3 * Tunable parameters and debugging switches.
5 * Copyright 2001-2003 Ximian, Inc
6 * Copyright 2003-2010 Novell, Inc.
7 * Copyright 2011 Xamarin Inc (http://www.xamarin.com)
8 * Copyright (C) 2012 Xamarin Inc
10 * Licensed under the MIT license. See LICENSE file in the project root for full license information.
12 #ifndef __MONO_SGENCONF_H__
13 #define __MONO_SGENCONF_H__
17 /*Basic defines and static tunables */
19 #if SIZEOF_VOID_P == 4
20 typedef guint32 mword;
22 typedef guint64 mword;
25 typedef mword SgenDescriptor;
26 #define SGEN_DESCRIPTOR_NULL 0
29 * Turning on heavy statistics will turn off the managed allocator and
30 * the managed write barrier.
32 // #define HEAVY_STATISTICS
34 #ifdef HEAVY_STATISTICS
35 #define HEAVY_STAT(x) x
41 * Define this to allow the user to change the nursery size by
42 * specifying its value in the MONO_GC_PARAMS environmental
43 * variable. See mono_gc_base_init for details.
48 * The binary protocol enables logging a lot of the GC ativity in a way that is not very
49 * intrusive and produces a compact file that can be searched using a custom tool. This
50 * option enables very fine-grained binary protocol events, which will make the GC a tiny
51 * bit less efficient even if no binary protocol file is generated.
53 //#define SGEN_HEAVY_BINARY_PROTOCOL
56 * This extends the heavy binary protocol to record the provenance of an object
57 * for every allocation.
59 //#define SGEN_OBJECT_PROVENANCE
62 * This enables checks whenever objects are enqueued in gray queues.
63 * Right now the only check done is that we never enqueue nursery
64 * pointers in the concurrent collector.
66 //#define SGEN_CHECK_GRAY_OBJECT_ENQUEUE
69 * This keeps track of where a gray object queue section is and
70 * whether it is where it should be.
72 //#define SGEN_CHECK_GRAY_OBJECT_SECTIONS
75 * Enable this to check every reference update for null references and whether the update is
76 * made in a worker thread. In only a few cases do we potentially update references by
77 * writing nulls, so we assert in all the cases where it's not allowed. The concurrent
78 * collector's worker thread is not allowed to update references at all, so we also assert
79 * that we're not in the worker thread.
81 //#define SGEN_CHECK_UPDATE_REFERENCE
84 * Define this and use the "xdomain-checks" MONO_GC_DEBUG option to
85 * have cross-domain checks in the write barrier.
87 //#define XDOMAIN_CHECKS_IN_WBARRIER
90 * Define this to get number of objects marked information in the
91 * concurrent GC DTrace probes. Has a small performance impact, so
92 * it's disabled by default.
94 //#define SGEN_COUNT_NUMBER_OF_MAJOR_OBJECTS_MARKED
97 * Object layout statistics gather a histogram of reference locations
98 * over all scanned objects. We use this information to improve GC
99 * descriptors to speed up scanning. This does not provide any
100 * troubleshooting assistance (unless you are troubled in highly
101 * unusual ways) and makes scanning slower.
103 //#define SGEN_OBJECT_LAYOUT_STATISTICS
105 #ifndef SGEN_HEAVY_BINARY_PROTOCOL
106 #ifndef HEAVY_STATISTICS
107 #define MANAGED_ALLOCATION
108 #ifndef XDOMAIN_CHECKS_IN_WBARRIER
109 #define MANAGED_WBARRIER
115 * Maximum level of debug to enable on this build.
116 * Making this a constant enables us to put logging in a lot of places and
117 * not pay its cost on release builds.
119 #define SGEN_MAX_DEBUG_LEVEL 2
122 * Maximum level of asserts to enable on this build.
123 * FIXME replace all magic numbers with defines.
