!95 memory:optimize "Memory Fragmentation"

Merge pull request !95 from 赵鹏元/master

src/main.cpp

@@ -17,8 +17,29 @@
 
 #include "anbox/daemon.h"
 #include "anbox/utils.h"
+#include <malloc.h>
 
 int main(int argc, char **argv) {
+  /*  Note: Nowadays, glibc uses a dynamic mmap threshold by
+      default.  The initial value of the threshold is 128*1024, but
+      when blocks larger than the current threshold and less than or
+      equal to DEFAULT_MMAP_THRESHOLD_MAX are freed, the threshold
+      is adjusted upward to the size of the freed block.  When
+      dynamic mmap thresholding is in effect, the threshold for
+      trimming the heap is also dynamically adjusted to be twice the
+      dynamic mmap threshold.  Dynamic adjustment of the mmap
+      threshold is disabled if any of the M_TRIM_THRESHOLD,
+      M_TOP_PAD, M_MMAP_THRESHOLD, or M_MMAP_MAX parameters is set. */
+
+  constexpr int KILO_BYTES = 1024;
+  constexpr int DEFAULT_THRESHOLD = 128 * KILO_BYTES;
+  constexpr int DEFAULT_TOP_PAD = 128 * KILO_BYTES;
+  constexpr int DEFAULT_MMAP_MAX = 64 * KILO_BYTES;
+  mallopt(M_ARENA_MAX, 2);
+  mallopt(M_MMAP_THRESHOLD, DEFAULT_THRESHOLD);
+  mallopt(M_TRIM_THRESHOLD, DEFAULT_THRESHOLD);
+  mallopt(M_TOP_PAD, DEFAULT_TOP_PAD);
+  mallopt(M_MMAP_MAX, DEFAULT_MMAP_MAX);
   anbox::Daemon daemon;
   return daemon.Run(anbox::utils::collect_arguments(argc, argv));
 }