Optimize shared memory operations

[ludfjig]

Should speed up memory-heavy things in hyperlight such as restoring snapshots, copying memory parameters, etc. u128 proved to be faster than u64.

Inspired by postgres.

[Copilot]

Pull request overview

This PR optimizes shared memory operations in Hyperlight by implementing chunked aligned memory access using u128 (16-byte) operations, significantly improving performance for memory-heavy operations like snapshot restoration and parameter copying. The optimization is inspired by PostgreSQL's memory handling techniques.

Changes:

• Replaced byte-by-byte memory operations with aligned u128 chunk processing
• Added comprehensive benchmarks for shared memory operations (fill, copy_to_slice, copy_from_slice)
• Implemented three-phase approach: handle unaligned head bytes, process aligned chunks, handle remaining tail bytes

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 6 comments.

File	Description
src/hyperlight_host/src/mem/shared_mem.rs	Optimized copy_to_slice, copy_from_slice, and fill methods with aligned u128 chunk operations
src/hyperlight_host/benches/benchmarks.rs	Added new benchmark suite for shared memory operations with 1MB and 64MB test sizes

[Copilot]

Pull request overview

Copilot reviewed 2 out of 2 changed files in this pull request and generated no new comments.

[andreiltd]

Nice speed up!

My first instinct looking at the patch was that we should be using: https://doc.rust-lang.org/std/primitive.slice.html#method.align_to to divide mem into aligned slices, but then for shared memory we actually need to iterate over raw pointers to use volatile semantics and using slices will make it a bit more annoying. We could still use it for fill method but I see the value in keeping all the functions similar :)

[ludfjig]

Nice speed up!

My first instinct looking at the patch was that we should be using: https://doc.rust-lang.org/std/primitive.slice.html#method.align_to to divide mem into aligned slices, but then for shared memory we actually need to iterate over raw pointers to use volatile semantics and using slices will make it a bit more annoying. We could still use it for fill method but I see the value in keeping all the functions similar :)

I also thought of using align_to for all of these in the beginning, and actually used it in fill, but decided against it because it was not as clean as I hoped.