Implement `Process.warmup`

[Feature #18885]

For now, the optimizations performed are:

  - Run a major GC
  - Compact the heap
  - Promote all surviving objects to oldgen

Other optimizations may follow.

1 files changed, 34 insertions, 0 deletions

diff --git a/process.c b/process.c
index daf3456bfd..9605036c64 100644
--- a/process.c
+++ b/process.c
@@ -115,6 +115,7 @@ int initgroups(const char *, rb_gid_t);
 #include "ruby/thread.h"
 #include "ruby/util.h"
 #include "vm_core.h"
+#include "vm_sync.h"
 #include "ruby/ractor.h"
 
 /* define system APIs */
@@ -8510,6 +8511,37 @@ static VALUE rb_mProcUID;
 static VALUE rb_mProcGID;
 static VALUE rb_mProcID_Syscall;
 
+/*
+ *  call-seq:
+ *     Process.warmup    -> true
+ *
+ *  Notify the Ruby virtual machine that the boot sequence is finished,
+ *  and that now is a good time to optimize the application. This is useful
+ *  for long running applications.
+ *
+ *  This method is expected to be called at the end of the application boot.
+ *  If the application is deployed using a pre-forking model, +Process.warmup+
+ *  should be called in the original process before the first fork.
+ *
+ *  The actual optimizations performed are entirely implementation specific
+ *  and may change in the future without notice.
+ *
+ *  On CRuby, +Process.warmup+:
+ *
+ *  * Perform a major GC.
+ *  * Compacts the heap.
+ *  * Promotes all surviving objects to the old generation.
+ */
+
+static VALUE
+proc_warmup(VALUE _)
+{
+    RB_VM_LOCK_ENTER();
+    rb_gc_prepare_heap();
+    RB_VM_LOCK_LEAVE();
+    return Qtrue;
+}
+
 
 /*
  * Document-module: Process
@@ -8627,6 +8659,8 @@ InitVM_process(void)
     rb_define_module_function(rb_mProcess, "getpriority", proc_getpriority, 2);
     rb_define_module_function(rb_mProcess, "setpriority", proc_setpriority, 3);
 
+    rb_define_module_function(rb_mProcess, "warmup", proc_warmup, 0);
+
 #ifdef HAVE_GETPRIORITY
     /* see Process.setpriority */
     rb_define_const(rb_mProcess, "PRIO_PROCESS", INT2FIX(PRIO_PROCESS));