• Adam Klein's avatar
    Revert "Reland^3 "[serializer] Allocate during deserialization"" · a10ec2be
    Adam Klein authored
    This reverts commit 3f4e9bbe, along
    with the following dependent changes (reverted to make this a clean revert):
    76ad3ab5 [identity-map] Change resize heuristic
    77cc96aa [identity-map] Cache the calculated Hash
    bee5b996 [serializer] Remove Deserializer::Initialize
    c8f73f22 [serializer] Cache instance type in PostProcessNewObject
    4e7c99ab [identity-map] Remove double-lookups in IdentityMap
    
    Reason for revert: major crash spike on Canary (https://crbug.com/1135027)
    
    Original change's description:
    > Reland^3 "[serializer] Allocate during deserialization"
    >
    > This is a reland of c4a062a9
    > which was a reland of 28a30c57
    > which was a reland of 5d7a29c9
    >
    > 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 of 28a30c57
    > > which was a reland of 5d7a29c9
    > >
    > > 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 of 5d7a29c9
    > > >
    > > > 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: Ibc77cc48b3440b4a28b09746cfc47e50c340ce54
    > > > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2440828
    > > > Commit-Queue: Leszek Swirski <leszeks@chromium.org>
    > > > Auto-Submit: 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@{#70267}
    > >
    > > Tbr: jgruber@chromium.org,ulan@chromium.org
    > > Bug: chromium:1075999
    > > Change-Id: Iaa8dc54895866ada0e34a7c9e8fff9ae1cb13f2d
    > > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2444991
    > > Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
    > > Commit-Queue: Leszek Swirski <leszeks@chromium.org>
    > > Cr-Commit-Position: refs/heads/master@{#70279}
    >
    > Tbr: jgruber@chromium.org,ulan@chromium.org
    > Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel_ng,v8_linux64_tsan_no_cm_rel_ng,v8_linux64_tsan_isolates_rel_ng
    > Bug: chromium:1075999
    > Change-Id: I0b9b11644aebc4cc8b07c62a0f765b24e4d73d89
    > Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2445872
    > Commit-Queue: Leszek Swirski <leszeks@chromium.org>
    > Auto-Submit: Leszek Swirski <leszeks@chromium.org>
    > Reviewed-by: Dominik Inführ <dinfuehr@chromium.org>
    > Cr-Commit-Position: refs/heads/master@{#70288}
    
    TBR=ulan@chromium.org,jgruber@chromium.org,leszeks@chromium.org,dinfuehr@chromium.org
    
    Bug: chromium:1075999, chromium:1135027
    Change-Id: I5d0d9e49c0302d94ff7291834f5f18e7a0839eb7
    Cq-Include-Trybots: luci.v8.try:v8_linux64_tsan_rel_ng,v8_linux64_tsan_no_cm_rel_ng,v8_linux64_tsan_isolates_rel_ng
    Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2451030Reviewed-by: 's avatarAdam Klein <adamk@chromium.org>
    Commit-Queue: Adam Klein <adamk@chromium.org>
    Cr-Commit-Position: refs/heads/master@{#70328}
    a10ec2be
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