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/*
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* Copyright (c) 2015, 2019, Oracle and/or its affiliates. All rights reserved.
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
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*
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* This code is free software; you can redistribute it and/or modify it
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* under the terms of the GNU General Public License version 2 only, as
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* published by the Free Software Foundation.
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*
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* This code is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
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* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
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* version 2 for more details (a copy is included in the LICENSE file that
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* accompanied this code).
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*
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* You should have received a copy of the GNU General Public License version
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* 2 along with this work; if not, write to the Free Software Foundation,
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* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
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* or visit www.oracle.com if you need additional information or have any
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* questions.
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*/
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#include "precompiled.hpp"
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#include "gc/z/zAddress.inline.hpp"
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#include "gc/z/zBackingFile_linux_aarch64.hpp"
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#include "gc/z/zErrno.hpp"
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#include "gc/z/zGlobals.hpp"
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#include "gc/z/zLargePages.inline.hpp"
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#include "gc/z/zMemory.hpp"
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#include "gc/z/zNUMA.hpp"
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#include "gc/z/zPhysicalMemory.inline.hpp"
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#include "gc/z/zPhysicalMemoryBacking_linux_aarch64.hpp"
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#include "logging/log.hpp"
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#include "runtime/init.hpp"
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#include "runtime/os.hpp"
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#include "utilities/align.hpp"
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#include "utilities/debug.hpp"
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#include <stdio.h>
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#include <sys/mman.h>
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#include <sys/types.h>
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//
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// Support for building on older Linux systems
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//
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// madvise(2) flags
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#ifndef MADV_HUGEPAGE
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#define MADV_HUGEPAGE 14
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#endif
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// Proc file entry for max map mount
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#define ZFILENAME_PROC_MAX_MAP_COUNT "/proc/sys/vm/max_map_count"
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bool ZPhysicalMemoryBacking::is_initialized() const {
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return _file.is_initialized();
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}
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void ZPhysicalMemoryBacking::warn_available_space(size_t max) const {
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// Note that the available space on a tmpfs or a hugetlbfs filesystem
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// will be zero if no size limit was specified when it was mounted.
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const size_t available = _file.available();
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if (available == 0) {
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// No size limit set, skip check
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log_info(gc, init)("Available space on backing filesystem: N/A");
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return;
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}
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log_info(gc, init)("Available space on backing filesystem: " SIZE_FORMAT "M", available / M);
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// Warn if the filesystem doesn't currently have enough space available to hold
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// the max heap size. The max heap size will be capped if we later hit this limit
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// when trying to expand the heap.
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if (available < max) {
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log_warning(gc)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
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log_warning(gc)("Not enough space available on the backing filesystem to hold the current max Java heap");
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log_warning(gc)("size (" SIZE_FORMAT "M). Please adjust the size of the backing filesystem accordingly "
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"(available", max / M);
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log_warning(gc)("space is currently " SIZE_FORMAT "M). Continuing execution with the current filesystem "
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"size could", available / M);
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log_warning(gc)("lead to a premature OutOfMemoryError being thrown, due to failure to map memory.");
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}
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}
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void ZPhysicalMemoryBacking::warn_max_map_count(size_t max) const {
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const char* const filename = ZFILENAME_PROC_MAX_MAP_COUNT;
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FILE* const file = fopen(filename, "r");
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if (file == NULL) {
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// Failed to open file, skip check
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log_debug(gc, init)("Failed to open %s", filename);
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return;
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}
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size_t actual_max_map_count = 0;
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const int result = fscanf(file, SIZE_FORMAT, &actual_max_map_count);
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fclose(file);
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if (result != 1) {
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// Failed to read file, skip check
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log_debug(gc, init)("Failed to read %s", filename);
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return;
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}
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// The required max map count is impossible to calculate exactly since subsystems
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// other than ZGC are also creating memory mappings, and we have no control over that.
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// However, ZGC tends to create the most mappings and dominate the total count.
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// In the worst cases, ZGC will map each granule three times, i.e. once per heap view.
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// We speculate that we need another 20% to allow for non-ZGC subsystems to map memory.
