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 ()
86 ;; FIXME: SB!VM:INSTANCE-USAGE calls suppressed until bug 344 is fixed
87 (room-intermediate-info)
88 ;; old way, could be restored when bug 344 fixed:
89 ;;x (room-minimal-info)
90 ;;x (sb!vm:memory-usage :count-spaces '(:static :dynamic))
91 ;;x (sb!vm:instance-usage :dynamic :top-n 10)
92 ;;x (sb!vm:instance-usage :static :top-n 10)
95 (defun room (&optional (verbosity :default))
97 "Print to *STANDARD-OUTPUT* information about the state of internal
98 storage and its management. The optional argument controls the
99 verbosity of output. If it is T, ROOM prints out a maximal amount of
100 information. If it is NIL, ROOM prints out a minimal amount of
101 information. If it is :DEFAULT or it is not supplied, ROOM prints out
102 an intermediate amount of information."
110 (room-intermediate-info)))
113 ;;;; GET-BYTES-CONSED
115 ;;; the total number of bytes freed so far (including any freeing
116 ;;; which goes on in PURIFY)
118 ;;; (We save this so that we can calculate the total number of bytes
119 ;;; ever allocated by adding this to the number of bytes currently
120 ;;; allocated and never freed.)
121 (declaim (type unsigned-byte *n-bytes-freed-or-purified*))
122 (defvar *n-bytes-freed-or-purified* 0)
126 (setf *n-bytes-freed-or-purified* 0))
128 (declaim (ftype (function () unsigned-byte) get-bytes-consed))
129 (defun get-bytes-consed ()
131 "Return the number of bytes consed since the program began. Typically
132 this result will be a consed bignum, so if you have an application (e.g.
133 profiling) which can't tolerate the overhead of consing bignums, you'll
134 probably want either to hack in at a lower level (as the code in the
135 SB-PROFILE package does), or to design a more microefficient interface
136 and submit it as a patch."
138 *n-bytes-freed-or-purified*))
142 (defvar *after-gc-hooks* nil
143 "Called after each garbage collection. In a multithreaded
144 environment these hooks may run in any thread.")
146 ;;;; The following specials are used to control when garbage
147 ;;;; collection occurs.
149 ;;; When the dynamic usage increases beyond this amount, the system
150 ;;; notes that a garbage collection needs to occur by setting
151 ;;; *NEED-TO-COLLECT-GARBAGE* to T. It starts out as NIL meaning
152 ;;; nobody has figured out what it should be yet.
154 ;;; FIXME: *GC-TRIGGER* seems to be denominated in bytes, not words.
155 ;;; And limiting it to INDEX is fairly reasonable in order to avoid
156 ;;; bignum arithmetic on every allocation, and to minimize the need
157 ;;; for thought about weird gotchas of the GC-control mechanism itself
158 ;;; consing as it operates. But as of sbcl-0.7.5, 512Mbytes of memory
159 ;;; costs $54.95 at Fry's in Dallas but cheap consumer 64-bit machines
160 ;;; are still over the horizon, so gratuitously limiting our heap size
161 ;;; to FIXNUM bytes seems fairly stupid. It'd be reasonable to
162 ;;; (1) allow arbitrary UNSIGNED-BYTE values of *GC-TRIGGER*, or
163 ;;; (2) redenominate this variable in words instead of bytes, postponing
164 ;;; the problem to heaps which exceed 50% of the machine's address
166 ;;; (3) redemoninate this variable in CONS-sized two-word units,
167 ;;; allowing it to cover the entire memory space at the price of
168 ;;; possible loss of clarity.
169 ;;; (And whatever is done, it'd also be good to rename the variable so
170 ;;; that it's clear what unit it's denominated in.)
