Optimize `interpreter::blockchain::{load_contract_code, code_copy` to read contract starting from offset #847

acerone85 · 2024-10-04T16:06:52Z

[Link to related issue(s) here, if any]

Closes #681

[Short description of the changes.]

When loading the contract code into the stack, we use the new semantics of StorageRead from #863 to only fetch the portion of a contract starting from the specified offset. We also read the contract bytes directly into the stack.

A similar optimization is done for code_copy.

Checklist

Breaking changes are clearly marked as such in the PR description and changelog
New behavior is reflected in tests
If performance characteristic of an instruction change, update gas costs as well or make a follow-up PR for that
The specification matches the implemented behavior (link update PR if changes are needed)

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I have reviewed the code myself
I have created follow-up issues caused by this PR and linked them here

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Rust SDK
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Someone else?

netrome

Looks alright to me. The TODO comment needs to be resolved before I can approve. There's also some code duplication that I think we could factor out, but that's not blocking from my end.

fuel-vm/src/interpreter/blockchain.rs

netrome

Nice stuff!

netrome · 2024-10-22T12:46:36Z

Poke me when you've fixed the clippy errors and I'll re-approve

MitchTurner

I'm not a VM guy, so maybe I could get you to walk me through these changes.

MitchTurner · 2024-10-22T16:28:05Z

CHANGELOG.md

@@ -7,6 +7,9 @@ and this project adheres to [Semantic Versioning](http://semver.org/).

 ## [Unreleased]

+### Changed 
+- [#847](https://github.com/FuelLabs/fuel-vm/pull/847): Remove `contract_read`, and change `load_contract_code`, `code_copy` and `code_root`  to explicitly load the contract code in a buffer. Also check for mismatches between contract size stored and actual size of contract in those functions.


I'm confused by this. There is no function called contract_read that is removed in these changes. And you added a call to read_contract, which sounds like the same thing?

MitchTurner · 2024-10-22T16:29:07Z

fuel-vm/src/interpreter/blockchain.rs

+        .ok_or(PanicReason::ContractNotFound)?
+        .map_err(RuntimeError::Storage)?;
+
+    if contract_buffer.len() != contract_len {


If it's already allocated to to contracct_len size, will the len call ever not be contract_len?

Yes, this is a leftover from refactoring, most probably this check should not be there.
(Btw, I noticed that we have a slightly different implementation of the same function:

fuel-vm/fuel-vm/src/interpreter/flow.rs

Line 631 in a6abe47

fn read_contract<S>(

, so maybe we should factor out the common code and have only one function instead)

xgreenx · 2024-10-22T17:13:20Z

fuel-vm/src/interpreter/blockchain.rs

-        let contract = super::contract::contract(self.storage, &contract_id)?;
-        let contract_bytes = contract.as_ref().as_ref();
+
+        let contract_buffer: Vec<u8> = load_contract_code_from_storage(


After reviewing this change, I see that we basically have the same code as before and allocate vectors in all cases.

So basically, this change doesn't make a lot of sense=D

The main problem is why we can't do the optimal implementation and copy directly into the memory - contract offset(and blob offset, since we have the same problem for blobs LDC with mode == 1 and BLDD opcode).

I think we need to extend the StorageRead trait if we want to fix this issue in a proper way. A new method will do the same as the read or change the read method itself to something like:

fn read(&self, key: &Type::Key, offset: usize, buf: &mut [u8]) -> Result<Option<usize>, Self::Error>

Could you change this method to work with offset and update all code to not allocate vector, please?

Also, it would be nice if you do the same for blobs as well.

Yes, the original idea was to have only one allocation. The only actual improvement in this PR as is now is fixing <MemoryStorage as StorageRead>::read`, which was panicking before due to slices of been different size being copied.

Happy to extend the trait to read. I think it would be better to add a new function read_from_offset, and then change read to be a provided method with offset 0

I'm fine with the new method and with reworking the old one. I think changing the old one makes more sense because the compiler will help you identify places that also need to be updated in the code to avoid allocation of the Vec. Plus this read function only exists for load opcodes, so they mainly define their existence, usage and shape.

Sure, just to make sure: if we opt for modifying the StorageRead::read function, then there will be several places where the implementation needs to be updated, both in fuel-vm and fuel-core; also it is not clear to me that we can read from an arbitrary offset easily in all the implementations of the StorageRead trait. But I will try and see how far can I go before getting into trouble

acerone85 · 2024-10-23T09:45:39Z

I'm not a VM guy, so maybe I could get you to walk me through these changes.

