path: root/js/src/gc/Memory.cpp

/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 4 -*-
 * vim: set ts=8 sts=4 et sw=4 tw=99:
 * This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

#include "gc/Memory.h"

#include "jscntxt.h"

#include "js/HeapAPI.h"

using namespace js;
using namespace js::gc;

static bool
DecommitEnabled(JSRuntime *rt)
{
    return rt->gcSystemPageSize == ArenaSize;
}

#if defined(XP_WIN)
#include "jswin.h"
#include <psapi.h>

void
gc::InitMemorySubsystem(JSRuntime *rt)
{
    SYSTEM_INFO sysinfo;
    GetSystemInfo(&sysinfo);
    rt->gcSystemPageSize = sysinfo.dwPageSize;
    rt->gcSystemAllocGranularity = sysinfo.dwAllocationGranularity;
}

void *
gc::MapAlignedPages(JSRuntime *rt, size_t size, size_t alignment)
{
    JS_ASSERT(size >= alignment);
    JS_ASSERT(size % alignment == 0);
    JS_ASSERT(size % rt->gcSystemPageSize == 0);
    JS_ASSERT(alignment % rt->gcSystemAllocGranularity == 0);

    /* Special case: If we want allocation alignment, no further work is needed. */
    if (alignment == rt->gcSystemAllocGranularity) {
        return VirtualAlloc(NULL, size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);
    }

    /*
     * Windows requires that there be a 1:1 mapping between VM allocation
     * and deallocation operations.  Therefore, take care here to acquire the
     * final result via one mapping operation.  This means unmapping any
     * preliminary result that is not correctly aligned.
     */
    void *p = NULL;
    while (!p) {
        /*
         * Over-allocate in order to map a memory region that is
         * definitely large enough then deallocate and allocate again the
         * correct sizee, within the over-sized mapping.
         *
         * Since we're going to unmap the whole thing anyway, the first
         * mapping doesn't have to commit pages.
         */
        p = VirtualAlloc(NULL, size * 2, MEM_RESERVE, PAGE_READWRITE);
        if (!p)
            return NULL;
        void *chunkStart = (void *)(uintptr_t(p) + (alignment - (uintptr_t(p) % alignment)));
        UnmapPages(rt, p, size * 2);
        p = VirtualAlloc(chunkStart, size, MEM_COMMIT | MEM_RESERVE, PAGE_READWRITE);

        /* Failure here indicates a race with another thread, so try again. */
    }

    JS_ASSERT(uintptr_t(p) % alignment == 0);
    return p;
}

void
gc::UnmapPages(JSRuntime *rt, void *p, size_t size)
{
    JS_ALWAYS_TRUE(VirtualFree(p, 0, MEM_RELEASE));
}

bool
gc::MarkPagesUnused(JSRuntime *rt, void *p, size_t size)
{
    if (!DecommitEnabled(rt))
        return true;

    JS_ASSERT(uintptr_t(p) % rt->gcSystemPageSize == 0);
    LPVOID p2 = VirtualAlloc(p, size, MEM_RESET, PAGE_READWRITE);
    return p2 == p;
}

bool
gc::MarkPagesInUse(JSRuntime *rt, void *p, size_t size)
{
    JS_ASSERT(uintptr_t(p) % rt->gcSystemPageSize == 0);
    return true;
}

size_t
gc::GetPageFaultCount()
{
    PROCESS_MEMORY_COUNTERS pmc;
    if (!GetProcessMemoryInfo(GetCurrentProcess(), &pmc, sizeof(pmc)))
        return 0;
    return pmc.PageFaultCount;
}

#elif defined(SOLARIS)

#include <sys/mman.h>
#include <unistd.h>

#ifndef MAP_NOSYNC
# define MAP_NOSYNC 0
#endif

void
gc::InitMemorySubsystem(JSRuntime *rt)
{
    rt->gcSystemPageSize = rt->gcSystemAllocGranularity = size_t(sysconf(_SC_PAGESIZE));
}

void *
gc::MapAlignedPages(JSRuntime *rt, size_t size, size_t alignment)
{
    JS_ASSERT(size >= alignment);
    JS_ASSERT(size % alignment == 0);
    JS_ASSERT(size % rt->gcSystemPageSize == 0);
    JS_ASSERT(alignment % rt->gcSystemAllocGranularity == 0);

    int prot = PROT_READ | PROT_WRITE;
    int flags = MAP_PRIVATE | MAP_ANON | MAP_ALIGN | MAP_NOSYNC;

    void *p = mmap((caddr_t)alignment, size, prot, flags, -1, 0);
    if (p == MAP_FAILED)
        return NULL;
    return p;
}

void
gc::UnmapPages(JSRuntime *rt, void *p, size_t size)
{
    JS_ALWAYS_TRUE(0 == munmap((caddr_t)p, size));
}

bool
gc::MarkPagesUnused(JSRuntime *rt, void *p, size_t size)
{
    JS_ASSERT(uintptr_t(p) % rt->gcSystemPageSize == 0);
    return true;
}

bool
gc::MarkPagesInUse(JSRuntime *rt, void *p, size_t size)
{
    JS_ASSERT(uintptr_t(p) % rt->gcSystemPageSize == 0);
    return true;
}

size_t
gc::GetPageFaultCount()
{
    return 0;
}

#elif defined(XP_UNIX) || defined(XP_MACOSX) || defined(DARWIN)

