1 ;;;; garbage collection and allocation-related code
3 ;;;; This software is part of the SBCL system. See the README file for
6 ;;;; This software is derived from the CMU CL system, which was
7 ;;;; written at Carnegie Mellon University and released into the
8 ;;;; public domain. The software is in the public domain and is
9 ;;;; provided with absolutely no warranty. See the COPYING and CREDITS
10 ;;;; files for more information.
12 (in-package "SB!KERNEL")
14 ;;;; DYNAMIC-USAGE and friends
16 (declaim (special sb!vm:*read-only-space-free-pointer*
17 sb!vm:*static-space-free-pointer*))
19 (eval-when (:compile-toplevel :execute)
20 (sb!xc:defmacro def-c-var-frob (lisp-fun c-var-name)
22 #!-sb-fluid (declaim (inline ,lisp-fun))
24 (sb!alien:extern-alien ,c-var-name (sb!alien:unsigned 32))))))
28 ;; This is called once per PROFILEd function call, so it's worth a
29 ;; little possible space cost to reduce its time cost.
31 (declaim (inline current-dynamic-space-start))
32 (def-c-var-frob current-dynamic-space-start "current_dynamic_space"))
35 (declaim (inline dynamic-usage)) ; to reduce PROFILEd call overhead
37 (def-c-var-frob dynamic-usage "bytes_allocated")
39 (defun dynamic-usage ()
40 (the (unsigned-byte 32)
41 (- (sb!sys:sap-int (sb!c::dynamic-space-free-pointer))
42 (current-dynamic-space-start))))
44 (defun static-space-usage ()
45 (- (* sb!vm:*static-space-free-pointer* sb!vm:n-word-bytes)
46 sb!vm:static-space-start))
48 (defun read-only-space-usage ()
49 (- (* sb!vm::*read-only-space-free-pointer* sb!vm:n-word-bytes)
50 sb!vm:read-only-space-start))
52 (defun control-stack-usage ()
53 #!-stack-grows-downward-not-upward
54 (- (sb!sys:sap-int (sb!c::control-stack-pointer-sap))
55 (sb!vm:fixnumize sb!vm::*control-stack-start*))
56 #!+stack-grows-downward-not-upward
57 (- (sb!vm:fixnumize sb!vm::*control-stack-end*)
58 (sb!sys:sap-int (sb!c::control-stack-pointer-sap))))
60 (defun binding-stack-usage ()
61 (- (sb!sys:sap-int (sb!c::binding-stack-pointer-sap))
62 (sb!vm:fixnumize sb!vm::*binding-stack-start*)))
66 (defun room-minimal-info ()
67 (format t "Dynamic space usage is: ~10:D bytes.~%" (dynamic-usage))
68 (format t "Read-only space usage is: ~10:D bytes.~%" (read-only-space-usage))
69 (format t "Static space usage is: ~10:D bytes.~%" (static-space-usage))
70 (format t "Control stack usage is: ~10:D bytes.~%" (control-stack-usage))
71 (format t "Binding stack usage is: ~10:D bytes.~%" (binding-stack-usage))
74 "Control and binding stack usage is for the current thread only.~%")
75 (format t "Garbage collection is currently ~:[enabled~;DISABLED~].~%"
78 (defun room-intermediate-info ()
80 (sb!vm:memory-usage :count-spaces '(:dynamic)
85 (defun room-maximal-info ()
87 (sb!vm:memory-usage :count-spaces '(:static :dynamic))
88 (sb!vm:instance-usage :dynamic :top-n 10)
89 (sb!vm:instance-usage :static :top-n 10))
91 (defun room (&optional (verbosity :default))
93 "Print to *STANDARD-OUTPUT* information about the state of internal
94 storage and its management. The optional argument controls the
95 verbosity of output. If it is T, ROOM prints out a maximal amount of
96 information. If it is NIL, ROOM prints out a minimal amount of
97 information. If it is :DEFAULT or it is not supplied, ROOM prints out
98 an intermediate amount of information."
106 (room-intermediate-info)))
109 ;;;; GET-BYTES-CONSED
111 ;;; the total number of bytes freed so far (including any freeing
112 ;;; which goes on in PURIFY)
114 ;;; (We save this so that we can calculate the total number of bytes
115 ;;; ever allocated by adding this to the number of bytes currently
116 ;;; allocated and never freed.)