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const size_t required_max_map_count = (max / ZGranuleSize) * 3 * 1.2;
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if (actual_max_map_count < required_max_map_count) {
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log_warning(gc)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
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log_warning(gc)("The system limit on number of memory mappings per process might be too low for the given");
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log_warning(gc)("max Java heap size (" SIZE_FORMAT "M). Please adjust %s to allow for at",
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max / M, filename);
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log_warning(gc)("least " SIZE_FORMAT " mappings (current limit is " SIZE_FORMAT "). Continuing execution "
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"with the current", required_max_map_count, actual_max_map_count);
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log_warning(gc)("limit could lead to a fatal error, due to failure to map memory.");
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}
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}
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void ZPhysicalMemoryBacking::warn_commit_limits(size_t max) const {
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// Warn if available space is too low
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warn_available_space(max);
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// Warn if max map count is too low
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warn_max_map_count(max);
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}
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bool ZPhysicalMemoryBacking::supports_uncommit() {
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assert(!is_init_completed(), "Invalid state");
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assert(_file.size() >= ZGranuleSize, "Invalid size");
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// Test if uncommit is supported by uncommitting and then re-committing a granule
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return commit(uncommit(ZGranuleSize)) == ZGranuleSize;
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}
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size_t ZPhysicalMemoryBacking::commit(size_t size) {
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size_t committed = 0;
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// Fill holes in the backing file
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while (committed < size) {
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size_t allocated = 0;
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const size_t remaining = size - committed;
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const uintptr_t start = _uncommitted.alloc_from_front_at_most(remaining, &allocated);
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if (start == UINTPTR_MAX) {
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// No holes to commit
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break;
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}
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// Try commit hole
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const size_t filled = _file.commit(start, allocated);
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if (filled > 0) {
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// Successful or partialy successful
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_committed.free(start, filled);
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committed += filled;
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}
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if (filled < allocated) {
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// Failed or partialy failed
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_uncommitted.free(start + filled, allocated - filled);
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return committed;
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}
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}
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// Expand backing file
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if (committed < size) {
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const size_t remaining = size - committed;
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const uintptr_t start = _file.size();
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const size_t expanded = _file.commit(start, remaining);
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if (expanded > 0) {
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// Successful or partialy successful
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_committed.free(start, expanded);
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committed += expanded;
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}
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}
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return committed;
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}
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size_t ZPhysicalMemoryBacking::uncommit(size_t size) {
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size_t uncommitted = 0;
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// Punch holes in backing file
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while (uncommitted < size) {
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size_t allocated = 0;
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const size_t remaining = size - uncommitted;
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const uintptr_t start = _committed.alloc_from_back_at_most(remaining, &allocated);
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assert(start != UINTPTR_MAX, "Allocation should never fail");
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// Try punch hole
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const size_t punched = _file.uncommit(start, allocated);
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if (punched > 0) {
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// Successful or partialy successful
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_uncommitted.free(start, punched);
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uncommitted += punched;
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}
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if (punched < allocated) {
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// Failed or partialy failed
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_committed.free(start + punched, allocated - punched);
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return uncommitted;
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}
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}
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return uncommitted;
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}
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ZPhysicalMemory ZPhysicalMemoryBacking::alloc(size_t size) {
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assert(is_aligned(size, ZGranuleSize), "Invalid size");
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ZPhysicalMemory pmem;
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// Allocate segments
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for (size_t allocated = 0; allocated < size; allocated += ZGranuleSize) {
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const uintptr_t start = _committed.alloc_from_front(ZGranuleSize);
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assert(start != UINTPTR_MAX, "Allocation should never fail");
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pmem.add_segment(ZPhysicalMemorySegment(start, ZGranuleSize));
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}
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return pmem;
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}
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void ZPhysicalMemoryBacking::free(const ZPhysicalMemory& pmem) {
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const size_t nsegments = pmem.nsegments();
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// Free segments
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for (size_t i = 0; i < nsegments; i++) {
