Read GC parameters from environmentscratch/igc2

* src/igc.c (read_gens, read_pause_time, read_commit_limit): New.
(make_arena): Use them.

1 files changed, 97 insertions, 2 deletions

diff --git a/src/igc.c b/src/igc.c
index 55fd133b954..5ec0ebde854 100644
--- a/src/igc.c
+++ b/src/igc.c
@@ -4885,19 +4885,114 @@ really know what you are doing!  */)
   return Qnil;
 }
 
+/* Read GC generation settings from environment variable
+   EMACS_IGC_GENS. Value must be a string consisting of pairs SIZE
+   MORTALITY, where SIZE Is the size of the generation in KB, and
+   mortality is a floating-point number between 0 and 1. All numbers are
+   separated by spaces. Example:
+
+   export EMACS_IGC_GENS="256000 0.8 256000 0.6 256000 0.4 512000 0.2"
+
+   specifies to use 4 generations. The first three have a sizeof 256 MB,
+   with mortality 0.8, 0.6, and 0.4. The fourth generation has a size of
+   512 MB and a mortality of 0.2. */
+
+static bool
+read_gens (mps_gen_param_s **gens, int *ngens)
+{
+  const char *env = getenv ("EMACS_IGC_GENS");
+  if (env == NULL)
+    return false;
+  const char *end = env + strlen (env);
+  static struct mps_gen_param_s parms[10];
+  *ngens = 0;
+  *gens = parms;
+  for (int i = 0; i < ARRAYELTS (parms) && env < end; ++i)
+    {
+      int nchars;
+      if (sscanf (env, "%zu %lf%n", &parms[i].mps_capacity,
+                  &parms[i].mps_mortality, &nchars) == 2)
+        {
+          env += nchars;
+          ++*ngens;
+        }
+    }
+
+  return true;
+}
+
+/* Read GC maximum pause time from environment variable
+   EMACS_IGC_PAUSE_TIME. Value must be a floating point number
+   specifying the pause time in seconds. Example:
+
+   export EMACS_IGC_PAUSE_TIME=0.05
+
+   says to use 50ms maximum pause time. */
+
+static bool
+read_pause_time (double *time)
+{
+  const char *env = getenv ("EMACS_IGC_PAUSE_TIME");
+  if (env == NULL)
+    return false;
+  return sscanf (env, "%lf", time) == 1;
+}
+
+/* Read GC commit limit from environment variable
+   EMACS_IGC_COMMIT_LIMIT. Value must be an integer number specifying
+   the commit limit in bytes. Example:
+
+   export EMACS_IGC_COMMIT_LIMIT=1000000000
+
+   Do not use this, except for testing.  */
+
+static bool
+read_commit_limit (size_t *limit)
+{
+  const char *env = getenv ("EMACS_IGC_COMMIT_LIMIT");
+  if (env == NULL)
+    return false;
+  return sscanf (env, "%zu", limit) == 1;
+}
+
 static void
 make_arena (struct igc *gc)
 {
   mps_res_t res;
   MPS_ARGS_BEGIN (args)
   {
+    double pause_time;
+    if (read_pause_time (&pause_time))
+      MPS_ARGS_ADD (args, MPS_KEY_PAUSE_TIME, pause_time);
+
+    size_t commit_limit;
+    if (read_commit_limit (&commit_limit))
+      MPS_ARGS_ADD (args, MPS_KEY_COMMIT_LIMIT, commit_limit);
+
     res = mps_arena_create_k (&gc->arena, mps_arena_class_vm (), args);
   }
   MPS_ARGS_END (args);
   IGC_CHECK_RES (res);
 
-  mps_gen_param_s gens[] = { { 128000, 0.8 }, { 5 * 128000, 0.4 } };
-  res = mps_chain_create (&gc->chain, gc->arena, ARRAYELTS (gens), gens);
+  mps_gen_param_s *gens;
+  int ngens;
+  if (!read_gens (&gens, &ngens))
+    {
+      static mps_gen_param_s default_gens[] = { { 128000, 0.8 }, { 5 * 128000, 0.4 } };
+      gens = default_gens;
+      ngens = ARRAYELTS (default_gens);
+    }
+
+  if (getenv ("EMACS_IGC_VERBOSE"))
+    {
+      for (int i = 0; i < ngens; ++i)
+        fprintf (stderr, "gen %d: %zu %lf\n", i, gens[i].mps_capacity,
+                 gens[i].mps_mortality);
+      fprintf (stderr, "pause time %lf\n", mps_arena_pause_time (gc->arena));
+      fprintf (stderr, "commit limit %zu\n", mps_arena_commit_limit (gc->arena));
+    }
+
+  res = mps_chain_create (&gc->chain, gc->arena, ngens, gens);
   IGC_CHECK_RES (res);
 }