Anza Block: Alessandro Decina

Solana validators are about to get dramatically faster. At Breakpoint 2025, Anza engineer Alessandro Decina unveiled a series of breakthrough performance improvements to the Agave validator client that could fundamentally change how the network operates—including turbine networking that's 200 times faster and validator restart times dropping from over 30 minutes to under 30 seconds.

Summary

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The presentation showcased months of intensive engineering work by the Anza team, delivering performance gains that touch nearly every critical component of Solana's validator infrastructure. Most notably, the implementation of XDP (eXpress Data Path) networking technology has achieved a staggering 200x speed improvement for turbine—the protocol responsible for distributing block data across the network. This breakthrough is already live in Agave 3.0 and represents the key technology that will enable Solana to increase its block space capacity.

Beyond networking, Decina detailed how the team has tackled long-standing bottlenecks throughout the codebase. A new serialization library called "Wingcode" has become the fastest Rust serialization library available, addressing chronic performance issues with the existing Bincode implementation. Epoch boundary crossing times have been slashed from over two seconds to under 400 milliseconds, and the scheduler—the component responsible for executing transactions when a validator is a leader—has been optimized from 61% overhead to just 9%.

Perhaps most impressively, validator restart times have undergone a dramatic transformation. What once took over 30 minutes in version 1.x now completes in under a minute in version 3.1, with version 4.x targeting sub-30-second restarts. This improvement alone represents a massive quality-of-life upgrade for validator operators who previously had to wait substantial amounts of time whenever they needed to restart their software.

Key Points

XDP Networking: The Foundation for Increased Block Space

XDP (eXpress Data Path) represents one of the most significant infrastructure upgrades in Solana's recent history. This technology allows network packets to be processed at the kernel level, bypassing much of the traditional networking stack overhead. Testing on both testnet and mainnet has demonstrated that turbine with XDP is 200 times faster than the legacy socket-based implementation.

What makes this achievement particularly notable is Anza's level of commitment to getting it right. The team has been working directly with Linux kernel maintainers, submitting patches to fix bugs discovered in both Intel and Broadcom network drivers. Decina highlighted that Anza is "literally the only team across all of blockchains sending patches to the Linux kernel"—a testament to the depth of their engineering approach.

The XDP implementation is being built as a standalone, reusable library that can benefit the broader ecosystem. Harsh from Tiny Dance has contributed the receive-side code, and Anza plans to integrate XDP into TPU (Transaction Processing Unit) in Q1 2025, which will allow the network to ingest transactions using this faster technology. The Overclock validator team has already leveraged this work to release Shredcaster, a low-latency alternative to Jito Shredstream for streaming shreds outside of turbine.

Wingcode: The Fastest Rust Serialization Library

Bincode, the serialization format used throughout Solana's protocol and on-chain applications, has been a persistent source of performance issues. While the wire format itself is reasonable, the implementation has caused bottlenecks that the team has had to fix "dozens of times" across different parts of the codebase.

Engineer Zach took on this challenge by creating Wingcode, a new serialization library built from scratch. The initial release immediately became the second-fastest Rust serialization library available. When the team expressed (jokingly) that second place wasn't good enough, Zach delivered a second release that claimed the top spot. Wingcode is now officially the fastest Rust serialization library, directly benefiting Solana's performance across the board.

Epoch Boundary Optimizations

Crossing epoch boundaries—the points where Solana's stake-weighted leader schedule rotates—has historically been a painful moment for the network. At the previous Accelerate conference, boundary crossings took more than two seconds and often caused validators to skip slots, reducing the network's effective throughput.

Through targeted optimizations by engineers Horan and Michal, epoch boundary crossing now completes in under 400 milliseconds. The team is "very close to not skipping slots anymore," with ongoing work expected to eliminate boundary-related slot skipping entirely.

Disk I/O Reduction: 93% Fewer Operations

A striking visualization showed the impact of disk I/O optimizations. In a 10-second profile of mainnet transaction replay, the previous implementation generated over 1,100 disk operations. The optimized code in master (and backported to 3.1) produces fewer than 80 operations in the same timeframe—a reduction of more than 93%.

This matters for two critical reasons: first, every disk operation introduces latency and jitter that affects both banking and replay performance; second, excessive writes wear out SSDs faster, directly impacting validators' hardware costs and maintenance schedules.

Validator Restart Times: From 30 Minutes to 30 Seconds

The evolution of restart times tells the story of sustained engineering focus on operator experience. Decina shared that when he first began performance optimization work nearly two years ago, restarting a validator took over 30 minutes—an absurdly long time that made iterative development painful. Version 2.x brought this under 10 minutes, version 3.1 achieves sub-minute restarts, and version 4.x targets under 30 seconds.

These improvements come purely from accounts database optimizations, without yet incorporating planned changes to replay and repair systems. Future versions will start even faster.

