0.pre8.4

[sbcl/lichteblau.git] / src / code / gc.lisp

;;;; garbage collection and allocation-related code

;;;; This software is part of the SBCL system. See the README file for
;;;; more information.
;;;;
;;;; This software is derived from the CMU CL system, which was
;;;; written at Carnegie Mellon University and released into the
;;;; public domain. The software is in the public domain and is
;;;; provided with absolutely no warranty. See the COPYING and CREDITS
;;;; files for more information.

(in-package "SB!KERNEL")
\f
;;;; DYNAMIC-USAGE and friends

(declaim (special sb!vm:*read-only-space-free-pointer*
                  sb!vm:*static-space-free-pointer*))

(eval-when (:compile-toplevel :execute)
  (sb!xc:defmacro def-c-var-frob (lisp-fun c-var-name)
    `(progn
       #!-sb-fluid (declaim (inline ,lisp-fun))
       (defun ,lisp-fun ()
         (sb!alien:extern-alien ,c-var-name (sb!alien:unsigned 32))))))

#!-gencgc
(progn
  ;; This is called once per PROFILEd function call, so it's worth a
  ;; little possible space cost to reduce its time cost.
  #!-sb-fluid
  (declaim (inline current-dynamic-space-start))
  (def-c-var-frob current-dynamic-space-start "current_dynamic_space"))

#!-sb-fluid
(declaim (inline dynamic-usage)) ; to reduce PROFILEd call overhead
#!+gencgc
(def-c-var-frob dynamic-usage "bytes_allocated")
#!-gencgc
(defun dynamic-usage ()
  (the (unsigned-byte 32)
       (- (sb!sys:sap-int (sb!c::dynamic-space-free-pointer))
          (current-dynamic-space-start))))

(defun static-space-usage ()
  (- (* sb!vm:*static-space-free-pointer* sb!vm:n-word-bytes)
     sb!vm:static-space-start))

(defun read-only-space-usage ()
  (- (* sb!vm::*read-only-space-free-pointer* sb!vm:n-word-bytes)
     sb!vm:read-only-space-start))

(defun control-stack-usage ()
  #!-stack-grows-downward-not-upward
  (- (sb!sys:sap-int (sb!c::control-stack-pointer-sap))
     sb!vm:control-stack-start)
  #!+stack-grows-downward-not-upward
  (- sb!vm:control-stack-end
     (sb!sys:sap-int (sb!c::control-stack-pointer-sap))))

(defun binding-stack-usage ()
  (- (sb!sys:sap-int (sb!c::binding-stack-pointer-sap))
     sb!vm:binding-stack-start))
\f
;;;; ROOM

(defun room-minimal-info ()
  (format t "Dynamic space usage is:   ~10:D bytes.~%" (dynamic-usage))
  (format t "Read-only space usage is: ~10:D bytes.~%" (read-only-space-usage))
  (format t "Static space usage is:    ~10:D bytes.~%" (static-space-usage))
  (format t "Control stack usage is:   ~10:D bytes.~%" (control-stack-usage))
  (format t "Binding stack usage is:   ~10:D bytes.~%" (binding-stack-usage))
  (format t "Garbage collection is currently ~:[enabled~;DISABLED~].~%"
          (> *gc-inhibit* 0)))

(defun room-intermediate-info ()
  (room-minimal-info)
  (sb!vm:memory-usage :count-spaces '(:dynamic)
                      :print-spaces t
                      :cutoff 0.05f0
                      :print-summary nil))

(defun room-maximal-info ()
  (room-minimal-info)
  (sb!vm:memory-usage :count-spaces '(:static :dynamic))
  (sb!vm:instance-usage :dynamic :top-n 10)
  (sb!vm:instance-usage :static :top-n 10))

(defun room (&optional (verbosity :default))
  #!+sb-doc
  "Print to *STANDARD-OUTPUT* information about the state of internal
  storage and its management. The optional argument controls the
  verbosity of output. If it is T, ROOM prints out a maximal amount of
  information. If it is NIL, ROOM prints out a minimal amount of
  information. If it is :DEFAULT or it is not supplied, ROOM prints out
  an intermediate amount of information."
  (fresh-line)
  (ecase verbosity
    ((t)
     (room-maximal-info))
    ((nil)
     (room-minimal-info))
    (:default
     (room-intermediate-info)))
  (values))
\f
;;;; GET-BYTES-CONSED