125 #define SGEN_MAX_ASSERT_LEVEL 5
128 #define GC_BITS_PER_WORD (sizeof (mword) * 8)
130 /*Size of the section used by the copying GC. */
131 #define SGEN_SIZEOF_GC_MEM_SECTION ((sizeof (GCMemSection) + 7) & ~7)
134 * to quickly find the head of an object pinned by a conservative
135 * address we keep track of the objects allocated for each
136 * SGEN_SCAN_START_SIZE memory chunk in the nursery or other memory
137 * sections. Larger values have less memory overhead and bigger
138 * runtime cost. 4-8 KB are reasonable values.
140 #define SGEN_SCAN_START_SIZE (4096*2)
143 * Objects bigger then this go into the large object space. This size has a few
144 * constraints. At least two of them must fit into a major heap block. It must also play
145 * well with the run length GC descriptor, which encodes the object size.
147 #define SGEN_MAX_SMALL_OBJ_SIZE 8000
150 * This is the maximum ammount of memory we're willing to waste in order to speed up allocation.
151 * Wastage comes in thre forms:
153 * -when building the nursery fragment list, small regions are discarded;
154 * -when allocating memory from a fragment if it ends up below the threshold, we remove it from the fragment list; and
155 * -when allocating a new tlab, we discard the remaining space of the old one
157 * Increasing this value speeds up allocation but will cause more frequent nursery collections as less space will be used.
158 * Descreasing this value will cause allocation to be slower since we'll have to cycle thru more fragments.
159 * 512 annedoctally keeps wastage under control and doesn't impact allocation performance too much.
161 #define SGEN_MAX_NURSERY_WASTE 512
165 * Minimum allowance for nursery allocations, as a multiple of the size of nursery.
167 * We allow at least this much allocation to happen to the major heap from multiple
168 * minor collections before triggering a major collection.
170 * Bigger values increases throughput by allowing more garbage to sit in the major heap.
171 * Smaller values leads to better memory effiency but more frequent major collections.
173 #define SGEN_DEFAULT_ALLOWANCE_NURSERY_SIZE_RATIO 4.0
175 #define SGEN_MIN_ALLOWANCE_NURSERY_SIZE_RATIO 1.0
176 #define SGEN_MAX_ALLOWANCE_NURSERY_SIZE_RATIO 10.0
179 * How much more we allow the heap to grow before triggering another major collection
181 #define SGEN_DEFAULT_ALLOWANCE_HEAP_SIZE_RATIO 0.33
184 * Default ratio of memory we want to release in a major collection in relation to the the current heap size.
186 * A major collection target is to free a given amount of memory. This amount is a ratio of the major heap size.
188 * Values above 0.5 cause the heap to agressively grow when it's small and waste memory when it's big.
189 * Lower values will produce more reasonable sized heaps when it's small, but will be suboptimal at large
190 * sizes as they will use a small fraction only.
193 #define SGEN_DEFAULT_SAVE_TARGET_RATIO 0.5
195 #define SGEN_MIN_SAVE_TARGET_RATIO 0.1
196 #define SGEN_MAX_SAVE_TARGET_RATIO 2.0
199 * Configurable cementing parameters.
201 * If there are too many pinned nursery objects with many references
202 * from the major heap, the hash table size must be increased.
204 * The threshold is the number of references from the major heap to a
205 * pinned nursery object which triggers cementing: if there are more
206 * than that number of references, the pinned object is cemented until
207 * the next major collection.
209 #define SGEN_CEMENT_HASH_SHIFT 6
210 #define SGEN_CEMENT_HASH_SIZE (1 << SGEN_CEMENT_HASH_SHIFT)
211 #define SGEN_CEMENT_HASH(hv) (((hv) ^ ((hv) >> SGEN_CEMENT_HASH_SHIFT)) & (SGEN_CEMENT_HASH_SIZE - 1))
212 #define SGEN_CEMENT_THRESHOLD 1000