Scheduler Efficiency: From 61% Overhead to 9%

The scheduler determines how transactions are processed when a validator is producing blocks. A bug identified at the previous Accelerate conference showed that validators were spending 61% of their banking time on synchronization overhead rather than actually executing transactions.

Version 3.1 has completely resolved this issue. Workers now process transactions 91% of the time, with only 9% spent on coordination overhead. As Decina quipped about the remaining 10%: "you just need to send more transactions."

Facts + Figures

• Turbine with XDP is 200x faster than legacy socket-based turbine
• Anza is the only blockchain team submitting patches to the Linux kernel
• Wingcode is now the fastest Rust serialization library available
• Epoch boundary crossing time reduced from over 2 seconds to under 400 milliseconds
• Disk I/O operations reduced from over 1,100 to under 80 in a 10-second profile window
• Validator restart times: 1.x took 30+ minutes, 3.1 takes under 1 minute, 4.x will take under 30 seconds
• Scheduler efficiency improved from 39% useful work to 91% useful work
• XDP TPU integration planned for Q1 2025
• Decina has patches for both Intel and Broadcom Linux network drivers
• The AFXDP library is a standalone, reusable component for the broader ecosystem

Top Quotes

• "We are literally the only team across all of blockchains sending patches to the Linux kernel."

• "The second Wingcode release is the fastest Rust serialization library available."

• "We are very close to not skipping slots anymore. We still sometimes do skip one slot, but Michal is working on a fix so that we will never skip blocks again."

• "Why are you so obsessed with the restarts? Maybe just don't restart." (Previous response to restart complaints)

• "I love 3.0. It's the fastest release we've ever done. 3.1 is so much better, and I can't wait to release it."

• "The remaining 10%, you just need to send more transactions, OK?"

• "In these 10 seconds, there's less than 80 IO operations. So great work, IO people."

Questions Answered

What is XDP and why does it matter for Solana?

XDP (eXpress Data Path) is a high-performance networking technology that processes network packets at the Linux kernel level, bypassing much of the traditional networking stack. For Solana, implementing XDP in turbine—the protocol that distributes block data across validators—has resulted in 200x faster performance compared to legacy socket-based networking. This is critical because turbine's speed directly impacts how quickly the network can propagate blocks, and this improvement is what will enable Solana to increase its overall block space capacity.

How much faster will validator restarts be in upcoming Agave versions?

Validator restart times have improved dramatically across recent Agave versions. Version 1.x required over 30 minutes to restart, which was extremely painful for operators making configuration changes or updates. Version 2.x brought this under 10 minutes, version 3.1 achieves sub-minute restarts, and the upcoming version 4.x is targeting under 30 seconds. These improvements come from accounts database optimizations alone, with additional gains expected from planned replay and repair changes.

What was wrong with the previous scheduler and how was it fixed?

The previous scheduler had a bug that caused validators to spend 61% of their block production time on synchronization overhead with the Proof of History system rather than actually executing transactions. This meant only 39% of banking time was productive. Version 3.1 has completely fixed this issue, with workers now processing transactions 91% of the time. The remaining 9% represents necessary coordination overhead.

Why did Anza create Wingcode instead of continuing to use Bincode?

Bincode, while having a reasonable wire format, has an extremely slow implementation that has caused bottlenecks throughout the Solana codebase. The team had to fix Bincode-related performance issues "dozens of times" in different locations. Rather than continue patching around the problem, engineer Zach created Wingcode from scratch. It immediately became one of the fastest serialization libraries available, and after optimization, became the single fastest Rust serialization library.

What improvements were made to epoch boundary crossings?

Epoch boundaries are transition points where Solana's stake-weighted leader schedule rotates. Previously, crossing these boundaries took over two seconds and often caused validators to skip slots. Through optimizations by engineers Horan and Michal, boundary crossing now completes in under 400 milliseconds. The team is close to eliminating boundary-related slot skipping entirely, which will improve network throughput and reliability.

How does reduced disk I/O benefit validators?

The reduction in disk I/O operations—from over 1,100 to under 80 in a 10-second window—benefits validators in two ways. First, every disk operation introduces latency that adds jitter to both banking and replay operations, affecting performance. Second, excessive writes accelerate SSD wear, meaning validators have to replace expensive storage hardware more frequently. The 93% reduction in disk operations improves both performance and hardware longevity.

What ecosystem projects are already using Anza's XDP implementation?

The Overclock validator team has released Shredcaster, a project similar to Jito Shredstream that streams shreds outside of turbine. Because it uses Anza's XDP implementation, it has much lower overhead and sends with lower latency than alternatives. Additionally, Harsh from Tiny Dance has contributed the receive-side code to Anza's AFXDP library, which is designed as a standalone, reusable component for any project that needs high-performance networking.