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Proper memory commitment

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This commit is contained in:
Nils O. Selåsdal
2026-06-09 01:06:48 +02:00
parent 6b9b058859
commit 1477f5b396
6 changed files with 123 additions and 78 deletions
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src/platform.c
+31 -36
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@@ -1,30 +1,18 @@
#include "base_core.h"
#include "platform.h"
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/mman.h>
#define IsPageAligned(x) (IsAlignedTo(x, platform_page_size()))
U32 platform_page_size(void)
{
return getpagesize();
}
static INLINE size_t AlignToPageSize(size_t size)
{
U32 page_size = platform_page_size();
size_t aligned_size = AlignUpPow2(size, page_size);
return aligned_size;
}
static INLINE size_t AlignToPageStart(size_t size)
{
U32 page_size = platform_page_size();
size_t aligned_size = AlignDownPow2(size, page_size);
return aligned_size;
}
void *platform_malloc(size_t size)
{
@@ -39,13 +27,10 @@ void platform_free(void *mem)
void *memory_allocate(size_t size)
{
if (size == 0) {
size = 1;
}
Assert(IsPow2(size));
size_t aligned_size = AlignToPageSize(size);
void *mem = mmap(0, aligned_size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
TRACEF("memory_allocate size=%zu aligned_size=%zu mem=%p\n", size, aligned_size, mem);
void *mem = mmap(0, size, PROT_READ | PROT_WRITE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
TRACEF("memory_allocate size=%zu mem=%p\n", size, mem);
if (mem == MAP_FAILED) {
mem = NULL;
}
@@ -54,36 +39,46 @@ void *memory_allocate(size_t size)
void memory_free(void *mem, size_t size)
{
size_t aligned_size = AlignToPageSize(size);
TRACEF(" memory_free size=%zu aligned_size=%zu mem=%p\n", size, aligned_size, mem);
int rc = munmap(mem, aligned_size);
TRACEF(" memory_free size=%zu mem=%p\n", size, mem);
Assert(IsPageAligned((uintptr_t)mem));
Assert(IsPageAligned(size));
int rc = munmap(mem, size);
Assert(rc == 0);
}
void *memory_reserve(size_t size)
{
Assert(IsPageAligned(size));
void *mem = mmap(0, size, PROT_NONE, MAP_ANONYMOUS | MAP_PRIVATE, -1, 0);
TRACEF("memory_reserve size=%zu mem=%p\n", size, mem);
if (mem == MAP_FAILED) {
mem = NULL;
}
return mem;
}
void memory_commit(void *mem, size_t size)
{
size_t aligned_size = AlignToPageSize(size);
void *aligned_mem = (void *)AlignToPageStart((uintptr_t)mem);
TRACEF("memory_commit size=%zu aligned_size=%zu ptr=%p aligned_mem=%p\n", size, aligned_size, mem, aligned_mem);
Assert(IsPageAligned((uintptr_t)mem));
Assert(IsPageAligned(size));
TRACEF("memory_commit size=%zu mem=%p\n", size, mem);
int rc;
rc = mprotect(aligned_mem, aligned_size, PROT_READ | PROT_WRITE);
rc = mprotect(mem, size, PROT_READ | PROT_WRITE);
Assert(rc == 0);
rc = madvise(aligned_mem, aligned_size, MADV_WILLNEED);
rc = madvise(mem, size, MADV_WILLNEED);
Assert(rc == 0);
}
void memory_decommit(void *mem, size_t size)
{
size_t aligned_size = AlignToPageSize(size);
void *aligned_mem = (void *)AlignToPageStart((uintptr_t)mem);
TRACEF("memory_commit size=%zu aligned_size=%zu ptr=%p aligned_mem=%p\n", size, aligned_size, mem, aligned_mem);
TRACEF("memory_decommit size=%zu mem=%p\n", size, mem);
Assert(IsPageAligned((uintptr_t)mem));
Assert(IsPageAligned(size));
int rc;
rc = mprotect(aligned_mem, aligned_size, PROT_NONE);
rc = mprotect(mem, size, PROT_NONE);
Assert(rc == 0);
rc = madvise(aligned_mem, aligned_size, MADV_DONTNEED);
rc = madvise(mem, size, MADV_DONTNEED);
Assert(rc == 0);
}