;;; the total number of bytes freed so far (including any freeing
;;; which goes on in PURIFY)
;;;
;;; (We save this so that we can calculate the total number of bytes
;;; ever allocated by adding this to the number of bytes currently
;;; allocated and never freed.)
(declaim (type unsigned-byte *n-bytes-freed-or-purified*))
(defvar *n-bytes-freed-or-purified* 0)
(push (lambda ()
        (setf *n-bytes-freed-or-purified* 0))
      ;; KLUDGE: It's probably not quite safely right either to do
      ;; this in *BEFORE-SAVE-INITIALIZATIONS* (since consing, or even
      ;; worse, something which depended on (GET-BYTES-CONSED), might
      ;; happen after that) or in *AFTER-SAVE-INITIALIZATIONS*. But
      ;; it's probably not a big problem, and there seems to be no
      ;; other obvious time to do it. -- WHN 2001-07-30
      *after-save-initializations*)

(declaim (ftype (function () unsigned-byte) get-bytes-consed))
(defun get-bytes-consed ()
  #!+sb-doc
  "Return the number of bytes consed since the program began. Typically
this result will be a consed bignum, so if you have an application (e.g.
profiling) which can't tolerate the overhead of consing bignums, you'll
probably want either to hack in at a lower level (as the code in the
SB-PROFILE package does), or to design a more microefficient interface
and submit it as a patch."
  (+ (dynamic-usage)
     *n-bytes-freed-or-purified*))
\f
;;;; variables and constants

;;; the minimum amount of dynamic space which must be consed before a
;;; GC will be triggered
;;;
;;; Unlike CMU CL, we don't export this variable. (There's no need to,
;;; since our BYTES-CONSED-BETWEEN-GCS function is SETFable.)
(defvar *bytes-consed-between-gcs*
  #!+gencgc (* 4 (expt 10 6))
  ;; Stop-and-copy GC is really really slow when used too often. CSR
  ;; reported that even on his old 64 Mb SPARC, 20 Mb is much faster
  ;; than 4 Mb when rebuilding SBCL ca. 0.7.1. For modern machines
  ;; with >> 128 Mb memory, the optimum could be significantly more
  ;; than this, but at least 20 Mb should be better than 4 Mb.
  #!-gencgc (* 20 (expt 10 6)))
(declaim (type index *bytes-consed-between-gcs*))

;;;; GC hooks

(defvar *before-gc-hooks* nil ; actually initialized in cold init
  #!+sb-doc
  "A list of functions that are called before garbage collection occurs.
  The functions should take no arguments.")

(defvar *after-gc-hooks* nil ; actually initialized in cold init
  #!+sb-doc
  "A list of functions that are called after garbage collection occurs.
  The functions should take no arguments.")

(defvar *gc-notify-stream* nil ; (actually initialized in cold init)
  #!+sb-doc
  "When non-NIL, this must be a STREAM; and the functions bound to
  *GC-NOTIFY-BEFORE* and *GC-NOTIFY-AFTER* are called with the
  STREAM value before and after a garbage collection occurs
  respectively.")

(defvar *gc-run-time* 0
  #!+sb-doc
  "the total CPU time spent doing garbage collection (as reported by
   GET-INTERNAL-RUN-TIME)")
(declaim (type index *gc-run-time*))

;;; a limit to help catch programs which allocate too much memory,
;;; since a hard heap overflow is so hard to recover from
;;;
;;; FIXME: Like *GC-TRIGGER*, this variable (1) should probably be
;;; denominated in a larger unit than bytes and (2) should probably be
;;; renamed so that it's clear from the name what unit it's
;;; denominated in.
(declaim (type (or unsigned-byte null) *soft-heap-limit*))
(defvar *soft-heap-limit*
  ;; As long as *GC-TRIGGER* is DECLAIMed as INDEX, we know that
  ;; MOST-POSITIVE-FIXNUM is a hard limit on how much memory can be
  ;; allocated. (Not necessarily *the* hard limit, which is fairly
  ;; likely something like a Unix per-process limit that we don't know
  ;; about, but a hard limit anyway.) And this gives us a reasonable
  ;; conservative default for the soft limit...
  (- most-positive-fixnum
     *bytes-consed-between-gcs*))

;;;; The following specials are used to control when garbage
;;;; collection occurs.

