3c508b38a2
This relands commit3f4e9bbe43. which was a reland ofc4a062a958which was a reland of28a30c578cwhich was a reland of5d7a29c90eThe change had an issue that embedders implementing heap tracing (e.g. Unified Heap with Blink) could be passed an uninitialized pointer if marking happened during deserialization of an object containing such a pointer. Because of the 0xdeadbed0 uninitialized filler value, these embedders would then receive the value 0xdeadbed0deadbed0 as the 'pointer', and crash on dereference. There is, however, special handling already for null pointers in heap tracing, also for dealing with not-yet initialized values. So, we can make the uninitialized Smi filler be 0x00000000, and that will make such embedded fields have a nullptr representation, making them follow the normal uninitialized value bailouts. In addition, it relands the following dependent changes, which are relanding unchanged and are followup performance improvements. Relanding them in the same change should allow for cleaner reverts should they be needed. This relands commit76ad3ab597[identity-map] Change resize heuristic This relands commit77cc96aa48[identity-map] Cache the calculated Hash This relands commitbee5b996aa[serializer] Remove Deserializer::Initialize This relands commitc8f73f2266[serializer] Cache instance type in PostProcessNewObject This relands commit4e7c99abda[identity-map] Remove double-lookups in IdentityMap Original change's description: > Reland^3 "[serializer] Allocate during deserialization" > > This is a reland ofc4a062a958> which was a reland of28a30c578c> which was a reland of5d7a29c90e> > Fixes TSAN errors from non-atomic writes in the deserializer. Now all > writes are (relaxed) atomic. > > Original change's description: > > Reland^2 "[serializer] Allocate during deserialization" > > > > This is a reland of28a30c578c> > which was a reland of5d7a29c90e> > > > The crashes were from calling RegisterDeserializerFinished on a null > > Isolate pointer, for a deserializer that was never initialised > > (specifically, ReadOnlyDeserializer when ROHeap is shared). > > > > Original change's description: > > > Reland "[serializer] Allocate during deserialization" > > > > > > This is a reland of5d7a29c90e> > > > > > This reland shuffles around the order of checks in Heap::AllocateRawWith > > > to not check the new space addresses until it's known that this is a new > > > space allocation. This fixes an UBSan failure during read-only space > > > deserialization, which happens before the new space is initialized. > > > > > > It also fixes some issues discovered by --stress-snapshot, around > > > serializing ThinStrings (which are now elided as part of serialization), > > > handle counts (I bumped the maximum handle count in that check), and > > > clearing map transitions (the map backpointer field needed a Smi > > > uninitialized value check). > > > > > > Original change's description: > > > > [serializer] Allocate during deserialization > > > > > > > > This patch removes the concept of reservations and a specialized > > > > deserializer allocator, and instead makes the deserializer allocate > > > > directly with the Heap's Allocate method. > > > > > > > > The major consequence of this is that the GC can now run during > > > > deserialization, which means that: > > > > > > > > a) Deserialized objects are visible to the GC, and > > > > b) Objects that the deserializer/deserialized objects point to can > > > > move. > > > > > > > > Point a) is mostly not a problem due to previous work in making > > > > deserialized objects "GC valid", i.e. making sure that they have a valid > > > > size before any subsequent allocation/safepoint. We now additionally > > > > have to initialize the allocated space with a valid tagged value -- this > > > > is a magic Smi value to keep "uninitialized" checks simple. > > > > > > > > Point b) is solved by Handlifying the deserializer. This involves > > > > changing any vectors of objects into vectors of Handles, and any object > > > > keyed map into an IdentityMap (we can't use Handles as keys because > > > > the object's address is no longer a stable hash). > > > > > > > > Back-references can no longer be direct chunk offsets, so instead the > > > > deserializer stores a Handle to each deserialized object, and the > > > > backreference is an index into this handle array. This encoding could > > > > be optimized in the future with e.g. a second pass over the serialized > > > > array which emits a different bytecode for objects that are and aren't > > > > back-referenced. > > > > > > > > Additionally, the slot-walk over objects to initialize them can no > > > > longer use absolute slot offsets, as again an object may move and its > > > > slot address would become invalid. Now, slots are walked as relative > > > > offsets to a Handle to the object, or as absolute slots for the case of > > > > root pointers. A concept of "slot accessor" is introduced to share the > > > > code between these two modes, and writing the slot (including write > > > > barriers) is abstracted into this accessor. > > > > > > > > Finally, the Code body walk is modified to deserialize all objects > > > > referred to by RelocInfos before doing the RelocInfo walk itself. This > > > > is because RelocInfoIterator uses raw pointers, so we cannot allocate > > > > during a RelocInfo walk. > > > > > > > > As a drive-by, the VariableRawData bytecode is tweaked to use tagged > > > > size rather than byte size -- the size is expected to be tagged-aligned > > > > anyway, so now we get an extra few bits in the size encoding. > > > > > > > > Bug: chromium:1075999 > > > > Change-Id: I672c42f553f2669888cc5e35d692c1b8ece1845e > > > > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2404451 > > > > Commit-Queue: Leszek Swirski <leszeks@chromium.org> > > > > Reviewed-by: Jakob Gruber <jgruber@chromium.org> > > > > Reviewed-by: Ulan Degenbaev <ulan@chromium.org> > > > > Cr-Commit-Position: refs/heads/master@{#70229} Bug: chromium:1075999 Change-Id: Ib514a4ef16bd02bfb60d046ecbf8fae1ead64a98 Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2452689 Commit-Queue: Leszek Swirski <leszeks@chromium.org> Reviewed-by: Ulan Degenbaev <ulan@chromium.org> Reviewed-by: Jakob Gruber <jgruber@chromium.org> Cr-Commit-Position: refs/heads/master@{#70366}
45 lines
1.2 KiB
JSON
45 lines
1.2 KiB
JSON
{
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"owners": ["yangguo@chromium.org", "jgruber@chromium.org"],
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"name": "Memory",
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"run_count": 5,
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"units": "bytes",
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"resources": ["run.js"],
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"main": "run.js",
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"path": ["."],
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"flags": ["--allow-natives-syntax", "--profile-deserialization"],
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"tests": [
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{
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"name": "ReservedMemoryIsolate",
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"results_regexp": "(\\d+) bytes per isolate$"
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"name": "SnapshotSizeStartup",
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"name": "SnapshotSizeReadOnly",
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"name": "SnapshotSizeContext",
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},
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"name": "DeserializationTimeIsolate",
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},
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{
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"name": "DeserializationTimeContext",
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"results_regexp": "\\[Deserializing context #0 \\(\\d+ bytes\\) took ([\\d.]+) ms\\]"
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},
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{
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"name": "EmbeddedBuiltinsSize",
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}
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]
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}
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