171 (declaim (type (or index null) *gc-trigger*))
172 (defvar *gc-trigger* nil)
174 ;;; When T, indicates that a GC should have happened but did not due to
176 (defvar *need-to-collect-garbage* nil) ; initialized in cold init
180 (sb!alien:define-alien-routine collect-garbage sb!alien:int
181 (#!+gencgc last-gen #!-gencgc ignore sb!alien:int))
185 (sb!alien:define-alien-routine gc-stop-the-world sb!alien:void)
186 (sb!alien:define-alien-routine gc-start-the-world sb!alien:void))
189 (defun gc-stop-the-world ())
190 (defun gc-start-the-world ()))
195 ;;; SUB-GC does a garbage collection. This is called from three places:
196 ;;; (1) The C runtime will call here when it detects that we've consed
197 ;;; enough to exceed the gc trigger threshold. This is done in
198 ;;; alloc() for gencgc or interrupt_maybe_gc() for cheneygc
199 ;;; (2) The user may request a collection using GC, below
200 ;;; (3) At the end of a WITHOUT-GCING section, we are called if
201 ;;; *NEED-TO-COLLECT-GARBAGE* is true
203 ;;; This is different from the behaviour in 0.7 and earlier: it no
204 ;;; longer decides whether to GC based on thresholds. If you call
205 ;;; SUB-GC you will definitely get a GC either now or when the
206 ;;; WITHOUT-GCING is over
208 ;;; For GENCGC all generations < GEN will be GC'ed.
210 (defvar *already-in-gc*
211 (sb!thread:make-mutex :name "GC lock") "ID of thread running SUB-GC")
213 (defun sub-gc (&key (gen 0))
214 (unless (eql (sb!thread:current-thread-id)
215 (sb!thread::mutex-value *already-in-gc*))
216 (setf *need-to-collect-garbage* t)
217 (when (zerop *gc-inhibit*)
218 (sb!thread:with-mutex (*already-in-gc*)
219 (let ((old-usage (dynamic-usage))
222 ;; We need to disable interrupts for GC, but we also want
223 ;; to run as little as possible without them.
226 (collect-garbage gen)
227 (setf *need-to-collect-garbage* nil
228 new-usage (dynamic-usage))
229 (gc-start-the-world))
230 ;; Interrupts re-enabled, but still inside the mutex.
231 ;; In a multithreaded environment the other threads will
232 ;; see *n-b-f-o-p* change a little late, but that's OK.
233 (let ((freed (- old-usage new-usage)))
234 ;; GENCGC occasionally reports negative here, but the
235 ;; current belief is that it is part of the normal order
236 ;; of things and not a bug.
238 (incf *n-bytes-freed-or-purified* freed)))
239 (sb!thread::reap-dead-threads)))
240 ;; Outside the mutex, these may cause another GC.
241 (run-pending-finalizers)
242 (dolist (hook *after-gc-hooks*)
246 (warn "Error calling after GC hook ~S:~% ~S" hook c)))))))
248 ;;; This is the user-advertised garbage collection function.
249 (defun gc (&key (gen 0) (full nil) &allow-other-keys)
250 #!+(and sb-doc gencgc)
251 "Initiate a garbage collection. GEN controls the number of generations
253 #!+(and sb-doc (not gencgc))
254 "Initiate a garbage collection. GEN may be provided for compatibility with
255 generational garbage collectors, but is ignored in this implementation."
256 (sub-gc :gen (if full 6 gen)))
258 (defun unsafe-clear-roots ()
259 ;; KLUDGE: Do things in an attempt to get rid of extra roots. Unsafe
260 ;; as having these cons more then we have space left leads to huge
262 (scrub-control-stack)
263 ;; FIXME: CTYPE-OF-CACHE-CLEAR isn't thread-safe.
265 (ctype-of-cache-clear))
268 ;;;; auxiliary functions
270 (defun bytes-consed-between-gcs ()
272 "Return the amount of memory that will be allocated before the next garbage
273 collection is initiated. This can be set with SETF."
274 (sb!alien:extern-alien "bytes_consed_between_gcs"
275 (sb!alien:unsigned 32)))
277 (defun (setf bytes-consed-between-gcs) (val)
278 (declare (type index val))
279 (setf (sb!alien:extern-alien "bytes_consed_between_gcs"
280 (sb!alien:unsigned 32))
283 ;;; FIXME: Aren't these utterly wrong if called inside WITHOUT-GCING?
284 ;;; Unless something that works there too can be deviced this fact
285 ;;; should be documented.
288 "Enable the garbage collector."
289 (setq *gc-inhibit* 0)
290 (when *need-to-collect-garbage*
296 "Disable the garbage collector."
297 (setq *gc-inhibit* 1)