Happy to do it once I address the comments left by @xgreenx :)

…pecified offset

acerone85 · 2024-11-12T15:20:32Z

fuel-vm/src/interpreter/blockchain.rs

-        let contract_bytes = contract.as_ref().as_ref();
-        let contract_len = contract_bytes.len();
+        let contract_bytes = self.memory.write(self.owner, dst_addr, length)?;
+        let contract_len = contract_size(&self.storage, &contract_id)?;
        let charge_len = core::cmp::max(contract_len as u64, length);


We never read more than length bytes with the new version. Should charge_len be changed accordingly to reflect this?

acerone85 · 2024-11-12T15:23:20Z

With the new version the function code_root still uses the old StorageInspect::get<RawContractCode> function. This seems to be okay to me, as the function will return a borrowed reference to the whole contract, which will then be moved into chunks into a MerkleTree structure to compute the code root. In this case, using StorageRead::read<RawContractCode> would require allocating more space to store the contract code, which can be avoided. Do you agree with this?

acerone85 requested review from xgreenx, Dentosal and MitchTurner as code owners October 4, 2024 16:06

acerone85 marked this pull request as draft October 4, 2024 16:06

acerone85 force-pushed the 681_remove_storage_read branch from 318b0b3 to 9f4117d Compare October 4, 2024 16:20

Copy directly into stack when loading contract code

ab0cc7b

acerone85 force-pushed the 681_remove_storage_read branch from 9f4117d to ab0cc7b Compare October 4, 2024 16:30

acerone85 added 5 commits October 4, 2024 19:05

Update gas costs

816390f

Merge branch 'master' into 681_remove_storage_read

994008e

Update changelog

ded2cff

Merge branch 'master' into 681_remove_storage_read

ccfbb61

Revert optimization on LDC

ef32062

acerone85 self-assigned this Oct 14, 2024

acerone85 marked this pull request as ready for review October 14, 2024 12:47

acerone85 requested a review from Voxelot as a code owner October 14, 2024 12:47

Merge branch 'master' into 681_remove_storage_read

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netrome reviewed Oct 22, 2024

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fuel-vm/src/interpreter/blockchain.rs Outdated Show resolved Hide resolved

acerone85 added 3 commits October 22, 2024 13:19

Merge branch 'master' into 681_remove_storage_read

83a97ba

Remove TODO comment

8c6ced6

Isolate load contract code to helper function

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netrome previously approved these changes Oct 22, 2024

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Address clippy's errors

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acerone85 dismissed netrome’s stale review via 010dd6f October 22, 2024 13:59

netrome previously approved these changes Oct 22, 2024

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MitchTurner reviewed Oct 22, 2024

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xgreenx reviewed Oct 22, 2024

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WIP: Change Storage Read trait

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xgreenx mentioned this pull request Oct 30, 2024

Add the possibility to specify an offset for the read value in StorageRead::read #863

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Merge branch 'master' into 681_remove_storage_read

470cd31

acerone85 dismissed netrome’s stale review via 470cd31 November 12, 2024 13:13

acerone85 added 3 commits November 12, 2024 15:04

Reset to master

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Optimize load_contract and code_copy to read contract starting from s…

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…pecified offset

Changelog

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acerone85 commented Nov 12, 2024

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acerone85 changed the title ~~Remove storage read~~ Optimize interpreter::blockchain::{load_contract_code, code_copy to read contract starting from offset Nov 13, 2024

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Optimize `interpreter::blockchain::{load_contract_code, code_copy` to read contract starting from offset #847

Optimize `interpreter::blockchain::{load_contract_code, code_copy` to read contract starting from offset #847

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acerone85 commented Oct 23, 2024 •

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acerone85 commented Nov 12, 2024

Optimize interpreter::blockchain::{load_contract_code, code_copy to read contract starting from offset #847

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Optimize interpreter::blockchain::{load_contract_code, code_copy to read contract starting from offset #847

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acerone85 commented Oct 4, 2024 • edited Loading

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acerone85 commented Oct 23, 2024 • edited Loading

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acerone85 commented Nov 12, 2024

Optimize `interpreter::blockchain::{load_contract_code, code_copy` to read contract starting from offset #847

Optimize `interpreter::blockchain::{load_contract_code, code_copy` to read contract starting from offset #847

acerone85 commented Oct 4, 2024 •

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acerone85 commented Oct 23, 2024 •

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