Dynamic generic dictionary expansion feature #32270

fadimounir · 2020-02-14T00:54:12Z

TODO:

Update JITInterface GUID in corinfo.h after JIT: Optimize "constant_string".Length #1378 (comment)

These changes introduce dynamic size expansion for generic dictionary layouts when we run out of slots.
The original implementation allowed for an expansion, but using a linked list structure, which made it
impossible to use fast lookup slots once we're out of slots in the first bucket.

This new implementation allows for the usage of fast lookup slots always, for all generic lookups.

This also removes the constraint we had on R2R, where we disabled the usage of fast slots all-together.

NOTE:
This is a much simpler implementation than the original commit which got reverted due to failures related to collectible assemblies (dotnet/coreclr#26262). The difference between these changes and the original ones is that dictionary expansion for types and methods is now done lazily, on-demand, whenever we attempt to read a value beyond the size of a given dictionary. This makes uses of the newly added JIT support from #31957. The bug with collectible assemblies have been also fixed, and I added a test to cover various interesting aspects of the feature.

BONUS:
Part of these changes is some cleanup work to really simplify the R2R dictionary access stubs. These stubs are now much more compact with fewer instructions and better registry usage (many #ifdef UNIX_AMD64_ABI blocks removed from the amd64 stub)

cc @dotnet/crossgen-contrib

src/coreclr/src/inc/corinfo.h

src/coreclr/src/jit/compiler.h

src/coreclr/src/inc/corinfo.h

src/coreclr/src/vm/genmeth.cpp

src/coreclr/src/vm/methodtable.cpp

jkotas · 2020-02-14T02:56:34Z

Overall, I like this much better than the original version. Thanks!

fadimounir · 2020-02-14T20:25:12Z

Couple of interesting benchmark numbers I tried:

Roslyn compiler, compiling Roslyn source code: 1~2% performance gain.
NewtonSoft serialization benchmark (found something on the web): 4% performance gain.

src/coreclr/src/vm/class.cpp

src/coreclr/src/vm/genericdict.h

src/coreclr/src/vm/generics.cpp

src/coreclr/src/vm/genericdict.cpp

src/coreclr/src/vm/generics.cpp

src/coreclr/src/vm/genericdict.cpp

src/coreclr/src/vm/jitinterface.cpp

src/coreclr/src/vm/method.hpp

src/coreclr/src/vm/methodtablebuilder.cpp

1) Separate dictionary layout expansion from dictionary expansions on types and methods 2) Dictionary expansions on types and methods done on-demand, after size checks by codegen (uses new JIT feature) 3) Update dependency tracking to only track derived types of base types with dictionaries 4) Update the R2R dictionary access stubs to perform size checks (and major cleanup there) 5) Fix loader allocator issue with the dependency tracking (bug in original implementation) 6) Add unit test 7) Update documentation

Update JIT interface guid

src/coreclr/src/vm/genericdict.cpp

jkotas

Thanks!

This reverts commit 7182559.

…otnet#33310) This reverts commit 7182559. (cherry picked from commit dca3429)

… (#33320) This reverts commit 7182559. (cherry picked from commit dca3429)

…#33343) * Revert "Revert "Dynamic generic dictionary expansion feature (#32270)" (#33310)" This reverts commit dca3429. * Fix race condition in dynamic dictionary resizing

Dotnet-GitSync-Bot added the area-System.Collections label Feb 14, 2020

fadimounir requested review from jkotas and davidwrighton February 14, 2020 00:54

jkoritzinsky added area-VM-coreclr and removed area-System.Collections labels Feb 14, 2020

jkotas requested changes Feb 14, 2020

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BruceForstall mentioned this pull request Feb 14, 2020

Optimize comparison of unknown type with a typeof #31686

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