;;; When the dynamic usage increases beyond this amount, the system
;;; notes that a garbage collection needs to occur by setting
;;; *NEED-TO-COLLECT-GARBAGE* to T. It starts out as NIL meaning
;;; nobody has figured out what it should be yet.
;;;
;;; FIXME: *GC-TRIGGER* seems to be denominated in bytes, not words.
;;; And limiting it to INDEX is fairly reasonable in order to avoid
;;; bignum arithmetic on every allocation, and to minimize the need
;;; for thought about weird gotchas of the GC-control mechanism itself
;;; consing as it operates. But as of sbcl-0.7.5, 512Mbytes of memory
;;; costs $54.95 at Fry's in Dallas but cheap consumer 64-bit machines
;;; are still over the horizon, so gratuitously limiting our heap size
;;; to FIXNUM bytes seems fairly stupid. It'd be reasonable to
;;; (1) allow arbitrary UNSIGNED-BYTE values of *GC-TRIGGER*, or
;;; (2) redenominate this variable in words instead of bytes, postponing
;;;     the problem to heaps which exceed 50% of the machine's address
;;;     space, or even
;;; (3) redemoninate this variable in CONS-sized two-word units,
;;;     allowing it to cover the entire memory space at the price of
;;;     possible loss of clarity.
;;; (And whatever is done, it'd also be good to rename the variable so
;;; that it's clear what unit it's denominated in.)
(declaim (type (or index null) *gc-trigger*))
(defvar *gc-trigger* nil)

;;; When >0, inhibits garbage collection.
(defvar *gc-inhibit*) ; initialized in cold init

;;; This flag is used to prevent recursive entry into the garbage
;;; collector.
(defvar *already-maybe-gcing*) ; initialized in cold init

;;; When T, indicates that the dynamic usage has exceeded the value
;;; *GC-TRIGGER*.
(defvar *need-to-collect-garbage* nil) ; initialized in cold init
\f
(defun default-gc-notify-before (notify-stream bytes-in-use)
  (declare (type stream notify-stream))
  (format
   notify-stream
   "~&; GC is beginning with ~:D bytes in use at internal runtime ~:D.~%"
   bytes-in-use
   (get-internal-run-time))
  (finish-output notify-stream))
(defparameter *gc-notify-before* #'default-gc-notify-before
  #!+sb-doc
  "The function bound to this variable is invoked before GC'ing (unless
  *GC-NOTIFY-STREAM* is NIL) with the value of *GC-NOTIFY-STREAM* and
  current amount of dynamic usage (in bytes). It should notify the
  user that the system is going to GC.")

(defun default-gc-notify-after (notify-stream
                                bytes-retained
                                bytes-freed
                                new-trigger)
  (declare (type stream notify-stream))
  (format notify-stream
          "~&; GC has finished with ~:D bytes in use (~:D bytes freed)~@
           ; at internal runtime ~:D. The new GC trigger is ~:D bytes.~%"
          bytes-retained
          bytes-freed
          (get-internal-run-time)
          new-trigger)
  (finish-output notify-stream))
(defparameter *gc-notify-after* #'default-gc-notify-after
  #!+sb-doc
  "The function bound to this variable is invoked after GC'ing with the
value of *GC-NOTIFY-STREAM*, the amount of dynamic usage (in bytes) now
free, the number of bytes freed by the GC, and the new GC trigger
threshold; or if *GC-NOTIFY-STREAM* is NIL, it's not invoked. The
function should notify the user that the system has finished GC'ing.")
\f
;;;; internal GC

(sb!alien:define-alien-routine collect-garbage sb!alien:int
  (#!+gencgc last-gen #!-gencgc ignore sb!alien:int))

(sb!alien:define-alien-routine set-auto-gc-trigger sb!alien:void
  (dynamic-usage sb!alien:unsigned-long))

(sb!alien:define-alien-routine clear-auto-gc-trigger sb!alien:void)

;;; This variable contains the function that does the real GC. This is
;;; for low-level GC experimentation. Do not touch it if you do not
;;; know what you are doing.
(defvar *internal-gc* #'collect-garbage)
\f
;;;; SUB-GC

;;; This is used to carefully invoke hooks.
(eval-when (:compile-toplevel :execute)
  (sb!xc:defmacro carefully-funcall (function &rest args)
    `(handler-case (funcall ,function ,@args)
       (error (cond)
              (warn "(FUNCALL ~S~{ ~S~}) lost:~%~A" ',function ',args cond)
              nil))))

;;; SUB-GC decides when and if to do a garbage collection. The FORCE-P
;;; flags controls whether a GC should occur even if the dynamic usage
;;; is not greater than *GC-TRIGGER*.
;;;
;;; For GENCGC all generations < GEN will be GC'ed.

