Linux 6.4-rc6 Released: What’s New?

The Linux 6.4-rc6 kernel was released on June 12, 2023. The Linux 6.4 kernel, slated for release on June 25, 2023, is now in its sixth and last release candidate. A number of new functions and bug fixes are present in the Linux 6.4 kernel.

Among the highlights are:

  • The new ZRAM compressed memory allocator is supported.
  • The new CXL 2.0 connector standard is supported.
  • enhanced compatibility with AMD’s Zen 4 processor architecture
  • many bug fixes for different hardware platforms

A important update to the Linux operating system, the Linux 6.4 kernel adds a number of new features and enhancements. It is recommended that Linux users update to the Linux 6.4 kernel when it becomes available.

ZRAM compressed memory allocator

A new feature in Linux 6.4-rc6 called the ZRAM compressed memory allocator can be used to increase performance and memory use on Linux systems with low memory. ZRAM functions by keeping compressed versions of unused memory pages in memory. These pages are compressed and used normally when the system needs to access them.

ZRAM has the potential to significantly boost the performance of systems with little available memory. It sometimes enhances performance by as much as 50%. ZRAM can also increase system stability by ensuring that there is never a memory shortage.

The following line must be added to your /etc/default/grub file to enable ZRAM.


This will allocate 16MB of memory for ZRAM. You can also use the zramctl command to manually control ZRAM.

The following are some advantages of utilizing ZRAM:

  • Performance gain: ZRAM can boost the performance of memory-constrained systems by compressing wasted memory pages. Particularly for systems with lots of small, frequently visited memory pages, this can result in a large speed improvement.
  • Increased memory efficiency: ZRAM can increase memory efficiency by compressing unneeded memory pages. This could free up RAM for other programs, improving the user experience in general.
  • Increased system stability: ZRAM can aid in enhancing system stability by preventing memory outages. By doing this, system failures and other issues may be avoided.

Consider turning on ZRAM if you are operating a system with little available memory. It may be a quick and easy approach to increase your system’s performance, memory use, and reliability.

CXL 2.0 interconnect support

The CXL 2.0 interconnect standard is a new high-speed interconnect that can be used to connect different components of a computer system. The connection specification for PCI Express will be replaced by CXL 2.0.

Support for the CXL 2.0 connection standard has been included in Linux 6.4-rc6. As a result, Linux systems can now link various parts, including CPUs, GPUs, and storage devices, using CXL 2.0.

Compared to PCI Express, CXL 2.0 has a number of benefits, including:

  • Greater bandwidth: CXL 2.0 is capable of providing up to 128 GB/s of bandwidth per lane, as opposed to PCI Express 4.0’s 16 GB/s.
  • Less latency: CXL 2.0 has less latency than PCI Express, which might enhance the performance of programs that depend on latency.
  • More adaptability: Compared to PCI Express, CXL 2.0 is more adaptable and supports a wider range of use cases.

The addition of CXL 2.0 functionality in Linux 6.4-rc6 is a significant advancement for the Linux operating system. It will enable Linux systems to take use of the CXL 2.0 interconnect standard’s speed and versatility.

Here are a few of CXL 2.0’s standout characteristics:

  • Memory-attached I/O (MAI): By enabling direct memory attachment of devices, MAI can enhance performance and lower latency.
  • Remote direct memory access (RDMA) enables direct memory access to external devices, which can enhance performance and scalability.
  • Data corruption can be avoided because to CXL 2.0’s coherency between memory that is accessed by various devices.

CXL 2.0 is a new standard, and it is still in the early stages of adoption. However, it has the potential to revolutionize the way that computer systems are designed and built. Linux 6.4-rc6 is one of the first operating systems to support CXL 2.0, and this support will help to accelerate the adoption of this new standard.

AMD Zen 4 processors

If you are using a Linux system with an AMD Zen 4 processor, you can upgrade to the Linux 6.4-rc6 kernel to take advantage of these performance and power efficiency improvements.

Here are some of the key features of AMD Zen 4:

  • New Zen 4 instruction set: The Zen 4 instruction set includes a number of new instructions that can be used to improve performance. These new instructions include instructions for vectorized operations, cryptography, and machine learning.
  • New Zen 4 memory controller: The Zen 4 memory controller is designed to improve memory bandwidth and latency. It also supports new memory technologies, such as DDR5 memory.
  • New Zen 4 power management features: The Zen 4 power management features are designed to improve power efficiency. These features include a new power gating system and a new thermal management system.

AMD Zen 4 is a significant improvement over AMD Zen 3. It offers significant performance improvements, as well as improved power efficiency. If you are using a Linux system with an AMD Zen 4 processor, you can upgrade to the Linux 6.4-rc6 kernel to take advantage of these performance and power efficiency improvements.

Bug fixes

Here are a few of the issues that Linux 6.4-rc6 fixes:

  • The XFS filesystem has been updated to address an issue that might have led to a system crash.
  • A CXL 2.0 driver flaw that might have led to a system hang has been repaired.
  • The AMD Zen 4 processor driver has a problem that might have led to a system crash, but it has been addressed.
  • Linux’s performance and stability have been enhanced by a number of additional bug fixes.

You can upgrade to Linux 6.4-rc6 if you’re running a Linux system by following the directions in the documentation for your distribution.

Here are some additional details about the bug fixes:

  • A race problem in the code that controls the filesystem’s journal led to the XFS filesystem bug. A concurrent write operation could set off the flaw, which could result in a system crash.
  • The device discovery code contained a logical flaw that led to the CXL 2.0 driver problem. A device that was improperly setup may have caused the bug, which could result in the system hanging.
  • A race condition in the code that controls the chip’s power management functions led to the AMD Zen 4 processor driver problem. The flaw could result in a system crash and be brought on by concurrent access to the processor’s power management registers.

The other bug fixes that have been made to improve the stability and performance of Linux include fixes for:

  • A bug in the network driver could cause the system to lose network connectivity.
  • A bug in the graphics driver could cause the system to crash when running certain applications.
  • A bug in the filesystem driver could cause the system to lose data when writing to a filesystem.

These are just a few of the bug fixes that have been made in Linux 6.4-rc6. For a complete list of bug fixes, please refer to the release notes.

Wrapping Up

Significant improvements and intriguing new features were introduced to the Linux community with the Linux Kernel 5.7. With its release, users and developers have access to a number of enhancements that improved functionality, performance, and security. Key additions like updated drivers, enhanced filesystem capabilities, and support for new hardware demonstrated how the Linux ecosystem is always evolving. It is recommended that Linux users update to the Linux 6.4-rc6 kernel when it becomes available.

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