/* -----------------------------------------------------------------------------
- * $Id: MBlock.c,v 1.29 2002/07/17 09:21:50 simonmar Exp $
+ * $Id: MBlock.c,v 1.30 2002/10/21 11:38:53 simonmar Exp $
*
* (c) The GHC Team 1998-1999
*
#include "MBlock.h"
#include "BlockAlloc.h"
+#ifdef HAVE_STDLIB_H
+#include <stdlib.h>
+#endif
#ifdef HAVE_UNISTD_H
#include <unistd.h>
#endif
-
#ifdef HAVE_SYS_TYPES_H
#include <sys/types.h>
#endif
-
#ifndef mingw32_TARGET_OS
# ifdef HAVE_SYS_MMAN_H
# include <sys/mman.h>
# endif
#endif
-
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif
-
#if HAVE_WINDOWS_H
#include <windows.h>
#endif
lnat mblocks_allocated = 0;
+/* -----------------------------------------------------------------------------
+ The MBlock Map: provides our implementation of HEAP_ALLOCED()
+ -------------------------------------------------------------------------- */
+
+StgWord8 mblock_map[4096]; // initially all zeros
+
+static void
+mblockIsHeap (void *p)
+{
+ mblock_map[((StgWord)p & ~MBLOCK_MASK) >> MBLOCK_SHIFT] = 1;
+}
+
+/* -----------------------------------------------------------------------------
+ Allocate new mblock(s)
+ -------------------------------------------------------------------------- */
+
void *
getMBlock(void)
{
return getMBlocks(1);
}
+/* -----------------------------------------------------------------------------
+ The mmap() method
+
+ On Unix-like systems, we use mmap() to allocate our memory. We
+ want memory in chunks of MBLOCK_SIZE, and aligned on an MBLOCK_SIZE
+ boundary. The mmap() interface doesn't give us this level of
+ control, so we have to use some heuristics.
+
+ In the general case, if we want a block of n megablocks, then we
+ allocate n+1 and trim off the slop from either side (using
+ munmap()) to get an aligned chunk of size n. However, the next
+ time we'll try to allocate directly after the previously allocated
+ chunk, on the grounds that this is aligned and likely to be free.
+ If it turns out that we were wrong, we have to munmap() and try
+ again using the general method.
+ -------------------------------------------------------------------------- */
+
#if !defined(mingw32_TARGET_OS) && !defined(cygwin32_TARGET_OS)
+
+// A wrapper around mmap(), to abstract away from OS differences in
+// the mmap() interface.
+
+static void *
+my_mmap (void *addr, int size)
+{
+ void *ret;
+
+#ifdef solaris2_TARGET_OS
+ {
+ int fd = open("/dev/zero",O_RDONLY);
+ ret = mmap(addr, size, PROT_READ | PROT_WRITE,
+ MAP_FIXED | MAP_PRIVATE, fd, 0);
+ close(fd);
+ }
+#elif hpux_TARGET_OS
+ ret = mmap(addr, size, PROT_READ | PROT_WRITE,
+ MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
+#elif darwin_TARGET_OS
+ ret = mmap(addr, size, PROT_READ | PROT_WRITE,
+ MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0);
+#else
+ ret = mmap(addr, size, PROT_READ | PROT_WRITE,
+ MAP_ANON | MAP_PRIVATE, -1, 0);
+#endif
+
+ return ret;
+}
+
+// Implements the general case: allocate a chunk of memory of 'size'
+// mblocks.
+
+static void *
+gen_map_mblocks (int size)
+{
+ int slop;
+ void *ret;
+
+ // Try to map a larger block, and take the aligned portion from
+ // it (unmap the rest).
+ size += MBLOCK_SIZE;
+ ret = my_mmap(0, size);
+ if (ret == (void *)-1) {
+ barf("gen_map_mblocks: mmap failed");
+ }
+
+ // unmap the slop bits around the chunk we allocated
+ slop = (W_)ret & MBLOCK_MASK;
+
+ if (munmap(ret, MBLOCK_SIZE - slop) == -1) {
+ barf("gen_map_mblocks: munmap failed");
+ }
+ if (slop > 0 && munmap(ret+size-slop, slop) == -1) {
+ barf("gen_map_mblocks: munmap failed");
+ }
+
+ // next time, try after the block we just got.
