Glossary OS

Plain meaning

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The dynamic memory region available to SBF programs during execution, defaulting to 32KB. Programs use heap memory for dynamic allocations (Vec, String, Box). The heap size can be increased up to 256KB by requesting additional compute units via the Compute Budget Program's RequestHeapFrame instruction. Heap exhaustion causes the program to fail with an AccessViolation error. Efficient programs minimize heap usage through zero-copy patterns and stack-allocated buffers.

Mental model

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Think of it as part of the chain machinery that keeps ordering, execution, or consensus moving.

Technical context

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Consensus, leader rotation, slots, epochs, and the runtime.

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Heap Memory (heap-memory)
Category: Core Protocol
Definition: The dynamic memory region available to SBF programs during execution, defaulting to 32KB. Programs use heap memory for dynamic allocations (Vec, String, Box). The heap size can be increased up to 256KB by requesting additional compute units via the Compute Budget Program's RequestHeapFrame instruction. Heap exhaustion causes the program to fail with an AccessViolation error. Efficient programs minimize heap usage through zero-copy patterns and stack-allocated buffers.
Related: Compute Budget, SBF (Solana Bytecode Format), Runtime

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Concept graph

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Branch

Compute Budget

The maximum compute units a transaction can consume. Default is 200,000 CU per instruction (max 1.4M CU per transaction). Programs can request specific limits via the ComputeBudgetProgram's SetComputeUnitLimit instruction. Under-requesting CU risks transaction failure; over-requesting wastes priority fee budget.

Compute Units (CU)Priority Fee

Open term

Branch

SBF (Solana Bytecode Format)

Solana Bytecode Format—Solana's customized evolution of BPF. SBF adds Solana-specific syscalls, modifies calling conventions, disables certain eBPF instructions, and adds features like position-independent code. Programs are compiled with `cargo build-sbf` and deployed as SBF ELF binaries. SBF replaced BPF as the canonical bytecode format.

BPF (Berkeley Packet Filter)Solana Virtual Machine (SVM)

Open term

Branch

Runtime

The component of the SVM responsible for loading programs, enforcing account access rules (ownership, writability, signer checks), managing compute budgets, and executing transactions. The runtime ensures programs can only modify accounts they own, charges rent, and enforces the 10MB per-transaction account data limit.

Sealevel Transaction

Open term

Next concepts to explore

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Programming Model

Compute Budget

The maximum compute units a transaction can consume. Default is 200,000 CU per instruction (max 1.4M CU per transaction). Programs can request specific limits via the ComputeBudgetProgram's SetComputeUnitLimit instruction. Under-requesting CU risks transaction failure; over-requesting wastes priority fee budget.

Open term

Core Protocol

SBF (Solana Bytecode Format)

Solana Bytecode Format—Solana's customized evolution of BPF. SBF adds Solana-specific syscalls, modifies calling conventions, disables certain eBPF instructions, and adds features like position-independent code. Programs are compiled with `cargo build-sbf` and deployed as SBF ELF binaries. SBF replaced BPF as the canonical bytecode format.

Open term

Core Protocol

Runtime

The component of the SVM responsible for loading programs, enforcing account access rules (ownership, writability, signer checks), managing compute budgets, and executing transactions. The runtime ensures programs can only modify accounts they own, charges rent, and enforces the 10MB per-transaction account data limit.

Open term

Core Protocol

Jito Validator Client

A modified fork of the Agave validator client maintained by Jito Labs that adds an out-of-protocol block space auction. Jito's modifications include a block engine that accepts transaction bundles with tips, enabling MEV extraction while returning value to stakers. The majority of mainnet-beta stake runs the Jito client.

Open term

Related terms

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Programming Modelcompute-budget

Compute Budget

The maximum compute units a transaction can consume. Default is 200,000 CU per instruction (max 1.4M CU per transaction). Programs can request specific limits via the ComputeBudgetProgram's SetComputeUnitLimit instruction. Under-requesting CU risks transaction failure; over-requesting wastes priority fee budget.

Open term

Core Protocolsbf

SBF (Solana Bytecode Format)

Solana Bytecode Format—Solana's customized evolution of BPF. SBF adds Solana-specific syscalls, modifies calling conventions, disables certain eBPF instructions, and adds features like position-independent code. Programs are compiled with `cargo build-sbf` and deployed as SBF ELF binaries. SBF replaced BPF as the canonical bytecode format.

Open term

Core Protocolruntime

Runtime

The component of the SVM responsible for loading programs, enforcing account access rules (ownership, writability, signer checks), managing compute budgets, and executing transactions. The runtime ensures programs can only modify accounts they own, charges rent, and enforces the 10MB per-transaction account data limit.

Open term

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Core Protocol

Proof of History (PoH)

A clock mechanism that cryptographically proves the passage of time between events. PoH uses a sequential SHA-256 hash chain where each output becomes the next input, creating a verifiable ordering of events without requiring consensus. The leader produces ~400,000 hashes per slot (~400ms), and any validator can verify the sequence in parallel, enabling Solana's high throughput by removing the need for validators to agree on time.

Open term

Core Protocol

Tower BFT

Solana's custom BFT consensus algorithm built on top of Proof of History. Tower BFT uses PoH as a clock to reduce communication overhead in traditional PBFT from O(n²) to O(n). Validators vote on forks with exponentially increasing lockout periods—each consecutive vote doubles the lockout, making rollbacks progressively more expensive. A fork is finalized when it reaches supermajority (66.7%+ of stake).

Open term

Core Protocol

Slot

A time window during which a designated leader validator can produce a block. Each slot lasts approximately 400 milliseconds. Slots are numbered sequentially from genesis and grouped into epochs of 432,000 slots (~2-3 days). Not every slot produces a block—a skipped slot means the leader was offline or too slow.

Open term

Core Protocol

Block

A set of entries produced by a leader during a single slot. A block contains transactions bundled into entries, each with a PoH hash proving ordering. Blocks are broken into shreds for network propagation via Turbine. Maximum block size is limited by compute units (48M CU cap per block) rather than byte size.

Open term