117 (declaim (type unsigned-byte *n-bytes-freed-or-purified*))
118 (defvar *n-bytes-freed-or-purified* 0)
120 (setf *n-bytes-freed-or-purified* 0))
121 ;; KLUDGE: It's probably not quite safely right either to do
122 ;; this in *BEFORE-SAVE-INITIALIZATIONS* (since consing, or even
123 ;; worse, something which depended on (GET-BYTES-CONSED), might
124 ;; happen after that) or in *AFTER-SAVE-INITIALIZATIONS*. But
125 ;; it's probably not a big problem, and there seems to be no
126 ;; other obvious time to do it. -- WHN 2001-07-30
127 *after-save-initializations*)
129 (declaim (ftype (function () unsigned-byte) get-bytes-consed))
130 (defun get-bytes-consed ()
132 "Return the number of bytes consed since the program began. Typically
133 this result will be a consed bignum, so if you have an application (e.g.
134 profiling) which can't tolerate the overhead of consing bignums, you'll
135 probably want either to hack in at a lower level (as the code in the
136 SB-PROFILE package does), or to design a more microefficient interface
137 and submit it as a patch."
139 *n-bytes-freed-or-purified*))
141 ;;;; variables and constants
143 ;;; the minimum amount of dynamic space which must be consed before a
144 ;;; GC will be triggered
146 ;;; Unlike CMU CL, we don't export this variable. (There's no need to,
147 ;;; since our BYTES-CONSED-BETWEEN-GCS function is SETFable.)
148 (defvar *bytes-consed-between-gcs*
149 #!+gencgc (* 4 (expt 10 6))
150 ;; Stop-and-copy GC is really really slow when used too often. CSR
151 ;; reported that even on his old 64 Mb SPARC, 20 Mb is much faster
152 ;; than 4 Mb when rebuilding SBCL ca. 0.7.1. For modern machines
153 ;; with >> 128 Mb memory, the optimum could be significantly more
154 ;; than this, but at least 20 Mb should be better than 4 Mb.
155 #!-gencgc (* 20 (expt 10 6)))
156 (declaim (type index *bytes-consed-between-gcs*))
160 (defvar *before-gc-hooks* nil ; actually initialized in cold init
162 "A list of functions that are called before garbage collection occurs.
163 The functions should take no arguments.")
165 (defvar *after-gc-hooks* nil ; actually initialized in cold init
167 "A list of functions that are called after garbage collection occurs.
168 The functions should take no arguments.")
170 (defvar *gc-notify-stream* nil ; (actually initialized in cold init)
172 "When non-NIL, this must be a STREAM; and the functions bound to
173 *GC-NOTIFY-BEFORE* and *GC-NOTIFY-AFTER* are called with the
174 STREAM value before and after a garbage collection occurs
177 (defvar *gc-run-time* 0
179 "the total CPU time spent doing garbage collection (as reported by
180 GET-INTERNAL-RUN-TIME)")
181 (declaim (type index *gc-run-time*))
183 ;;; a limit to help catch programs which allocate too much memory,
184 ;;; since a hard heap overflow is so hard to recover from
186 ;;; FIXME: Like *GC-TRIGGER*, this variable (1) should probably be
187 ;;; denominated in a larger unit than bytes and (2) should probably be
188 ;;; renamed so that it's clear from the name what unit it's
190 (declaim (type (or unsigned-byte null) *soft-heap-limit*))
191 (defvar *soft-heap-limit*
192 ;; As long as *GC-TRIGGER* is DECLAIMed as INDEX, we know that
193 ;; MOST-POSITIVE-FIXNUM is a hard limit on how much memory can be
194 ;; allocated. (Not necessarily *the* hard limit, which is fairly
195 ;; likely something like a Unix per-process limit that we don't know
196 ;; about, but a hard limit anyway.) And this gives us a reasonable
197 ;; conservative default for the soft limit...
198 (- most-positive-fixnum
199 *bytes-consed-between-gcs*))
201 ;;;; The following specials are used to control when garbage
202 ;;;; collection occurs.