+ ret += MBLOCK_SIZE - slop;
+ return ret;
+}
+
+
+// The external interface: allocate 'n' mblocks, and return the
+// address.
+
void *
getMBlocks(nat n)
{
static caddr_t next_request = (caddr_t)HEAP_BASE;
caddr_t ret;
lnat size = MBLOCK_SIZE * n;
+ nat i;
-#ifdef solaris2_TARGET_OS
- {
- int fd = open("/dev/zero",O_RDONLY);
- ret = mmap(next_request, size, PROT_READ | PROT_WRITE,
- MAP_FIXED | MAP_PRIVATE, fd, 0);
- close(fd);
- }
-#elif hpux_TARGET_OS
- ret = mmap(next_request, size, PROT_READ | PROT_WRITE,
- MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
-#elif darwin_TARGET_OS
- ret = mmap(next_request, size, PROT_READ | PROT_WRITE,
- MAP_FIXED | MAP_ANON | MAP_PRIVATE, -1, 0);
-#else
- ret = mmap(next_request, size, PROT_READ | PROT_WRITE,
- MAP_ANON | MAP_PRIVATE, -1, 0);
-#endif
+ if (next_request == 0) {
+ // use gen_map_mblocks the first time.
+ ret = gen_map_mblocks(size);
+ } else {
+ ret = my_mmap(next_request, size);
- if (ret == (void *)-1) {
- if (errno == ENOMEM) {
- barf("getMBlock: out of memory (blocks requested: %d)", n);
- } else {
- barf("GetMBlock: mmap failed");
- }
- }
+ if (ret == (void *)-1) {
+ if (errno == ENOMEM) {
+ belch("out of memory (requested %d bytes)", n * BLOCK_SIZE);
+ stg_exit(EXIT_FAILURE);
+ } else {
+ barf("getMBlock: mmap failed");
+ }
+ }
- if (((W_)ret & MBLOCK_MASK) != 0) {
- barf("GetMBlock: misaligned block %p returned when allocating %d megablock(s) at %p", ret, n, next_request);
+ if (((W_)ret & MBLOCK_MASK) != 0) {
+ // misaligned block!
+#ifdef DEBUG
+ belch("getMBlock: misaligned block %p returned when allocating %d megablock(s) at %p", ret, n, next_request);
+#endif
+
+ // unmap this block...
+ if (munmap(ret, size) == -1) {
+ barf("getMBlock: munmap failed");
+ }
+ // and do it the hard way
+ ret = gen_map_mblocks(size);
+ }
}
+ // Next time, we'll try to allocate right after the block we just got.
+ next_request = ret + size;
+
IF_DEBUG(gc,fprintf(stderr,"Allocated %d megablock(s) at %p\n",n,ret));
- next_request += size;
+ // fill in the table
+ for (i = 0; i < n; i++) {
+ mblockIsHeap( ret + i * MBLOCK_SIZE );
+ }
mblocks_allocated += n;
-
+
return ret;
}
/* Number of bytes reserved */
static unsigned long size_reserved_pool = SIZE_RESERVED_POOL;
-/* This predicate should be inlined, really. */
-/* TODO: this only works for a single chunk */
-int
-is_heap_alloced(const void* x)
-{
- return (((char*)(x) >= base_non_committed) &&
- ((char*)(x) <= end_non_committed));
-}
-
void *
getMBlocks(nat n)
{
mblocks_allocated += n;
+ // fill in the table
+ for (i = 0; i < n; i++) {
+ mblockIsHeap( ret + i * MBLOCK_SIZE );
+ }
+
return ret;
}
/* -----------------------------------------------------------------------------
- * $Id: MBlock.h,v 1.14 2002/05/14 08:15:49 matthewc Exp $
+ * $Id: MBlock.h,v 1.15 2002/10/21 11:38:54 simonmar Exp $
*
* (c) The GHC Team, 1998-1999
*
* MegaBlock Allocator interface.
