/*
* Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
* or visit www.oracle.com if you need additional information or have any
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*/
#include "precompiled.hpp"
#include "gc/z/zAddress.inline.hpp"
#include "gc/z/zErrno.hpp"
#include "gc/z/zGlobals.hpp"
#include "gc/z/zLargePages.inline.hpp"
#include "gc/z/zMemory.hpp"
#include "gc/z/zNUMA.hpp"
#include "gc/z/zPhysicalMemory.inline.hpp"
#include "gc/z/zPhysicalMemoryBacking_linux.hpp"
#include "logging/log.hpp"
#include "runtime/globals.hpp"
#include "runtime/init.hpp"
#include "runtime/os.hpp"
#include "utilities/align.hpp"
#include "utilities/debug.hpp"
#include <stdio.h>
#include <sys/mman.h>
#include <sys/types.h>
//
// Support for building on older Linux systems
//
// madvise(2) flags
#ifndef MADV_HUGEPAGE
#define MADV_HUGEPAGE 14
#endif
// Proc file entry for max map mount
#define ZFILENAME_PROC_MAX_MAP_COUNT "/proc/sys/vm/max_map_count"
bool ZPhysicalMemoryBacking::is_initialized() const {
return _file.is_initialized();
}
void ZPhysicalMemoryBacking::warn_available_space(size_t max) const {
// Note that the available space on a tmpfs or a hugetlbfs filesystem
// will be zero if no size limit was specified when it was mounted.
const size_t available = _file.available();
if (available == 0) {
// No size limit set, skip check
log_info(gc, init)("Available space on backing filesystem: N/A");
return;
}
log_info(gc, init)("Available space on backing filesystem: " SIZE_FORMAT "M", available / M);
// Warn if the filesystem doesn't currently have enough space available to hold
// the max heap size. The max heap size will be capped if we later hit this limit
// when trying to expand the heap.
if (available < max) {
log_warning(gc)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
log_warning(gc)("Not enough space available on the backing filesystem to hold the current max Java heap");
log_warning(gc)("size (" SIZE_FORMAT "M). Please adjust the size of the backing filesystem accordingly "
"(available", max / M);
log_warning(gc)("space is currently " SIZE_FORMAT "M). Continuing execution with the current filesystem "
"size could", available / M);
log_warning(gc)("lead to a premature OutOfMemoryError being thrown, due to failure to map memory.");
}
}
void ZPhysicalMemoryBacking::warn_max_map_count(size_t max) const {
const char* const filename = ZFILENAME_PROC_MAX_MAP_COUNT;
FILE* const file = fopen(filename, "r");
if (file == NULL) {
// Failed to open file, skip check
log_debug(gc, init)("Failed to open %s", filename);
return;
}
size_t actual_max_map_count = 0;
const int result = fscanf(file, SIZE_FORMAT, &actual_max_map_count);
fclose(file);
if (result != 1) {
// Failed to read file, skip check
log_debug(gc, init)("Failed to read %s", filename);
return;
}
// The required max map count is impossible to calculate exactly since subsystems
// other than ZGC are also creating memory mappings, and we have no control over that.
// However, ZGC tends to create the most mappings and dominate the total count.
// In the worst cases, ZGC will map each granule three times, i.e. once per heap view.
// We speculate that we need another 20% to allow for non-ZGC subsystems to map memory.
const size_t required_max_map_count = (max / ZGranuleSize) * 3 * 1.2;
if (actual_max_map_count < required_max_map_count) {
log_warning(gc)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
log_warning(gc)("The system limit on number of memory mappings per process might be too low for the given");
log_warning(gc)("max Java heap size (" SIZE_FORMAT "M). Please adjust %s to allow for at",
max / M, filename);
log_warning(gc)("least " SIZE_FORMAT " mappings (current limit is " SIZE_FORMAT "). Continuing execution "
"with the current", required_max_map_count, actual_max_map_count);
log_warning(gc)("limit could lead to a fatal error, due to failure to map memory.");
}
}
void ZPhysicalMemoryBacking::warn_commit_limits(size_t max) const {
// Warn if available space is too low
warn_available_space(max);
// Warn if max map count is too low
warn_max_map_count(max);
}
bool ZPhysicalMemoryBacking::supports_uncommit() {
assert(!is_init_completed(), "Invalid state");
assert(_file.size() >= ZGranuleSize, "Invalid size");
// Test if uncommit is supported by uncommitting and then re-committing a granule
return commit(uncommit(ZGranuleSize)) == ZGranuleSize;
}
size_t ZPhysicalMemoryBacking::commit(size_t size) {
size_t committed = 0;
// Fill holes in the backing file
while (committed < size) {
size_t allocated = 0;
const size_t remaining = size - committed;
const uintptr_t start = _uncommitted.alloc_from_front_at_most(remaining, &allocated);
if (start == UINTPTR_MAX) {
// No holes to commit
break;
}
// Try commit hole
const size_t filled = _file.commit(start, allocated);
if (filled > 0) {
// Successful or partialy successful
_committed.free(start, filled);
committed += filled;
}
if (filled < allocated) {
// Failed or partialy failed
_uncommitted.free(start + filled, allocated - filled);
return committed;
}
}
// Expand backing file
if (committed < size) {