204 ;;; When the dynamic usage increases beyond this amount, the system
205 ;;; notes that a garbage collection needs to occur by setting
206 ;;; *NEED-TO-COLLECT-GARBAGE* to T. It starts out as NIL meaning
207 ;;; nobody has figured out what it should be yet.
209 ;;; FIXME: *GC-TRIGGER* seems to be denominated in bytes, not words.
210 ;;; And limiting it to INDEX is fairly reasonable in order to avoid
211 ;;; bignum arithmetic on every allocation, and to minimize the need
212 ;;; for thought about weird gotchas of the GC-control mechanism itself
213 ;;; consing as it operates. But as of sbcl-0.7.5, 512Mbytes of memory
214 ;;; costs $54.95 at Fry's in Dallas but cheap consumer 64-bit machines
215 ;;; are still over the horizon, so gratuitously limiting our heap size
216 ;;; to FIXNUM bytes seems fairly stupid. It'd be reasonable to
217 ;;; (1) allow arbitrary UNSIGNED-BYTE values of *GC-TRIGGER*, or
218 ;;; (2) redenominate this variable in words instead of bytes, postponing
219 ;;; the problem to heaps which exceed 50% of the machine's address
221 ;;; (3) redemoninate this variable in CONS-sized two-word units,
222 ;;; allowing it to cover the entire memory space at the price of
223 ;;; possible loss of clarity.
224 ;;; (And whatever is done, it'd also be good to rename the variable so
225 ;;; that it's clear what unit it's denominated in.)
226 (declaim (type (or index null) *gc-trigger*))
227 (defvar *gc-trigger* nil)
229 ;;; When >0, inhibits garbage collection.
230 (defvar *gc-inhibit*) ; initialized in cold init
232 ;;; This flag is used to prevent recursive entry into the garbage
234 (defvar *already-maybe-gcing*) ; initialized in cold init
236 ;;; When T, indicates that the dynamic usage has exceeded the value
238 (defvar *need-to-collect-garbage* nil) ; initialized in cold init
240 (defun default-gc-notify-before (notify-stream bytes-in-use)
241 (declare (type stream notify-stream))
244 "~&; GC is beginning with ~:D bytes in use at internal runtime ~:D.~%"
246 (get-internal-run-time))
247 (finish-output notify-stream))
248 (defparameter *gc-notify-before* #'default-gc-notify-before
250 "The function bound to this variable is invoked before GC'ing (unless
251 *GC-NOTIFY-STREAM* is NIL) with the value of *GC-NOTIFY-STREAM* and
252 current amount of dynamic usage (in bytes). It should notify the
253 user that the system is going to GC.")
255 (defun default-gc-notify-after (notify-stream
259 (declare (type stream notify-stream))
260 (format notify-stream
261 "~&; GC has finished with ~:D bytes in use (~:D bytes freed)~@
262 ; at internal runtime ~:D. The new GC trigger is ~:D bytes.~%"
265 (get-internal-run-time)
267 (finish-output notify-stream))
268 (defparameter *gc-notify-after* #'default-gc-notify-after
270 "The function bound to this variable is invoked after GC'ing with the
271 value of *GC-NOTIFY-STREAM*, the amount of dynamic usage (in bytes) now
272 free, the number of bytes freed by the GC, and the new GC trigger
273 threshold; or if *GC-NOTIFY-STREAM* is NIL, it's not invoked. The
274 function should notify the user that the system has finished GC'ing.")
278 (sb!alien:define-alien-routine collect-garbage sb!alien:int
279 (#!+gencgc last-gen #!-gencgc ignore sb!alien:int))
281 (sb!alien:define-alien-routine set-auto-gc-trigger sb!alien:void
282 (dynamic-usage sb!alien:unsigned-long))
284 (sb!alien:define-alien-routine clear-auto-gc-trigger sb!alien:void)
287 (def-c-var-frob gc-thread-pid "gc_thread_pid")
289 (defun other-thread-collect-garbage (gen)
290 (setf (sb!alien:extern-alien "maybe_gc_pending" (sb!alien:unsigned 32))
292 (sb!unix:unix-kill (gc-thread-pid) :SIGALRM))
294 ;;; This variable contains the function that does the real GC. This is
295 ;;; for low-level GC experimentation. Do not touch it if you do not
296 ;;; know what you are doing.
