Linux Kernel Patch Series Promises Massive Hibernation Speedups for Slow SSDs

A Linux kernel developer has submitted a patch series that could dramatically improve hibernation performance, particularly for systems using older or slower solid-state drives. The optimization focuses on the kernel's swap file code and promises to reduce hibernation times from several minutes to under a minute in some cases.

The Problem with Slow SSDs and Hibernation

When a system hibernates, the kernel must write the entire contents of RAM to disk. For systems with slower storage devices, especially older SSDs with poor 4K write performance, this process can take an extraordinarily long time. The current Linux kernel's swap allocator wasn't optimized for this specific use case, leading to suboptimal performance during hibernation operations.

The Solution: A New Fast Allocation Path

Kairui Song's patch series introduces a new fast allocation path in the swap allocator that's specifically designed to handle hibernation more efficiently. The change involves reworking just over two dozen lines of code, but the performance impact is substantial.

Dramatic Performance Improvements

The most striking example comes from testing with a Samsung 830 SSD, which uses the older Serial ATA 2.0 interface. With Linux 6.19 kernel, hibernating this system took a staggering 324 seconds (5 minutes and 24 seconds). After applying the new patches, that time drops to just 35 seconds - a nearly 10x improvement.

While the performance gains are most dramatic on slower storage devices, even faster SSDs see some benefit. The patches are particularly effective for drives with poor 4K write performance, where the speed improvements can be "several times better" according to the developer.

Technical Details

The optimization works by creating a more efficient allocation strategy for the hibernation process. The swap allocator now has a dedicated fast path that better handles the sequential write patterns typical of hibernation, rather than treating it like a general-purpose memory swap operation.

Timeline and Availability

The patches are currently under review and were submitted too late to be included in the Linux 7.0 kernel cycle. However, they could potentially be merged for the v7.1 kernel release, which is expected mid-year.

Impact for Users

This improvement is particularly relevant for:

• Users with older laptops that use SATA 2.0 SSDs
• Systems with budget SSDs that have poor random write performance
• Anyone who frequently uses hibernation instead of shutdown
• Enterprise environments where hibernation speed affects productivity

For most modern NVMe drives, the performance impact will be minimal since they already have excellent 4K write performance. However, for the millions of systems still running older SATA SSDs, this patch series could significantly improve the hibernation experience.

Testing Methodology

The performance claims are based on benchmarks comparing hibernation times before and after the patches on various storage devices. The Samsung 830 SSD test provides the most dramatic before-and-after comparison, going from 324 seconds to 35 seconds - a reduction of nearly 90% in hibernation time.

Future Considerations

As storage technology continues to evolve, with faster interfaces and improved NAND flash controllers, the absolute impact of these optimizations may diminish over time. However, the principle of optimizing kernel behavior for specific use cases remains valuable, and similar approaches could be applied to other performance bottlenecks in the Linux kernel.

For now, users with older systems or budget SSDs have reason to be excited about the potential for dramatically faster hibernation times in upcoming kernel releases.