Commit a11507e
src: stop copying code cache
The code cache is quite large - around 1.3 MiB. Change the code to use
non-owning buffers to avoid copying it. For starting up an otherwise
empty main isolate, this saves around 1.3 MiB of unique set size memory
(9.9 MiB -> 8.6 MiB) and 1.1ms elapsed time (22.9 ms -> 21.8 ms).
Copying the code cache is unnecessary since:
1. for the builtin snapshot, the code cache data has static lifetime.
2. for non-builtin snapshots, we create copies of the code cache data in
`SnapshotDeserializer::ReadVector`. These copies are owned by the
`Environment` (through `IsolateData` -> `SnapshotData`), so they
won't be deallocated.
3. a worker thread can copy a parent's isolate's code cache, but in that
case we still know that the parent isolate will outlive the worker
isolate.
(Admittedly point (2) feels a little fragile from a lifetime
perspective, and I would be happy to restrict this optimization to the
builtin snapshot.)
```console
$ perf stat -r 100 -e ... ./node -e 0
Performance counter stats for './node -e 0' (100 runs):
21.78 msec task-clock
2760 page-faults
113161604 instructions
18437648 branches
423230 branch-misses
853093 cache-references
41474 cache-misses
0.0225473 +- 0.0000504 seconds time elapsed ( +- 0.22% )
$ perf stat -r 100 -e ... ./node-main -e 0
Performance counter stats for './node-main -e 0' (100 runs):
22.91 msec task-clock
3102 page-faults
114890673 instructions
18751329 branches
428909 branch-misses
895721 cache-references
45202 cache-misses
0.0233760 +- 0.0000741 seconds time elapsed ( +- 0.32% )
```
PR-URL: #47144
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: Chengzhong Wu <legendecas@gmail.com>1 parent cad42e7 commit a11507e
2 files changed
Lines changed: 13 additions & 6 deletions
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
@@ -505,6 +505,9 @@ struct IsolateSettings { | |||
| 505 | 505 | // feature during the build step by passing the --disable-shared-readonly-heap | |
| 506 | 506 | // flag to the configure script. | |
| 507 | 507 | // | |
| 508 | + // The snapshot *must* be kept alive during the execution of the Isolate | ||
| 509 | + // that was created using it. | ||
| 510 | + // | ||
| 508 | 511 | // Snapshots are an *experimental* feature. In particular, the embedder API | |
| 509 | 512 | // exposed through this class is subject to change or removal between Node.js | |
| 510 | 513 | // versions, including possible API and ABI breakage. | |
| Original file line number | Diff line number | Diff line change | |
|---|---|---|---|
@@ -501,13 +501,17 @@ void BuiltinLoader::CopyCodeCache(std::vector<CodeCacheInfo>* out) const { | |||
| 501 | 501 | ||
| 502 | 502 | void BuiltinLoader::RefreshCodeCache(const std::vector<CodeCacheInfo>& in) { | |
| 503 | 503 | RwLock::ScopedLock lock(code_cache_->mutex); | |
| 504 | + code_cache_->map.reserve(in.size()); | ||
| 505 | + DCHECK(code_cache_->map.empty()); | ||
| 504 | 506 | for (auto const& item : in) { | |
| 505 | - size_t length = item.data.size(); | ||
| 506 | - uint8_t* buffer = new uint8_t[length]; | ||
| 507 | - memcpy(buffer, item.data.data(), length); | ||
| 508 | - auto new_cache = std::make_unique<v8::ScriptCompiler::CachedData>( | ||
| 509 | - buffer, length, v8::ScriptCompiler::CachedData::BufferOwned); | ||
| 510 | - code_cache_->map[item.id] = std::move(new_cache); | ||
| 507 | + auto result = code_cache_->map.emplace( | ||
| 508 | + item.id, | ||
| 509 | + std::make_unique<v8::ScriptCompiler::CachedData>( | ||
| 510 | + item.data.data(), | ||
| 511 | + item.data.size(), | ||
| 512 | + v8::ScriptCompiler::CachedData::BufferNotOwned)); | ||
| 513 | + USE(result.second); | ||
| 514 | + DCHECK(result.second); | ||
| 511 | 515 | } | |
| 512 | 516 | code_cache_->has_code_cache = true; | |
| 513 | 517 | } | |
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