Move the global safepoint to one page before static space

[sbcl.git] / src / compiler / generic / parms.lisp

diff --git a/src/compiler/generic/parms.lisp b/src/compiler/generic/parms.lisp
index b49671f..19af15f 100644 (file)
--- a/src/compiler/generic/parms.lisp
+++ b/src/compiler/generic/parms.lisp
@@ -33,6 +33,80 @@
                       (32 (expt 2 29))
                       (64 (expt 2 30))))))))))
 
+#!+gencgc
+;; Define START/END constants for GENCGC spaces.
+;; Assumptions:
+;;     We only need very small read-only and static spaces, because
+;;     gencgc does not purify any more.  We can count on being able to
+;;     allocate them with roughly the same size, and next to each other.
+;;
+;;     There is one page of unmapped buffer between them for good measure.
+;;
+;;     The linkage table (if enabled) can be treated the same way.
+;;
+;;     Dynamic space traditionally sits elsewhere, so has its own
+;;     parameter.  But if not specified, it is allocated right after
+;;     the other spaces (used on Windows/x86).
+;;
+;;     The safepoint page (if enabled) is to be allocated immediately
+;;     prior to static page.  For x86(-64) this would not matter, because
+;;     they can only reference it using an absolute fixup anyway, but
+;;     for RISC platforms we can (and must) do better.
+;;
+;;     The safepoint page needs to be small enough that the offset from
+;;     static space is immediate, e.g. >= -2^12 for SPARC.  #x1000 works
+;;     for almost all platforms, but is too small to make VirtualProtect
+;;     happy -- hence the need for an extra `alignment' configuration
+;;     option below, which parms.lisp can set to #x10000 on Windows.
+;;
+;; Cosmetic problem:
+;;
+;;     In the interest of readability, &KEY would be much nicer than
+;;     &OPTIONAL.  But is it possible to use keyword arguments to
+;;     DEF!MACRO?
+;;
+(def!macro !gencgc-space-setup
+    (small-spaces-start
+     &optional dynamic-space-start*
+               default-dynamic-space-size
+               ;; Smallest os_validate()able alignment; used as safepoint
+               ;; page size.  Default suitable for POSIX platforms.
+               (alignment            #x1000)
+               ;; traditional distance between spaces -- including the margin:
+               (small-space-spread #x100000)
+               ;; traditional margin between spaces
+               (margin-size          #x1000))
+  (let* ((spaces '(read-only static #!+linkage-table linkage-table))
+         (ptr small-spaces-start)
+         safepoint-address
+         (small-space-forms
+          (loop for (space next-space) on spaces appending
+                (let* ((next-start (+ ptr small-space-spread))
+                       (end next-start))
+                  (when (eq next-space 'static)
+                    ;; margin becomes safepoint page; substract margin again.
+                    (decf end alignment)
+                    (setf safepoint-address end))
+                  (prog1
+                      `((def!constant ,(symbolicate space "-SPACE-START")
+                            ,ptr)
+                        (def!constant ,(symbolicate space "-SPACE-END")
+                            ,(- end margin-size)))
+                    (setf ptr next-start)))))
+         (safepoint-page-forms
+          (list #!+sb-safepoint
+                `(def!constant gc-safepoint-page-addr ,safepoint-address)))
+         (dynamic-space-start* (or dynamic-space-start* ptr))
+         (optional-dynamic-space-end
+          (when default-dynamic-space-size
+            (list (+ dynamic-space-start* default-dynamic-space-size)))))
+    `(progn
+       ,@safepoint-page-forms
+       ,@small-space-forms
+       (def!constant dynamic-space-start ,dynamic-space-start*)
+       (def!constant dynamic-space-end (!configure-dynamic-space-end
+                                        ,@optional-dynamic-space-end)))))
+
 (defparameter *c-callable-static-symbols*
   '(sub-gc
     sb!kernel::post-gc