;;; XXX need (1) some kind of locking to ensure that only one thread
;;; at a time is trying to GC, (2) to look at all these specials and
;;; work out how much of this "do we really need to GC now?" stuff is
;;; actually necessary: I think we actually end up GCing every time we
;;; hit this code

(defun sub-gc (&key force-p (gen 0))
  (/show0 "entering SUB-GC")
  (unless *already-maybe-gcing*
    (let* ((*already-maybe-gcing* t)
           (start-time (get-internal-run-time))
           (pre-gc-dynamic-usage (dynamic-usage))
           ;; Currently we only check *SOFT-HEAP-LIMIT* at GC time,
           ;; not for every allocation. That makes it cheap to do,
           ;; even if it is a little ugly.
           (soft-heap-limit-exceeded? (and *soft-heap-limit*
                                           (> pre-gc-dynamic-usage
                                              *soft-heap-limit*)))
           (*soft-heap-limit* (if soft-heap-limit-exceeded?
                                  (+ pre-gc-dynamic-usage
                                     *bytes-consed-between-gcs*)
                                  *soft-heap-limit*)))
      (when soft-heap-limit-exceeded?
        (cerror "Continue with GC."
                "soft heap limit exceeded (temporary new limit=~W)"
                *soft-heap-limit*))
      (when (and *gc-trigger* (> pre-gc-dynamic-usage *gc-trigger*))
        (setf *need-to-collect-garbage* t))
      (when (or force-p
                (and *need-to-collect-garbage* (zerop *gc-inhibit*)))
        ;; KLUDGE: Wow, we really mask interrupts all the time we're
        ;; collecting garbage? That seems like a long time.. -- WHN 19991129
        (without-interrupts
         ;; FIXME: We probably shouldn't do this evil thing to
         ;; *STANDARD-OUTPUT* in a binding which is wrapped around
         ;; calls to user-settable GC hook functions.
          (let ((*standard-output* *terminal-io*))
            (when *gc-notify-stream*
              (if (streamp *gc-notify-stream*)
                  (carefully-funcall *gc-notify-before*
                                     *gc-notify-stream*
                                     pre-gc-dynamic-usage)
                  (warn
                   "*GC-NOTIFY-STREAM* is set, but not a STREAM -- ignored.")))
            (dolist (hook *before-gc-hooks*)
              (carefully-funcall hook))
            (when *gc-trigger*
              (clear-auto-gc-trigger))
            (let* (;; We do DYNAMIC-USAGE once more here in order to
                   ;; get a more accurate measurement of the space
                   ;; actually freed, since the messing around, e.g.
                   ;; GC-notify stuff, since the DYNAMIC-USAGE which
                   ;; triggered GC could've done a fair amount of
                   ;; consing.)
                   (pre-internal-gc-dynamic-usage (dynamic-usage))
                   (ignore-me (funcall *internal-gc* gen))
                   (post-gc-dynamic-usage (dynamic-usage))
                   (n-bytes-freed (- pre-internal-gc-dynamic-usage
                                     post-gc-dynamic-usage))
                   ;; In sbcl-0.6.12.39, the raw N-BYTES-FREED from
                   ;; GENCGC could sometimes be substantially negative
                   ;; (e.g. -5872). I haven't looked into what causes
                   ;; that, but I suspect it has to do with
                   ;; fluctuating inefficiency in the way that the
                   ;; GENCGC packs things into page boundaries.
                   ;; Bumping the raw result up to 0 is a little ugly,
                   ;; but shouldn't be a problem, and it's even
                   ;; possible to sort of justify it: the packing
                   ;; inefficiency which has caused (DYNAMIC-USAGE) to
                   ;; grow is effectively consing, or at least
                   ;; overhead of consing, so it's sort of correct to
                   ;; add it to the running total of consing. ("Man
                   ;; isn't a rational animal, he's a rationalizing
                   ;; animal.":-) -- WHN 2001-06-23
                   (eff-n-bytes-freed (max 0 n-bytes-freed)))
              (declare (ignore ignore-me))
              (/show0 "got (DYNAMIC-USAGE) and EFF-N-BYTES-FREED")
              (incf *n-bytes-freed-or-purified*
                    eff-n-bytes-freed)
              (/show0 "clearing *NEED-TO-COLLECT-GARBAGE*")
              (setf *need-to-collect-garbage* nil)
              (/show0 "calculating NEW-GC-TRIGGER")
              (let ((new-gc-trigger (+ post-gc-dynamic-usage
                                       *bytes-consed-between-gcs*)))
                (/show0 "setting *GC-TRIGGER*")
                (setf *gc-trigger* new-gc-trigger))
              (/show0 "calling SET-AUTO-GC-TRIGGER")
              (set-auto-gc-trigger *gc-trigger*)
              (dolist (hook *after-gc-hooks*)
                (/show0 "doing a hook from *AFTER-GC--HOOKS*")
                ;; FIXME: This hook should be called with the same
                ;; kind of information as *GC-NOTIFY-AFTER*. In
                ;; particular, it would be nice for the hook function
                ;; to be able to adjust *GC-TRIGGER* intelligently to
                ;; e.g. 108% of total memory usage.
                (carefully-funcall hook))
              (when *gc-notify-stream*
                (if (streamp *gc-notify-stream*)
                    (carefully-funcall *gc-notify-after*
                                       *gc-notify-stream*
                                       post-gc-dynamic-usage
                                       eff-n-bytes-freed
                                       *gc-trigger*)
                    (warn
                     "*GC-NOTIFY-STREAM* is set, but not a stream -- ignored.")))))
          (scrub-control-stack)))       ;XXX again?  we did this from C ...
      (incf *gc-run-time* (- (get-internal-run-time)
                             start-time))))
  ;; FIXME: should probably return (VALUES), here and in RETURN-FROM
  nil)

