAULT_MMAP_THRESHOLD (128 * 1024)
 
 GST_DEBUG_CATEGORY_STATIC (gst_tmpfileallocator_debug);
 #define GST_CAT_DEFAULT gst_tmpfileallocator_debug
@@ -42,6 +43,7 @@ typedef struct
   GstAllocator *fd_allocator;
   uint32_t frame_count;
   uint32_t pid;
+  gsize mmap_threshold;
 } GstTmpFileAllocator;
 
 typedef struct
@@ -81,6 +83,24 @@ gst_tmpfile_allocator_init (GstTmpFileAllocator * alloc)
   alloc->fd_allocator = gst_fd_allocator_new ();
   alloc->frame_count = 0;
   alloc->pid = getpid();
+  alloc->mmap_threshold = tmpfile_mmap_threshold ();
+}
+
+gsize tmpfile_mmap_threshold (void)
+{
+  static gsize mmap_threshold = 0;
+  if (g_once_init_enter (&mmap_threshold))
+  {
+    const char* st = getenv("TMPFILE_MMAP_THRESHOLD");
+    if (st == NULL)
+      st = "";
+    gsize mt = atol(st);
+    if (mt == 0)
+      mt = DEFAULT_MMAP_THRESHOLD;
+
+    g_once_init_leave (&mmap_threshold, mt);
+  }
+  return mmap_threshold;
 }
 
 static void
@@ -157,6 +177,12 @@ gst_tmpfile_allocator_alloc (GstAllocator * allocator, gsize size,
       pad (size + pad (params->prefix, params->align) + params->padding,
       PAGE_ALIGN);
 
+  if (maxsize < alloc->mmap_threshold) {
+    /* Below a certain size the cost of mmap outweighs the cost of copying the
+     * data */
+    return gst_allocator_alloc (NULL, size, params);
+  }
+
   if (alloc->fd_allocator == NULL)
     return NULL;
 

gst/tmpfile/gsttmpfileallocator.h

@@ -30,5 +30,7 @@ GstAllocator* gst_tmpfile_allocator_new (void);
 GstMemory * gst_tmpfile_allocator_copy_alloc (GstAllocator * alloc,
     const void * data, size_t n);
 
+gsize tmpfile_mmap_threshold (void);
+
 G_END_DECLS
 #endif