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GeezerVison is showing github.com — src: do not enable wasm trap handler if there's not enough vmem · nodejs/node@79262ff

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  • doc/api
    • cli.md
  • src
    • debug_utils.h
    • node.cc
  • test
    • testpy
      • __init__.py
    • wasm-allocation
      • test-wasm-allocation-auto-adapt.js
      • test-wasm-allocation-disable-trap-handler.js
      • test-wasm-allocation-memory64.js
      • test-wasm-allocation.js
      • testcfg.py
      • wasm-allocation.status
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‎doc/api/cli.md‎

Copy file name to clipboardExpand all lines: doc/api/cli.md
+30-34Lines changed: 30 additions & 34 deletions
  • Display the source diff
  • Display the rich diff
Original file line numberDiff line numberDiff line change
@@ -754,40 +754,36 @@ vm.measureMemory();
754754
added:
755755
- v22.2.0
756756
- v20.15.0
757-
-->
758-
759-
By default, Node.js enables trap-handler-based WebAssembly bound
760-
checks. As a result, V8 does not need to insert inline bound checks
761-
in the code compiled from WebAssembly which may speed up WebAssembly
762-
execution significantly, but this optimization requires allocating
763-
a big virtual memory cage (currently 10GB). If the Node.js process
764-
does not have access to a large enough virtual memory address space
765-
due to system configurations or hardware limitations, users won't
766-
be able to run any WebAssembly that involves allocation in this
767-
virtual memory cage and will see an out-of-memory error.
768-
769-
```console
770-
$ ulimit -v 5000000
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$ node -p "new WebAssembly.Memory({ initial: 10, maximum: 100 });"
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[eval]:1
773-
new WebAssembly.Memory({ initial: 10, maximum: 100 });
774-
^
775-
776-
RangeError: WebAssembly.Memory(): could not allocate memory
777-
at [eval]:1:1
778-
at runScriptInThisContext (node:internal/vm:209:10)
779-
at node:internal/process/execution:118:14
780-
at [eval]-wrapper:6:24
781-
at runScript (node:internal/process/execution:101:62)
782-
at evalScript (node:internal/process/execution:136:3)
783-
at node:internal/main/eval_string:49:3
784-
785-
```
786-
787-
`--disable-wasm-trap-handler` disables this optimization so that
788-
users can at least run WebAssembly (with less optimal performance)
789-
when the virtual memory address space available to their Node.js
790-
process is lower than what the V8 WebAssembly memory cage needs.
757+
changes:
758+
- version:
759+
- REPLACEME
760+
pr-url: https://github.com/nodejs/node/pull/62132
761+
description: Node.js now automatically disables the trap handler when there is not
762+
enough virtual memory available at startup to allocate one cage.
763+
-->
764+
765+
Node.js enables V8's trap-handler-based WebAssembly bound checks on 64-bit platforms,
766+
which significantly improves WebAssembly performance by eliminating the need for
767+
inline bound checks. This optimization requires allocating a large virtual memory
768+
cage per WebAssembly memory instance (currently typically 8GB for 32-bit WebAssembly memory,
769+
16GB for 64-bit WebAssembly memory) to trap out-of-bound accesses. On most 64-bit
770+
platforms, the virtual memory address space is usually large enough (around 128TB)
771+
to accommodate typical WebAssembly usages, but if the machine has manual limits
772+
on virtual memory (e.g. through `ulimit -v`), WebAssembly memory allocation is
773+
more likely to fail with `WebAssembly.Memory(): could not allocate memory`.
774+
775+
At startup, Node.js automatically checks whether there is enough virtual memory
776+
available to allocate at least one cage, and if not, the trap-handler optimization
777+
is automatically disabled so that WebAssembly can still run using inline
778+
bound checks (with less optimal performance). But if the application needs to create
779+
many WebAssembly memory instances and the machine still configures a relatively high
780+
limit on virtual memory, allocation of WebAssembly memory instances may still fail
781+
more quickly than expected due to the raised virtual memory usage.
782+
783+
`--disable-wasm-trap-handler` fully disables this optimization so that WebAssembly memory
784+
instances always use inline bound checks instead of reserving large virtual memory cages.
785+
This allows more instances to be created when the virtual memory address space available
786+
to the Node.js process is limited.
791787

792788
### `--disallow-code-generation-from-strings`
793789

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‎src/debug_utils.h‎

Copy file name to clipboardExpand all lines: src/debug_utils.h
+1Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -44,6 +44,7 @@ void NODE_EXTERN_PRIVATE FWrite(FILE* file, const std::string& str);
4444
// from a provider type to a debug category.
4545
#define DEBUG_CATEGORY_NAMES(V) \
4646
NODE_ASYNC_PROVIDER_TYPES(V) \
47+
V(BOOTSTRAP) \
4748
V(CRYPTO) \
4849
V(COMPILE_CACHE) \
4950
V(DIAGNOSTICS) \
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‎src/node.cc‎