297 (defvar *internal-gc*
298 #!+sb-thread #'other-thread-collect-garbage
299 #!-sb-thread #'collect-garbage)
304 ;;; This is used to carefully invoke hooks.
305 (eval-when (:compile-toplevel :execute)
306 (sb!xc:defmacro carefully-funcall (function &rest args)
307 `(handler-case (funcall ,function ,@args)
309 (warn "(FUNCALL ~S~{ ~S~}) lost:~%~A" ',function ',args cond)
312 ;;; SUB-GC decides when and if to do a garbage collection. The FORCE-P
313 ;;; flags controls whether a GC should occur even if the dynamic usage
314 ;;; is not greater than *GC-TRIGGER*.
316 ;;; For GENCGC all generations < GEN will be GC'ed.
318 ;;; XXX need (1) some kind of locking to ensure that only one thread
319 ;;; at a time is trying to GC, (2) to look at all these specials and
320 ;;; work out how much of this "do we really need to GC now?" stuff is
321 ;;; actually necessary: I think we actually end up GCing every time we
324 (defun sub-gc (&key force-p (gen 0))
325 (/show0 "entering SUB-GC")
326 (unless *already-maybe-gcing*
327 (let* ((*already-maybe-gcing* t)
328 (start-time (get-internal-run-time))
329 (pre-gc-dynamic-usage (dynamic-usage))
330 ;; Currently we only check *SOFT-HEAP-LIMIT* at GC time,
331 ;; not for every allocation. That makes it cheap to do,
332 ;; even if it is a little ugly.
333 (soft-heap-limit-exceeded? (and *soft-heap-limit*
334 (> pre-gc-dynamic-usage
336 (*soft-heap-limit* (if soft-heap-limit-exceeded?
337 (+ pre-gc-dynamic-usage
338 *bytes-consed-between-gcs*)
340 (when soft-heap-limit-exceeded?
341 (cerror "Continue with GC."
342 "soft heap limit exceeded (temporary new limit=~W)"
344 (when (and *gc-trigger* (> pre-gc-dynamic-usage *gc-trigger*))
345 (setf *need-to-collect-garbage* t))
347 (and *need-to-collect-garbage* (zerop *gc-inhibit*)))
348 ;; KLUDGE: Wow, we really mask interrupts all the time we're
349 ;; collecting garbage? That seems like a long time.. -- WHN 19991129
351 ;; FIXME: We probably shouldn't do this evil thing to
352 ;; *STANDARD-OUTPUT* in a binding which is wrapped around
353 ;; calls to user-settable GC hook functions.
354 (let ((*standard-output* *terminal-io*))
355 (when *gc-notify-stream*
356 (if (streamp *gc-notify-stream*)
357 (carefully-funcall *gc-notify-before*
359 pre-gc-dynamic-usage)
361 "*GC-NOTIFY-STREAM* is set, but not a STREAM -- ignored.")))
362 (dolist (hook *before-gc-hooks*)
363 (carefully-funcall hook))
365 (clear-auto-gc-trigger))
366 (let* (;; We do DYNAMIC-USAGE once more here in order to
367 ;; get a more accurate measurement of the space
368 ;; actually freed, since the messing around, e.g.
369 ;; GC-notify stuff, since the DYNAMIC-USAGE which
370 ;; triggered GC could've done a fair amount of
372 (pre-internal-gc-dynamic-usage (dynamic-usage))
373 (ignore-me (funcall *internal-gc* gen))
374 (post-gc-dynamic-usage (dynamic-usage))
375 (n-bytes-freed (- pre-internal-gc-dynamic-usage
376 post-gc-dynamic-usage))
377 ;; In sbcl-0.6.12.39, the raw N-BYTES-FREED from
378 ;; GENCGC could sometimes be substantially negative
379 ;; (e.g. -5872). I haven't looked into what causes
380 ;; that, but I suspect it has to do with
381 ;; fluctuating inefficiency in the way that the
382 ;; GENCGC packs things into page boundaries.