#include <sys/mman.h>
#include <sys/resource.h>
#include <unistd.h>

void
gc::InitMemorySubsystem(JSRuntime *rt)
{
    rt->gcSystemPageSize = rt->gcSystemAllocGranularity = size_t(sysconf(_SC_PAGESIZE));
}

static inline void *
MapMemory(size_t length, int prot, int flags, int fd, off_t offset)
{
#if defined(__ia64__)
    /*
     * The JS engine assumes that all allocated pointers have their high 17 bits clear,
     * which ia64's mmap doesn't support directly. However, we can emulate it by passing
     * mmap an "addr" parameter with those bits clear. The mmap will return that address,
     * or the nearest available memory above that address, providing a near-guarantee
     * that those bits are clear. If they are not, we return NULL below to indicate
     * out-of-memory.
     *
     * The addr is chosen as 0x0000070000000000, which still allows about 120TB of virtual
     * address space.
     *
     * See Bug 589735 for more information.
     */
    void *region = mmap((void*)0x0000070000000000, length, prot, flags, fd, offset);
    if (region == MAP_FAILED)
        return MAP_FAILED;
    /* 
     * If the allocated memory doesn't have its upper 17 bits clear, consider it
     * as out of memory.
     */
    if ((uintptr_t(region) + (length - 1)) & 0xffff800000000000) {
        JS_ALWAYS_TRUE(0 == munmap(region, length));
        return MAP_FAILED;
    }
    return region;
#else
    return mmap(NULL, length, prot, flags, fd, offset);
#endif
}

void *
gc::MapAlignedPages(JSRuntime *rt, size_t size, size_t alignment)
{
    JS_ASSERT(size >= alignment);
    JS_ASSERT(size % alignment == 0);
    JS_ASSERT(size % rt->gcSystemPageSize == 0);
    JS_ASSERT(alignment % rt->gcSystemAllocGranularity == 0);

    int prot = PROT_READ | PROT_WRITE;
    int flags = MAP_PRIVATE | MAP_ANON;

    /* Special case: If we want page alignment, no further work is needed. */
    if (alignment == rt->gcSystemAllocGranularity) {
        void *region = MapMemory(size, prot, flags, -1, 0);
        if (region == MAP_FAILED)
            return NULL;
        return region;
    }

    /* Overallocate and unmap the region's edges. */
    size_t reqSize = Min(size + 2 * alignment, 2 * size);
    void *region = MapMemory(reqSize, prot, flags, -1, 0);
    if (region == MAP_FAILED)
        return NULL;

    uintptr_t regionEnd = uintptr_t(region) + reqSize;
    uintptr_t offset = uintptr_t(region) % alignment;
    JS_ASSERT(offset < reqSize - size);

    void *front = (void *)(uintptr_t(region) + (alignment - offset));
    void *end = (void *)(uintptr_t(front) + size);
    if (front != region)
        JS_ALWAYS_TRUE(0 == munmap(region, alignment - offset));
    if (uintptr_t(end) != regionEnd)
        JS_ALWAYS_TRUE(0 == munmap(end, regionEnd - uintptr_t(end)));

    JS_ASSERT(uintptr_t(front) % alignment == 0);
    return front;
}

void
gc::UnmapPages(JSRuntime *rt, void *p, size_t size)
{
    JS_ALWAYS_TRUE(0 == munmap(p, size));
}

bool
gc::MarkPagesUnused(JSRuntime *rt, void *p, size_t size)
{
    if (!DecommitEnabled(rt))
        return false;

    JS_ASSERT(uintptr_t(p) % rt->gcSystemPageSize == 0);
    int result = madvise(p, size, MADV_DONTNEED);
    return result != -1;
}

bool
gc::MarkPagesInUse(JSRuntime *rt, void *p, size_t size)
{
    JS_ASSERT(uintptr_t(p) % rt->gcSystemPageSize == 0);
    return true;
}

size_t
gc::GetPageFaultCount()
{
    struct rusage usage;
    int err = getrusage(RUSAGE_SELF, &usage);
    if (err)
        return 0;
    return usage.ru_majflt;
}

#else
#error "Memory mapping functions are not defined for your OS."
#endif