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const ZPhysicalMemorySegment& segment = pmem.segment(i);
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_committed.free(segment.start(), segment.size());
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}
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}
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void ZPhysicalMemoryBacking::map_failed(ZErrno err) const {
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if (err == ENOMEM) {
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fatal("Failed to map memory. Please check the system limit on number of "
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"memory mappings allowed per process (see %s)", ZFILENAME_PROC_MAX_MAP_COUNT);
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} else {
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fatal("Failed to map memory (%s)", err.to_string());
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}
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}
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void ZPhysicalMemoryBacking::advise_view(uintptr_t addr, size_t size, int advice) const {
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if (madvise((void*)addr, size, advice) == -1) {
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ZErrno err;
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log_error(gc)("Failed to advise on memory (advice %d, %s)", advice, err.to_string());
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}
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}
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void ZPhysicalMemoryBacking::pretouch_view(uintptr_t addr, size_t size) const {
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const size_t page_size = ZLargePages::is_explicit() ? os::large_page_size() : os::vm_page_size();
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os::pretouch_memory((void*)addr, (void*)(addr + size), page_size);
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}
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void ZPhysicalMemoryBacking::map_view(const ZPhysicalMemory& pmem, uintptr_t addr, bool pretouch) const {
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const size_t nsegments = pmem.nsegments();
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size_t size = 0;
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// Map segments
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for (size_t i = 0; i < nsegments; i++) {
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const ZPhysicalMemorySegment& segment = pmem.segment(i);
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const uintptr_t segment_addr = addr + size;
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const void* const res = mmap((void*)segment_addr, segment.size(), PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, _file.fd(), segment.start());
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if (res == MAP_FAILED) {
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ZErrno err;
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map_failed(err);
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}
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size += segment.size();
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}
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// Advise on use of transparent huge pages before touching it
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if (ZLargePages::is_transparent()) {
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advise_view(addr, size, MADV_HUGEPAGE);
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}
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// NUMA interleave memory before touching it
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ZNUMA::memory_interleave(addr, size);
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// Pre-touch memory
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if (pretouch) {
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pretouch_view(addr, size);
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}
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}
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void ZPhysicalMemoryBacking::unmap_view(const ZPhysicalMemory& pmem, uintptr_t addr) const {
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// Note that we must keep the address space reservation intact and just detach
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// the backing memory. For this reason we map a new anonymous, non-accessible
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// and non-reserved page over the mapping instead of actually unmapping.
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const void* const res = mmap((void*)addr, pmem.size(), PROT_NONE, MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
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if (res == MAP_FAILED) {
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ZErrno err;
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map_failed(err);
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}
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}
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uintptr_t ZPhysicalMemoryBacking::nmt_address(uintptr_t offset) const {
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// From an NMT point of view we treat the first heap view (marked0) as committed
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return ZAddress::marked0(offset);
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}
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void ZPhysicalMemoryBacking::map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
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if (ZVerifyViews) {
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// Map good view
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map_view(pmem, ZAddress::good(offset), AlwaysPreTouch);
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} else {
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// Map all views
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map_view(pmem, ZAddress::marked0(offset), AlwaysPreTouch);
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map_view(pmem, ZAddress::marked1(offset), AlwaysPreTouch);
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map_view(pmem, ZAddress::remapped(offset), AlwaysPreTouch);
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}
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}
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void ZPhysicalMemoryBacking::unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
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if (ZVerifyViews) {
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// Unmap good view
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unmap_view(pmem, ZAddress::good(offset));
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} else {
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// Unmap all views
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unmap_view(pmem, ZAddress::marked0(offset));
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unmap_view(pmem, ZAddress::marked1(offset));
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unmap_view(pmem, ZAddress::remapped(offset));
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}
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}
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void ZPhysicalMemoryBacking::debug_map(const ZPhysicalMemory& pmem, uintptr_t offset) const {
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// Map good view
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assert(ZVerifyViews, "Should be enabled");
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map_view(pmem, ZAddress::good(offset), false /* pretouch */);
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}
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void ZPhysicalMemoryBacking::debug_unmap(const ZPhysicalMemory& pmem, uintptr_t offset) const {
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// Unmap good view
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assert(ZVerifyViews, "Should be enabled");
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unmap_view(pmem, ZAddress::good(offset));
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}
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