const size_t remaining = size - committed;
const uintptr_t start = _file.size();
const size_t expanded = _file.commit(start, remaining);
if (expanded > 0) {
// Successful or partialy successful
_committed.free(start, expanded);
committed += expanded;
}
}
return committed;
}
size_t ZPhysicalMemoryBacking::uncommit(size_t size) {
size_t uncommitted = 0;
// Punch holes in backing file
while (uncommitted < size) {
size_t allocated = 0;
const size_t remaining = size - uncommitted;
const uintptr_t start = _committed.alloc_from_back_at_most(remaining, &allocated);
assert(start != UINTPTR_MAX, "Allocation should never fail");
// Try punch hole
const size_t punched = _file.uncommit(start, allocated);
if (punched > 0) {
// Successful or partialy successful
_uncommitted.free(start, punched);
uncommitted += punched;
}
if (punched < allocated) {
// Failed or partialy failed
_committed.free(start + punched, allocated - punched);
return uncommitted;
}
}
return uncommitted;
}
ZPhysicalMemory ZPhysicalMemoryBacking::alloc(size_t size) {
assert(is_aligned(size, ZGranuleSize), "Invalid size");
ZPhysicalMemory pmem;
// Allocate segments
for (size_t allocated = 0; allocated < size; allocated += ZGranuleSize) {
const uintptr_t start = _committed.alloc_from_front(ZGranuleSize);
assert(start != UINTPTR_MAX, "Allocation should never fail");
pmem.add_segment(ZPhysicalMemorySegment(start, ZGranuleSize));
}
return pmem;
}
void ZPhysicalMemoryBacking::free(const ZPhysicalMemory& pmem) {
const size_t nsegments = pmem.nsegments();
// Free segments
for (size_t i = 0; i < nsegments; i++) {
const ZPhysicalMemorySegment& segment = pmem.segment(i);
_committed.free(segment.start(), segment.size());
}
}
void ZPhysicalMemoryBacking::map_failed(ZErrno err) const {
if (err == ENOMEM) {
fatal("Failed to map memory. Please check the system limit on number of "
"memory mappings allowed per process (see %s)", ZFILENAME_PROC_MAX_MAP_COUNT);
} else {
fatal("Failed to map memory (%s)", err.to_string());
}
}
void ZPhysicalMemoryBacking::advise_view(uintptr_t addr, size_t size, int advice) const {
if (madvise((void*)addr, size, advice) == -1) {
ZErrno err;
log_error(gc)("Failed to advise on memory (advice %d, %s)", advice, err.to_string());
}
}
void ZPhysicalMemoryBacking::pretouch_view(uintptr_t addr, size_t size) const {
const size_t page_size = ZLargePages::is_explicit() ? os::large_page_size() : os::vm_page_size();
os::pretouch_memory((void*)addr, (void*)(addr + size), page_size);
}
void ZPhysicalMemoryBacking::map_view(const ZPhysicalMemory& pmem, uintptr_t addr, bool pretouch) const {
const size_t nsegments = pmem.nsegments();
size_t size = 0;
// Map segments
for (size_t i = 0; i < nsegments; i++) {
const ZPhysicalMemorySegment& segment = pmem.segment(i);
const uintptr_t segment_addr = addr + size;
const void* const res = mmap((void*)segment_addr, segment.size(), PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, _file.fd(), segment.start());
if (res == MAP_FAILED) {
ZErrno err;
map_failed(err);
}
size += segment.size();
}
// Advise on use of transparent huge pages before touching it
if (ZLargePages::is_transparent()) {
advise_view(addr, size, MADV_HUGEPAGE);
}
// NUMA interleave memory before touching it
ZNUMA::memory_interleave(addr, size);
// Pre-touch memory
if (pretouch) {
pretouch_view(addr, size);
}
}
void ZPhysicalMemoryBacking::unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
// Note that we must keep the address space reservation intact and just detach
// the backing memory. For this reason we map a new anonymous, non-accessible
// and non-reserved page over the mapping instead of actually unmapping.
const void* const res = mmap((void*)addr, pmem.size(), PROT_NONE, MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
if (res == MAP_FAILED) {
ZErrno err;
map_failed(err);
}
}
uintptr_t ZPhysicalMemoryBacking::nmt_address(uintptr_t offset) const {
// From an NMT point of view we treat the first heap view (marked0) as committed
return ZAddress::marked0(offset);
}
void ZPhysicalMemoryBacking::map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
if (ZVerifyViews) {
// Map good view
map_view(pmem, ZAddress::good(offset), AlwaysPreTouch);
} else {
// Map all views
map_view(pmem, ZAddress::marked0(offset), AlwaysPreTouch);
map_view(pmem, ZAddress::marked1(offset), AlwaysPreTouch);
map_view(pmem, ZAddress::remapped(offset), AlwaysPreTouch);
}
}
void ZPhysicalMemoryBacking::unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
if (ZVerifyViews) {
// Unmap good view
unmap_view(pmem, ZAddress::good(offset));
} else {
// Unmap all views
unmap_view(pmem, ZAddress::marked0(offset));
unmap_view(pmem, ZAddress::marked1(offset));
unmap_view(pmem, ZAddress::remapped(offset));
}
}
void ZPhysicalMemoryBacking::debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
// Map good view
assert(ZVerifyViews, "Should be enabled");
map_view(pmem, ZAddress::good(offset), false /* pretouch */);
}
void ZPhysicalMemoryBacking::debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
// Unmap good view
assert(ZVerifyViews, "Should be enabled");
unmap_view(pmem, ZAddress::good(offset));
}