Copy file name to clipboardExpand all lines: src/node.cc
+42-1Lines changed: 42 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1046,6 +1046,45 @@ static ExitCode InitializeNodeWithArgsInternal(
10461046
return ExitCode::kNoFailure;
10471047
}
10481048

1049+
#if NODE_USE_V8_WASM_TRAP_HANDLER
1050+
bool CanEnableWebAssemblyTrapHandler() {
1051+
// On POSIX, the machine may have a limit on the amount of virtual memory
1052+
// available, if it's not enough to allocate at least one cage for WASM,
1053+
// then the trap-handler-based bound checks cannot be used.
1054+
#ifdef __POSIX__
1055+
struct rlimit lim;
1056+
if (getrlimit(RLIMIT_AS, &lim) != 0 || lim.rlim_cur == RLIM_INFINITY) {
1057+
// Can't get the limit or there's no limit, assume trap handler can be
1058+
// enabled.
1059+
return true;
1060+
}
1061+
uint64_t virtual_memory_available = static_cast<uint64_t>(lim.rlim_cur);
1062+
1063+
size_t byte_capacity = 64 * 1024; // 64KB, the minimum size of a WASM memory.
1064+
uint64_t cage_size_needed_32 = V8::GetWasmMemoryReservationSizeInBytes(
1065+
V8::WasmMemoryType::kMemory32, byte_capacity);
1066+
uint64_t cage_size_needed_64 = V8::GetWasmMemoryReservationSizeInBytes(
1067+
V8::WasmMemoryType::kMemory64, byte_capacity);
1068+
uint64_t cage_size_needed =
1069+
std::max(cage_size_needed_32, cage_size_needed_64);
1070+
bool can_enable = virtual_memory_available >= cage_size_needed;
1071+
per_process::Debug(DebugCategory::BOOTSTRAP,
1072+
"Virtual memory available: %" PRIu64 " bytes,\n"
1073+
"cage size needed for 32-bit: %" PRIu64 " bytes,\n"
1074+
"cage size needed for 64-bit: %" PRIu64 " bytes,\n"
1075+
"Can%senable WASM trap handler\n",
1076+
virtual_memory_available,
1077+
cage_size_needed_32,
1078+
cage_size_needed_64,
1079+
can_enable ? " " : " not ");
1080+
1081+
return can_enable;
1082+
#else
1083+
return true;
1084+
#endif // __POSIX__
1085+
}
1086+
#endif // NODE_USE_V8_WASM_TRAP_HANDLER
1087+
10491088
static std::shared_ptr<InitializationResultImpl>
10501089
InitializeOncePerProcessInternal(const std::vector<std::string>& args,
10511090
ProcessInitializationFlags::Flags flags =
@@ -1248,7 +1287,9 @@ InitializeOncePerProcessInternal(const std::vector<std::string>& args,
12481287
bool use_wasm_trap_handler =
12491288
!per_process::cli_options->disable_wasm_trap_handler;
12501289
if (!(flags & ProcessInitializationFlags::kNoDefaultSignalHandling) &&
1251-
use_wasm_trap_handler) {
1290+
use_wasm_trap_handler && CanEnableWebAssemblyTrapHandler()) {
1291+
per_process::Debug(DebugCategory::BOOTSTRAP,
1292+
"Enabling WebAssembly trap handler for bounds checks\n");
12521293
#if defined(_WIN32)
12531294
constexpr ULONG first = TRUE;
12541295
per_process::old_vectored_exception_handler =
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‎test/testpy/__init__.py‎

Copy file name to clipboardExpand all lines: test/testpy/__init__.py
+5-12Lines changed: 5 additions & 12 deletions
Original file line numberDiff line numberDiff line change
@@ -36,6 +36,7 @@
3636
LS_RE = re.compile(r'^test-.*\.m?js$')
3737
ENV_PATTERN = re.compile(r"//\s+Env:(.*)")
3838
NODE_TEST_PATTERN = re.compile(r"('|`|\")node:test\1")
39+
RLIMIT_AS_PATTERN = re.compile(r"//\s+RLIMIT_AS:\s*(\d+)")
3940

4041
class SimpleTestCase(test.TestCase):
4142

@@ -99,6 +100,10 @@ def GetRunConfiguration(self):
99100
else:
100101
result += flags
101102

103+
rlimit_as_match = RLIMIT_AS_PATTERN.search(source)
104+
if rlimit_as_match:
105+
self.max_virtual_memory = int(rlimit_as_match.group(1))
106+
102107
if self.context.use_error_reporter and NODE_TEST_PATTERN.search(source):
103108
result += ['--test-reporter=./test/common/test-error-reporter.js',
104109
'--test-reporter-destination=stdout']
@@ -189,15 +194,3 @@ def ListTests(self, current_path, path, arch, mode):
189194
for tst in result:
190195
tst.disable_core_files = True
191196
return result
192-
193-
class WasmAllocationTestConfiguration(SimpleTestConfiguration):
194-
def __init__(self, context, root, section, additional=None):
195-
super(WasmAllocationTestConfiguration, self).__init__(context, root, section,
196-
additional)
197-
198-
def ListTests(self, current_path, path, arch, mode):
199-
result = super(WasmAllocationTestConfiguration, self).ListTests(
200-
current_path, path, arch, mode)
201-
for tst in result:
202-
tst.max_virtual_memory = 5 * 1024 * 1024 * 1024 # 5GB
203-
return result
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‎test/wasm-allocation/test-wasm-allocation-auto-adapt.js‎

