Zero copy for send

[ice1000]

TODOs

• Fix benchmark compilation
• Fix link error (multiple symbol definitions)
• Fix size_t 6 in Rust becomes size_t in C 140184721559552 via FFI (140184721559552+6 is 2^47)
• Sync master changes
• Improve GrpcSlice
• Improve GrpcByteBuffer
• (New!) Support bytes in prost

Now (updated at: 23, April 2019)

Since @nrc has introduced prost support (instead of rust-protobuf) which is natively using "bytes", we no longer have that one copy for send which is stated to be necessary below.
Yay!

Before:

• User code deserialize (particularly, the protobuf library), producing a list of &[u8], we copied the data into a Vec<u8>, this is done internally in the protobuf library (copy 0)
• We create a grpc_slice (a ref-counted single string) by copying the Vec<u8> mentioned above (copy 1)
• We create a grpc_byte_buffer (a ref-counted list of strings) from only one grpc_slice
• Send

Total copy: 2

After:

• User code deserialize (particularly, the protobuf library), producing a list of &[u8], we copied each produced &[u8] and collect them into a grpc_byte_buffer (copy 0)
• Send

Total copy: 1

The reason why still one copy:

• Rust manages its own allocated memory'a lifetime
• C-side uses a ref-count mechanism to manage the lifetime of objects
• We either need to longer the Rust objects' lifetime or copy once
• Tried to longer Rust objects' lifetime in Zero copy for send #225
  • Result: grpc supports buffer-hint which requires a much longer lifetime, it's too hard to manage the lifetime in such case
  • This is why I closed Zero copy for send #225

[ice1000]

@overvenus PTAL

[ice1000]

Writing down some notes

[ice1000]

Tests fixed, please review @overvenus @BusyJay

[ice1000]

error: item `call::MessageWriter` has a public `len` method but no corresponding `is_empty` method
   --> src/call/mod.rs:123:1
    |
123 | / impl MessageWriter {
124 | |     pub fn new() -> MessageWriter {
125 | |         MessageWriter {
126 | |             data: Vec::new(),
...   |
147 | |     }
148 | | }
    | |_^
    |
    = note: `-D clippy::len-without-is-empty` implied by `-D warnings`
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#len_without_is_empty
error: using `clone` on a `Copy` type
   --> src/call/mod.rs:134:44
    |
134 |                 grpc_sys::grpc_slice_unref(slice.clone());
    |                                            ^^^^^^^^^^^^^ help: try dereferencing it: `*slice`
    |
    = note: `-D clippy::clone-on-copy` implied by `-D warnings`
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#clone_on_copy
error: identical conversion
   --> src/call/mod.rs:158:30
    |
158 |         let in_len: size_t = size_t::from(buf.len());
    |                              ^^^^^^^^^^^^^^^^^^^^^^^ help: consider removing `size_t::from()`: `buf.len()`
    |
    = note: `-D clippy::identity-conversion` implied by `-D warnings`
    = help: for further information visit https://rust-lang-nursery.github.io/rust-clippy/v0.0.212/index.html#identity_conversion

Oh my god. I'll fix them

[ice1000]

Writing down some notes.

Also: rustfmt is complaining about the order of uses, should fix

Ref: https://travis-ci.org/pingcap/grpc-rs/jobs/439651311

[ice1000]

Edit: added some more TODOs

[ice1000]

Re-benched.

Qps:

Latency:

[ice1000]

Now this PR is up-to-date! I've added bytes support for MessageWriter!

For reviewers, you may only be interested in d5e7226 and f634dfa

[siddontang]

Thanks @ice1000

Have you already integrated it into TiKV and run the tests, benchmarks?

[ice1000]

Have you already integrated it into TiKV and run the tests, benchmarks?

Not yet in TiKV. Are you hurry? I have an essay due 5 days later while I've just get started (and I'm really really sorry about that 🙏) :(

[ice1000]

Travis CI GGed with this warning:

error: mutable borrow from immutable input(s)
   --> grpc-sys/src/lib.rs:415:62
    |
415 |     pub unsafe fn range_from_unsafe(&self, offset: usize) -> &mut [u8] {
    |                                                              ^^^^^^^^^
    |
    = note: `-D clippy::mut-from-ref` implied by `-D clippy::all`
note: immutable borrow here
   --> grpc-sys/src/lib.rs:415:37
    |
415 |     pub unsafe fn range_from_unsafe(&self, offset: usize) -> &mut [u8] {
    |                                     ^^^^^
    = help: for further information visit https://rust-lang.github.io/rust-clippy/master/index.html#mut_from_ref
error: aborting due to previous error

[Hoverbear]

Supersceded by #382 ?

[nrc]

Supersceded by #382 ?

Yes

[ice1000]

\o/