EIP-2200: Structured Definitions for Net Gas Metering

EIPS/eip-2200.md

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+---
+eip: 2200
+title: Rebalance net-metered SSTORE gas cost with consideration of SLOAD gas cost change
+author: Wei Tang (@sorpaas)
+discussions-to: https://github.com/sorpaas/EIPs/issues/1
+status: Draft
+type: Standards Track
+category: Core
+created: 2019-07-18
+requires: 1283, 1706, 1884
+---
+
+## Simple Summary
+
+A repricing effort for several trie-size-dependent opcodes are being
+carried out. This EIP also reprices net-metered SSTORE opcode.
+
+## Abstract
+
+Change the intermediate write and no-op write of SSTORE to always have
+the same gas cost of SLOAD. Change the refund of resetting after
+setting for SSTORE to take consideration of gas cost of SLOAD.
+
+## Motivation
+
+Net gas metering for SSTORE was priced according to SLOAD values. For
+consistency, when SLOAD is repriced, SSTORE should be as well.
+
+## Specification
+
+Define variables `SLOAD_GAS`, `SSTORE_SET_GAS`, `SSTORE_RESET_GAS` and
+`SSTORE_CLEARS_SCHEDULE`. The old and new values for those variables are:
+
+* `SLOAD_GAS`: changed from `200` to `800`.
+* `SSTORE_SET_GAS`: `20000`, not changed.
+* `SSTORE_RESET_GAS`: `5000`, not changed.
+* `SSTORE_CLEARS_SCHEDULE`: `15000`, not changed.
+
+Change the definition of EIP-1283 using those variables. The new
+specification, combining EIP-1283 and EIP-1706, will look like
+below. The terms *original value*, *current value* and *new value* are
+defined in EIP-1283. 
+
+Replace SSTORE opcode gas cost calculation (including refunds) with
+the following logic:
+
+* If *current value* equals *new value* (this is a no-op), `SLOAD_GAS`
+  is deducted.
+* If *current value* does not equal *new value*
+  * If *original value* equals *current value* (this storage slot has
+    not been changed by the current execution context)
+    * If *original value* is 0, `SSTORE_SET_GAS` is deducted.
+    * Otherwise, `SSTORE_RESET_GAS` gas is deducted. If *new value* is
+      0, add `SSTORE_CLEARS_SCHEDULE` gas to refund counter.
+  * If *original value* does not equal *current value* (this storage
+    slot is dirty), `SLOAD_GAS` gas is deducted. Apply both of the
+    following clauses.
+    * If *original value* is not 0
+      * If *current value* is 0 (also means that *new value* is not
+        0), remove `SSTORE_CLEARS_SCHEDULE` gas from refund
+        counter. We can prove that refund counter will never go below
+        0.
+      * If *new value* is 0 (also means that *current value* is not
+        0), add `SSTORE_CLEARS_SCHEDULE` gas to refund counter.
+    * If *original value* equals *new value* (this storage slot is
+      reset)
+      * If *original value* is 0, add `SSTORE_SET_GAS - SLOAD_GAS` to
+        refund counter.
+      * Otherwise, add `SSTORE_RESET_GAS - SLOAD_GAS` gas to refund
+        counter.
+* If *gasleft* is less than or equal to 2300, fail the current call
+  frame with 'out of gas' exception.
+
+An implementation should also note EIP-1283's refund counter
+implementation details, in the *Specification* section.
+
+## Rationale
+
+The same as EIP-1283's rationale. If EIP-1884 is applied, then `SLOAD_GAS`
+related to SSTORE opcode will also need to be changed.
+
+## Backwards Compatibility
+
+This EIP has the same backward compatibility property of EIP-1283 and EIP-1706.
+
+## Test Cases
+
+To be added.
+
+## Implementation
+
+To be added.
+
+## Copyright
+
+Copyright and related rights waived via [CC0](https://creativecommons.org/publicdomain/zero/1.0/).