Commit 066d28b9 authored by Ian Lynagh's avatar Ian Lynagh

On Windows, when returning memory to the OS, we try to release it

as well as decommiting it.
parent c53c1c16
......@@ -211,6 +211,10 @@ void osFreeMBlocks(char *addr, nat n)
munmap(addr, n * MBLOCK_SIZE);
}
void osReleaseFreeMemory(void) {
/* Nothing to do on POSIX */
}
void osFreeAllMBlocks(void)
{
void *mblock;
......
......@@ -697,6 +697,8 @@ void returnMemoryToOS(nat n /* megablocks */)
}
free_mblock_list = bd;
osReleaseFreeMemory();
IF_DEBUG(gc,
if (n != 0) {
debugBelch("Wanted to free %d more MBlocks than are freeable\n",
......
......@@ -14,6 +14,7 @@
void osMemInit(void);
void *osGetMBlocks(nat n);
void osFreeMBlocks(char *addr, nat n);
void osReleaseFreeMemory(void);
void osFreeAllMBlocks(void);
lnat getPageSize (void);
void setExecutable (void *p, lnat len, rtsBool exec);
......
......@@ -14,9 +14,6 @@
#include <windows.h>
#endif
/* alloc_rec keeps the info we need to have matching VirtualAlloc and
VirtualFree calls.
*/
typedef struct alloc_rec_ {
char* base; /* non-aligned base address, directly from VirtualAlloc */
int size; /* Size in bytes */
......@@ -29,7 +26,12 @@ typedef struct block_rec_ {
struct block_rec_* next;
} block_rec;
/* allocs are kept in ascending order, and are the memory regions as
returned by the OS as we need to have matching VirtualAlloc and
VirtualFree calls. */
static alloc_rec* allocs = NULL;
/* free_blocks are kept in ascending order, and adjacent blocks are merged */
static block_rec* free_blocks = NULL;
void
......@@ -239,6 +241,88 @@ void osFreeMBlocks(char *addr, nat n)
}
}
void osReleaseFreeMemory(void)
{
alloc_rec *prev_a, *a;
alloc_rec head_a;
block_rec *prev_fb, *fb;
block_rec head_fb;
char *a_end, *fb_end;
/* go through allocs and free_blocks in lockstep, looking for allocs
that are completely free, and uncommit them */
head_a.base = 0;
head_a.size = 0;
head_a.next = allocs;
head_fb.base = 0;
head_fb.size = 0;
head_fb.next = free_blocks;
prev_a = &head_a;
a = allocs;
prev_fb = &head_fb;
fb = free_blocks;
while (a != NULL) {
a_end = a->base + a->size;
while (fb != NULL && fb->base + fb->size < a_end) {
prev_fb = fb;
fb = fb->next;
}
fb_end = fb->base + fb->size;
if (fb->base <= a->base) {
/* The alloc is within the free block. Now we need to know
if it sticks out at either end. */
if (fb_end == a_end) {
if (fb->base == a->base) {
/* fb and a are identical, so just free fb */
prev_fb->next = fb->next;
stgFree(fb);
fb = prev_fb->next;
}
else {
/* fb begins earlier, so truncate it to not include a */
fb->size = a->base - fb->base;
}
}
else {
/* fb ends later, so we'll make fb just be the part
after a. First though, if it also starts earlier,
we make a new free block record for the before bit. */
if (fb->base != a->base) {
block_rec *new_fb;
new_fb = (block_rec *)stgMallocBytes(sizeof(block_rec),"osReleaseFreeMemory");
new_fb->base = fb->base;
new_fb->size = a->base - fb->base;
new_fb->next = fb;
prev_fb->next = new_fb;
}
fb->size = fb_end - a_end;
fb->base = a_end;
}
/* Now we can free the alloc */
prev_a->next = a->next;
if(!VirtualFree((void *)a->base, 0, MEM_RELEASE)) {
sysErrorBelch("freeAllMBlocks: VirtualFree MEM_RELEASE failed");
stg_exit(EXIT_FAILURE);
}
stgFree(a);
a = prev_a->next;
}
else {
/* Otherwise this alloc is not freeable, so go on to the
next one */
prev_a = a;
a = a->next;
}
}
allocs = head_a.next;
free_blocks = head_fb.next;
}
void
osFreeAllMBlocks(void)
{
......
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