summaryrefslogtreecommitdiff
path: root/src/base/fast_alloc.hh
diff options
context:
space:
mode:
Diffstat (limited to 'src/base/fast_alloc.hh')
-rw-r--r--src/base/fast_alloc.hh214
1 files changed, 214 insertions, 0 deletions
diff --git a/src/base/fast_alloc.hh b/src/base/fast_alloc.hh
new file mode 100644
index 000000000..54e35f8e0
--- /dev/null
+++ b/src/base/fast_alloc.hh
@@ -0,0 +1,214 @@
+/*
+ * Copyright (c) 2000-2001, 2003-2005 The Regents of The University of Michigan
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met: redistributions of source code must retain the above copyright
+ * notice, this list of conditions and the following disclaimer;
+ * redistributions in binary form must reproduce the above copyright
+ * notice, this list of conditions and the following disclaimer in the
+ * documentation and/or other materials provided with the distribution;
+ * neither the name of the copyright holders nor the names of its
+ * contributors may be used to endorse or promote products derived from
+ * this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+/*
+ * This code was originally written by Steve Reinhardt as part of
+ * the Wisconsin Wind Tunnel simulator. Relicensed as part of M5
+ * by permission.
+ */
+
+#ifndef __FAST_ALLOC_H__
+#define __FAST_ALLOC_H__
+
+#include <stddef.h>
+
+// Fast structure allocator. Designed for small objects that are
+// frequently allocated and deallocated. This code is derived from the
+// 'alloc_struct' package used in WWT and Blizzard. C++ provides a
+// much nicer framework for the same optimization. The package is
+// implemented as a class, FastAlloc. Allocation and deletion are
+// performed using FastAlloc's new and delete operators. Any object
+// that derives from the FastAlloc class will transparently use this
+// allocation package.
+
+// The static allocate() and deallocate() methods can also be called
+// directly if desired.
+
+// In order for derived classes to call delete with the correct
+// structure size even when they are deallocated via a base-type
+// pointer, they must have a virtual destructor. It is sufficient for
+// FastAlloc to declare a virtual destructor (as it does); it is not
+// required for derived classes to declare their own destructor. The
+// compiler will automatically generate a virtual destructor for each
+// derived class. However, it is more efficient if each derived class
+// defines an inline destructor, so that the compiler can statically
+// collapse the destructor call chain back up the inheritance
+// hierarchy.
+
+// Uncomment this #define to track in-use objects
+// (for debugging memory leaks).
+//#define FAST_ALLOC_DEBUG
+
+// Uncomment this #define to count news, deletes, and chunk allocations
+// (by bucket).
+// #define FAST_ALLOC_STATS
+
+#include "config/no_fast_alloc.hh"
+
+#if NO_FAST_ALLOC
+
+class FastAlloc {
+};
+
+#else
+
+class FastAlloc {
+ public:
+
+ static void *allocate(size_t);
+ static void deallocate(void *, size_t);
+
+ void *operator new(size_t);
+ void operator delete(void *, size_t);
+
+#ifdef FAST_ALLOC_DEBUG
+ FastAlloc();
+ FastAlloc(FastAlloc*,FastAlloc*); // for inUseHead, see below
+ virtual ~FastAlloc();
+#else
+ virtual ~FastAlloc() {}
+#endif
+
+ private:
+
+ // Max_Alloc_Size is the largest object that can be allocated with
+ // this class. There's no fundamental limit, but this limits the
+ // size of the freeLists array. Let's not make this really huge
+ // like in Blizzard.
+ static const int Max_Alloc_Size = 512;
+
+ // Alloc_Quantum is the difference in size between adjacent
+ // buckets in the free list array.
+ static const int Log2_Alloc_Quantum = 3;
+ static const int Alloc_Quantum = (1 << Log2_Alloc_Quantum);
+
+ // Num_Buckets = bucketFor(Max_Alloc_Size) + 1
+ static const int Num_Buckets =
+ ((Max_Alloc_Size + Alloc_Quantum - 1) >> Log2_Alloc_Quantum) + 1;
+
+ // when we call new() for more structures, how many should we get?
+ static const int Num_Structs_Per_New = 20;
+
+ static int bucketFor(size_t);
+ static void *moreStructs(int bucket);
+
+ static void *freeLists[Num_Buckets];
+
+#ifdef FAST_ALLOC_STATS
+ static unsigned newCount[Num_Buckets];
+ static unsigned deleteCount[Num_Buckets];
+ static unsigned allocCount[Num_Buckets];
+#endif
+
+#ifdef FAST_ALLOC_DEBUG
+ // per-object debugging fields
+ bool inUse; // in-use flag
+ FastAlloc *inUsePrev; // ptrs to build list of in-use objects
+ FastAlloc *inUseNext;
+
+ // static (global) debugging vars
+ static int numInUse; // count in-use objects
+ static FastAlloc inUseHead; // dummy head for list of in-use objects
+
+ public:
+ // functions to dump debugging info (see fast_alloc.cc for C
+ // versions that might be more agreeable to call from gdb)
+ static void dump_summary();
+ static void dump_oldest(int n);
+#endif
+};
+
+
+inline
+int FastAlloc::bucketFor(size_t sz)
+{
+ return (sz + Alloc_Quantum - 1) >> Log2_Alloc_Quantum;
+}
+
+
+inline
+void *FastAlloc::allocate(size_t sz)
+{
+ int b;
+ void *p;
+
+ if (sz > Max_Alloc_Size)
+ return (void *)::new char[sz];
+
+ b = bucketFor(sz);
+ p = freeLists[b];
+
+ if (p)
+ freeLists[b] = *(void **)p;
+ else
+ p = moreStructs(b);
+
+#ifdef FAST_ALLOC_STATS
+ ++newCount[b];
+#endif
+
+ return p;
+}
+
+
+inline
+void FastAlloc::deallocate(void *p, size_t sz)
+{
+ int b;
+
+ if (sz > Max_Alloc_Size)
+ {
+ ::delete [] (char *)p;
+ return;
+ }
+
+ b = bucketFor(sz);
+ *(void **)p = freeLists[b];
+ freeLists[b] = p;
+#ifdef FAST_ALLOC_STATS
+ ++deleteCount[b];
+#endif
+}
+
+
+inline
+void *FastAlloc::operator new(size_t sz)
+{
+ return allocate(sz);
+}
+
+
+inline
+void FastAlloc::operator delete(void *p, size_t sz)
+{
+ deallocate(p, sz);
+}
+
+#endif // NO_FAST_ALLOC
+
+#endif // __FAST_ALLOC_H__