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Minimize linkage during VM instantiation #1292

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graydon opened this issue Dec 5, 2023 · 1 comment
Closed

Minimize linkage during VM instantiation #1292

graydon opened this issue Dec 5, 2023 · 1 comment
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enhancement New feature or request

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graydon commented Dec 5, 2023

VM instantiation spends a third of its time defining host functions in the linker -- these are fairly atomics-heavy operations due to threadsafety in wasmi -- and this can be minimized if we filter for the host functions that a contract actually uses.

The caveat here is that in the worst case a contract could still use all host functions, so from a metering perspective we would probably have to make the instantiation costs more granular (eg. introduce a new cost type LinkVMFunction with a linear model based on the number used, or something).
@graydon graydon added the enhancement New feature or request label Dec 5, 2023
@graydon graydon mentioned this issue Feb 29, 2024
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github-merge-queue bot pushed a commit that referenced this issue Mar 26, 2024
@graydon
Decompose VM instantiation costs and add module cache (#1359)
41b4ee3 
This is a sketch of the first step in the plan for addressing #1292 and
eventually #827 and #1313, namely:

- add a bunch of cost types that decompose the current "worst case" VM
instantiation cost type
  - continue to charge the worst case on initial contract upload
- _store_ the decomposed cost-type inputs in the ledger, since we can
observe them after the initial upload parse
- _use_ those decomposed cost-type inputs when doing runtime
instantiation
  - add a module cache
  - populate the module cache with all modules on host startup
  - use cached modules during instantiation

This PR has accompanying changes in XDR and wasmi:

  - stellar/stellar-xdr#177
  - stellar/rs-stellar-xdr#346

Remaining to do:

  - [x] determine what the correct set of decomposed cost types even is
  - [ ] ~add more code to wasmi to enable observing more inputs~
- [x] add cost-type runners / calibrations for all the decomposed
cost-types
  - [x] protocol-gate this new behaviour
- [x] make the linker-loop do less work to match the tighter cost model
(i.e. complete #1292)
- [x] possibly _duplicate_ the set of cost types added here, so we have
a cached and uncached version of each, and implement a solution to #827
- [ ] possibly decompose the set sufficiently to model what will happen
when we take wasmi 0.32 and enable lazy translation (i.e. complete
#1313)
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graydon commented Apr 8, 2024

Fixed by #1359 and #1375

@graydon graydon closed this as completed Apr 8, 2024
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