383 ;; Bumping the raw result up to 0 is a little ugly,
384 ;; but shouldn't be a problem, and it's even
385 ;; possible to sort of justify it: the packing
386 ;; inefficiency which has caused (DYNAMIC-USAGE) to
387 ;; grow is effectively consing, or at least
388 ;; overhead of consing, so it's sort of correct to
389 ;; add it to the running total of consing. ("Man
390 ;; isn't a rational animal, he's a rationalizing
391 ;; animal.":-) -- WHN 2001-06-23
392 (eff-n-bytes-freed (max 0 n-bytes-freed)))
393 (declare (ignore ignore-me))
394 (/show0 "got (DYNAMIC-USAGE) and EFF-N-BYTES-FREED")
395 (incf *n-bytes-freed-or-purified*
397 (/show0 "clearing *NEED-TO-COLLECT-GARBAGE*")
398 (setf *need-to-collect-garbage* nil)
399 (/show0 "calculating NEW-GC-TRIGGER")
400 (let ((new-gc-trigger (+ post-gc-dynamic-usage
401 *bytes-consed-between-gcs*)))
402 (/show0 "setting *GC-TRIGGER*")
403 (setf *gc-trigger* new-gc-trigger))
404 (/show0 "calling SET-AUTO-GC-TRIGGER")
405 (set-auto-gc-trigger *gc-trigger*)
406 (dolist (hook *after-gc-hooks*)
407 (/show0 "doing a hook from *AFTER-GC--HOOKS*")
408 ;; FIXME: This hook should be called with the same
409 ;; kind of information as *GC-NOTIFY-AFTER*. In
410 ;; particular, it would be nice for the hook function
411 ;; to be able to adjust *GC-TRIGGER* intelligently to
412 ;; e.g. 108% of total memory usage.
413 (carefully-funcall hook))
414 (when *gc-notify-stream*
415 (if (streamp *gc-notify-stream*)
416 (carefully-funcall *gc-notify-after*
418 post-gc-dynamic-usage
422 "*GC-NOTIFY-STREAM* is set, but not a stream -- ignored.")))))
423 (scrub-control-stack))) ;XXX again? we did this from C ...
424 (incf *gc-run-time* (- (get-internal-run-time)
426 ;; FIXME: should probably return (VALUES), here and in RETURN-FROM
429 ;;; This routine is called by the allocation miscops to decide whether
430 ;;; a GC should occur. The argument, OBJECT, is the newly allocated
431 ;;; object which must be returned to the caller.
432 (defun maybe-gc (&optional object)
436 ;;; This is the user-advertised garbage collection function.
437 (defun gc (&key (gen 0) (full nil) &allow-other-keys)
438 #!+(and sb-doc gencgc)
439 "Initiate a garbage collection. GEN controls the number of generations
441 #!+(and sb-doc (not gencgc))
442 "Initiate a garbage collection. GEN may be provided for compatibility with
443 generational garbage collectors, but is ignored in this implementation."
444 (sub-gc :force-p t :gen (if full 6 gen)))
447 ;;;; auxiliary functions
449 (defun bytes-consed-between-gcs ()
451 "Return the amount of memory that will be allocated before the next garbage
452 collection is initiated. This can be set with SETF."
453 *bytes-consed-between-gcs*)
454 (defun (setf bytes-consed-between-gcs) (val)
455 ;; FIXME: Shouldn't this (and the DECLAIM for the underlying variable)
456 ;; be for a strictly positive number type, e.g.
457 ;; (AND (INTEGER 1) FIXNUM)?
458 (declare (type index val))
459 (let ((old *bytes-consed-between-gcs*))
460 (setf *bytes-consed-between-gcs* val)
462 (setf *gc-trigger* (+ *gc-trigger* (- val old)))
463 (cond ((<= (dynamic-usage) *gc-trigger*)
464 (clear-auto-gc-trigger)
465 (set-auto-gc-trigger *gc-trigger*))
467 ;; FIXME: If SCRUB-CONTROL-STACK is required here, why
468 ;; isn't it built into SUB-GC? And *is* it required here?
469 (sb!sys:scrub-control-stack)
475 "Enable the garbage collector."
476 (setq *gc-inhibit* 0)
477 (when *need-to-collect-garbage*
483 "Disable the garbage collector."
484 (setq *gc-inhibit* 1)
487 ;;;; initialization stuff
491 (if (< *gc-trigger* (dynamic-usage))
493 (set-auto-gc-trigger *gc-trigger*))))