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src/hotspot/os_cpu/linux_x86/gc/z/zPhysicalMemoryBacking_linux_x86.cpp
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@@ -30,42 +30,62 @@
#include "gc/z/zMemory.hpp"
#include "gc/z/zNUMA.hpp"
#include "gc/z/zPhysicalMemory.inline.hpp"
#include "gc/z/zPhysicalMemoryBacking_linux_x86.hpp"
#include "logging/log.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"
-ZPhysicalMemoryBacking::ZPhysicalMemoryBacking(size_t max_capacity) :
- _manager(),
- _file() {
+bool ZPhysicalMemoryBacking::is_initialized() const {
+ return _file.is_initialized();
+}
- if (!_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;
}
- // Check and warn if max map count is too low
- check_max_map_count(max_capacity);
+ log_info(gc, init)("Available space on backing filesystem: " SIZE_FORMAT "M", available / M);
- // Check and warn if available space on filesystem is too low
- check_available_space_on_filesystem(max_capacity);
+ // 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::check_max_map_count(size_t max_capacity) const {
+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);
@@ -84,90 +104,129 @@
// 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_capacity / ZGranuleSize) * 3 * 1.2;
+ const size_t required_max_map_count = (max / ZGranuleSize) * 3 * 1.2;
if (actual_max_map_count < required_max_map_count) {
- log_warning(gc, init)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
- log_warning(gc, init)("The system limit on number of memory mappings per process might be too low "
- "for the given");
- log_warning(gc, init)("max Java heap size (" SIZE_FORMAT "M). Please adjust %s to allow for at",
- max_capacity / M, filename);
- log_warning(gc, init)("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, init)("limit could lead to a fatal error, due to failure to map memory.");
+ 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::check_available_space_on_filesystem(size_t max_capacity) 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;
- }
+void ZPhysicalMemoryBacking::warn_commit_limits(size_t max) const {
+ // Warn if available space is too low
+ warn_available_space(max);
- log_info(gc, init)("Available space on backing filesystem: " SIZE_FORMAT "M",
- available / M);
+ // Warn if max map count is too low
+ warn_max_map_count(max);
+}
- // 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_capacity) {
- log_warning(gc, init)("***** WARNING! INCORRECT SYSTEM CONFIGURATION DETECTED! *****");
- log_warning(gc, init)("Not enough space available on the backing filesystem to hold the current "
- "max Java heap");
- log_warning(gc, init)("size (" SIZE_FORMAT "M). Please adjust the size of the backing filesystem "
- "accordingly (available", max_capacity / M);
- log_warning(gc, init)("space is currently " SIZE_FORMAT "M). Continuing execution with the current "
- "filesystem size could", available / M);
- log_warning(gc, init)("lead to a premature OutOfMemoryError being thrown, due to failure to map "
- "memory.");
- }
+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;
}
-bool ZPhysicalMemoryBacking::is_initialized() const {
- return _file.is_initialized();
+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::try_expand(size_t old_capacity, size_t new_capacity) {
- assert(old_capacity < new_capacity, "Invalid old/new capacity");
+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");
- const size_t capacity = _file.try_expand(old_capacity, new_capacity - old_capacity, ZGranuleSize);
- if (capacity > old_capacity) {
- // Add expanded capacity to free list
- _manager.free(old_capacity, capacity - old_capacity);
+ // 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 capacity;
+ 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 = _manager.alloc_from_front(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(ZPhysicalMemory 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);
- _manager.free(segment.start(), segment.size());
+ const ZPhysicalMemorySegment& segment = pmem.segment(i);
+ _committed.free(segment.start(), segment.size());
}
}
void ZPhysicalMemoryBacking::map_failed(ZErrno err) const {
if (err == ENOMEM) {
@@ -176,69 +235,70 @@
} else {
fatal("Failed to map memory (%s)", err.to_string());
}
}
-void ZPhysicalMemoryBacking::advise_view(uintptr_t addr, size_t size) const {
- if (madvise((void*)addr, size, MADV_HUGEPAGE) == -1) {
+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 use of transparent huge pages (%s)", err.to_string());
+ 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(ZPhysicalMemory pmem, uintptr_t addr, bool pretouch) const {
+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 size_t size = segment.size();
- const void* const res = mmap((void*)addr, size, PROT_READ|PROT_WRITE, MAP_FIXED|MAP_SHARED, _file.fd(), segment.start());
+ 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);
}
- // Advise on use of transparent huge pages before touching it
- if (ZLargePages::is_transparent()) {
- advise_view(addr, size);
- }
+ size += segment.size();
+ }
- // NUMA interleave memory before touching it
- ZNUMA::memory_interleave(addr, size);
+ // Advise on use of transparent huge pages before touching it
+ if (ZLargePages::is_transparent()) {
+ advise_view(addr, size, MADV_HUGEPAGE);
+ }
- if (pretouch) {
- pretouch_view(addr, size);
- }
+ // NUMA interleave memory before touching it
+ ZNUMA::memory_interleave(addr, size);
- addr += size;
+ // Pre-touch memory
+ if (pretouch) {
+ pretouch_view(addr, size);
}
}
-void ZPhysicalMemoryBacking::unmap_view(ZPhysicalMemory pmem, uintptr_t addr) const {
+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 size_t size = pmem.size();
- const void* const res = mmap((void*)addr, size, PROT_NONE, MAP_FIXED|MAP_ANONYMOUS|MAP_PRIVATE|MAP_NORESERVE, -1, 0);
+ 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 mapping (marked0) as committed
+ // From an NMT point of view we treat the first heap view (marked0) as committed
return ZAddress::marked0(offset);
}
-void ZPhysicalMemoryBacking::map(ZPhysicalMemory pmem, uintptr_t offset) const {
+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
@@ -246,11 +306,11 @@
map_view(pmem, ZAddress::marked1(offset), AlwaysPreTouch);
map_view(pmem, ZAddress::remapped(offset), AlwaysPreTouch);
}
}
-void ZPhysicalMemoryBacking::unmap(ZPhysicalMemory pmem, uintptr_t offset) const {
+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
@@ -258,16 +318,16 @@
unmap_view(pmem, ZAddress::marked1(offset));
unmap_view(pmem, ZAddress::remapped(offset));
}
}
-void ZPhysicalMemoryBacking::debug_map(ZPhysicalMemory pmem, uintptr_t offset) const {
+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(ZPhysicalMemory pmem, uintptr_t offset) const {
+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));
}
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