*
* ---------------------------------------------------------------------------*/
+
#ifndef __MBLOCK_H__
#define __MBLOCK_H__
extern lnat mblocks_allocated;
-#if defined(mingw32_TARGET_OS)
-extern int is_heap_alloced(const void* p);
-#endif
-
extern void * getMBlock(void);
extern void * getMBlocks(nat n);
-#if freebsd2_TARGET_OS || freebsd_TARGET_OS
-/* Executable is loaded from 0x0
- * Shared libraries are loaded at 0x2000000
- * Stack is at the top of the address space. The kernel probably owns
- * 0x8000000 onwards, so we'll pick 0x5000000.
- */
-#define HEAP_BASE 0x50000000
-
-#elif netbsd_TARGET_OS
-/* NetBSD i386 shared libs are at 0x40000000
- */
-#define HEAP_BASE 0x50000000
-#elif openbsd_TARGET_OS
-#define HEAP_BASE 0x50000000
-
-#elif linux_TARGET_OS
-#if ia64_TARGET_ARCH
-/* Shared libraries are in region 1, text in region 2, data in region 3.
- * Stack is at the top of region 4. We use the bottom.
- */
-#define HEAP_BASE (4L<<61)
-#else
-/* Any ideas?
- */
-#define HEAP_BASE 0x50000000
-#endif
-
-#elif solaris2_TARGET_OS
-/* guess */
-#define HEAP_BASE 0x50000000
-
-#elif osf3_TARGET_OS
+#if osf3_TARGET_OS
/* ToDo: Perhaps by adjusting this value we can make linking without
* -static work (i.e., not generate a core-dumping executable)? */
#if SIZEOF_VOID_P == 8
#error I have no idea where to begin the heap on a non-64-bit osf3 machine.
#endif
-#elif hpux_TARGET_OS
-/* guess */
-#define HEAP_BASE 0x50000000
+#else
-#elif darwin_TARGET_OS
-/* guess */
-#define HEAP_BASE 0x50000000
+// we're using the generic method
+#define HEAP_BASE 0
-#elif defined(mingw32_TARGET_OS) || defined(cygwin32_TARGET_OS)
-/* doesn't matter, we use a reserve/commit algorithm */
+#endif
+
+/* -----------------------------------------------------------------------------
+ The HEAP_ALLOCED() test.
+ HEAP_ALLOCED is called FOR EVERY SINGLE CLOSURE during GC.
+ It needs to be FAST.
+
+ Implementation of HEAP_ALLOCED
+ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+ Since heap is allocated in chunks of megablocks (MBLOCK_SIZE), we
+ can just use a table to record which megablocks in the address
+ space belong to the heap. On a 32-bit machine, with 1Mb
+ megablocks, using 8 bits for each entry in the table, the table
+ requires 4k. Lookups during GC will be fast, because the table
+ will be quickly cached (indeed, performance measurements showed no
+ measurable difference between doing the table lookup and using a
+ constant comparison).
+ -------------------------------------------------------------------------- */
+
+#if SIZEOF_VOID_P == 4
+
+// This is the table. Each byte is non-zero if the appropriate MBlock
+// in the address space contains heap.
+extern StgWord8 mblock_map[];
+
+#define HEAP_ALLOCED(p) \
+ ((int)(mblock_map[((StgWord)(p) & ~MBLOCK_MASK) >> MBLOCK_SHIFT]))
+
+#else // SIZEOF_VOID_P != 4
+
+// on a 64-bit machine, we need to extend the above scheme to use a
+// 2-level mapping. (ToDo)
+
+#ifdef TEXT_BEFORE_HEAP
+# define HEAP_ALLOCED(x) ((StgPtr)(x) >= (StgPtr)(HEAP_BASE))
#else
-#error Dont know where to get memory from on this architecture
-/* ToDo: memory locations on other architectures */
+#error HEAP_ALLOCED not defined
#endif
-#endif
+#endif // SIZEOF_VOID_P != 4
+
+#endif // __MBLOCK_H__
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