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+12Lines changed: 12 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,12 @@
1+
// RLIMIT_AS: 3221225472
2+
// When the virtual memory limit is 3GB, there is not enough virtual memory for
3+
// even one wasm cage. In this case Node.js should automatically adapt and
4+
// skip enabling trap-based bounds checks, so that WASM can at least run with
5+
// inline bound checks.
6+
'use strict';
7+
8+
require('../common');
9+
new WebAssembly.Memory({ initial: 10, maximum: 100 });
10+
11+
// Test memory64 works too.
12+
new WebAssembly.Memory({ address: 'i64', initial: 10n, maximum: 100n });
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‎test/wasm-allocation/test-wasm-allocation-disable-trap-handler.js‎

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+20Lines changed: 20 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,20 @@
1+
// Flags: --disable-wasm-trap-handler
2+
// RLIMIT_AS: 34359738368
3+
4+
// 32GB should be enough for at least 2 cages, but not enough for 30.
5+
6+
// Test that with limited virtual memory space, --disable-wasm-trap-handler
7+
// fully disables trap-based bounds checks, and thus allows WASM to run with
8+
// inline bound checks.
9+
'use strict';
10+
11+
require('../common');
12+
const instances = [];
13+
for (let i = 0; i < 30; i++) {
14+
instances.push(new WebAssembly.Memory({ initial: 10, maximum: 100 }));
15+
}
16+
17+
// Test memory64 works too.
18+
for (let i = 0; i < 30; i++) {
19+
instances.push(new WebAssembly.Memory({ initial: 10n, maximum: 100n, address: 'i64' }));
20+
}
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‎test/wasm-allocation/test-wasm-allocation-memory64.js‎

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+22Lines changed: 22 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,22 @@
1+
// RLIMIT_AS: 21474836480
2+
// With 20GB virtual memory, there's enough space for the first wasm memory64
3+
// allocation to succeed, but not enough for subsequent ones since each
4+
// wasm memory64 with guard regions reserves 16GB of virtual address space.
5+
'use strict';
6+
7+
require('../common');
8+
const assert = require('assert');
9+
10+
// The first allocation should succeed.
11+
const first = new WebAssembly.Memory({ address: 'i64', initial: 10n, maximum: 100n });
12+
assert(first);
13+
14+
// Subsequent allocations should eventually fail due to running out of
15+
// virtual address space. memory64 reserves 16GB per allocation (vs 8GB for
16+
// memory32), so the limit is reached even faster.
17+
assert.throws(() => {
18+
const instances = [first];
19+
for (let i = 1; i < 30; i++) {
20+
instances.push(new WebAssembly.Memory({ address: 'i64', initial: 10n, maximum: 100n }));
21+
}
22+
}, /WebAssembly\.Memory/);
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‎test/wasm-allocation/test-wasm-allocation.js‎

Copy file name to clipboardExpand all lines: test/wasm-allocation/test-wasm-allocation.js
+4-3Lines changed: 4 additions & 3 deletions
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,7 @@
1-
// Flags: --disable-wasm-trap-handler
2-
// Test that with limited virtual memory space, --disable-wasm-trap-handler
3-
// allows WASM to at least run with inline bound checks.
1+
// RLIMIT_AS: 21474836480
2+
// With 20GB virtual memory, there's enough space for the first few wasm memory
3+
// allocation to succeed, but not enough for many subsequent ones since each
4+
// wasm memory32 with guard regions reserves 8GB of virtual address space.
45
'use strict';
56

67
require('../common');
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‎test/wasm-allocation/testcfg.py‎

Copy file name to clipboardExpand all lines: test/wasm-allocation/testcfg.py
+1-1Lines changed: 1 addition & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,4 +3,4 @@
33
import testpy
44

55
def GetConfiguration(context, root):
6-
return testpy.WasmAllocationTestConfiguration(context, root, 'wasm-allocation')
6+
return testpy.SimpleTestConfiguration(context, root, 'wasm-allocation')
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‎test/wasm-allocation/wasm-allocation.status‎

Copy file name to clipboardExpand all lines: test/wasm-allocation/wasm-allocation.status
+6Lines changed: 6 additions & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -8,3 +8,9 @@ prefix wasm-allocation
88

99
[$system!=linux || $asan==on || $pointer_compression==on]
1010
test-wasm-allocation: SKIP
11+
test-wasm-allocation-auto-adapt: SKIP
12+
test-wasm-allocation-memory64: SKIP
13+
14+
[$arch!=x64 && $arch!=arm64]
15+
test-wasm-allocation: SKIP
16+
test-wasm-allocation-memory64: SKIP

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