;;; This routine is called by the allocation miscops to decide whether
;;; a GC should occur. The argument, OBJECT, is the newly allocated
;;; object which must be returned to the caller.
(defun maybe-gc (&optional object)
  (sub-gc)
  object)

;;; This is the user-advertised garbage collection function.
(defun gc (&key (gen 0) (full nil) &allow-other-keys)
  #!+(and sb-doc gencgc)
  "Initiate a garbage collection. GEN controls the number of generations
  to garbage collect."
  #!+(and sb-doc (not gencgc))
  "Initiate a garbage collection. GEN may be provided for compatibility with
  generational garbage collectors, but is ignored in this implementation."
  (sub-gc :force-p t :gen (if full 6 gen)))

\f
;;;; auxiliary functions

(defun bytes-consed-between-gcs ()
  #!+sb-doc
  "Return the amount of memory that will be allocated before the next garbage
   collection is initiated. This can be set with SETF."
  *bytes-consed-between-gcs*)
(defun (setf bytes-consed-between-gcs) (val)
  ;; FIXME: Shouldn't this (and the DECLAIM for the underlying variable)
  ;; be for a strictly positive number type, e.g.
  ;; (AND (INTEGER 1) FIXNUM)?
  (declare (type index val))
  (let ((old *bytes-consed-between-gcs*))
    (setf *bytes-consed-between-gcs* val)
    (when *gc-trigger*
      (setf *gc-trigger* (+ *gc-trigger* (- val old)))
      (cond ((<= (dynamic-usage) *gc-trigger*)
             (clear-auto-gc-trigger)
             (set-auto-gc-trigger *gc-trigger*))
            (t
             ;; FIXME: If SCRUB-CONTROL-STACK is required here, why
             ;; isn't it built into SUB-GC? And *is* it required here?
             (sb!sys:scrub-control-stack)
             (sub-gc)))))
  val)

(defun gc-on ()
  #!+sb-doc
  "Enable the garbage collector."
  (setq *gc-inhibit* 0)
  (when *need-to-collect-garbage*
    (sub-gc))
  nil)

(defun gc-off ()
  #!+sb-doc
  "Disable the garbage collector."
  (setq *gc-inhibit* 1)
  nil)
\f
;;;; initialization stuff

(defun gc-reinit ()
  (when *gc-trigger*
    (if (< *gc-trigger* (dynamic-usage))
        (sub-gc)
        (set-auto-gc-trigger *gc-trigger*))))