1. Computers
  2. Display Drivers
  3. Graphics Cards
  4. Memory
  5. Motherboards
  6. Processors
  7. Software
  8. Storage
  9. Operating Systems


Facebook RSS Twitter Twitter Google Plus


Phoronix Test Suite

OpenBenchmarking.org

Zswap: Compressed Swap Caching For Linux

Linux Kernel

Published on 12 December 2012 09:20 PM EST
Written by Michael Larabel in Linux Kernel
16 Comments

Published to the Linux kernel mailing list were a set of patches to provide a new feature called Zswap for lightweight compressed swap caching.

These patches, while arriving unfortunately right at the start of the Linux 3.8 kernel merge window and have yet to be reviewed, provide Zswap (not to be confused by zRAM) to attempt to compress pages in the process of being swapped and compresses them into a dynamically allocated RAM-backed memory pool. Zswap attempts to avoid the writeback to the swap device where possible to reduce I/O and lead to greater performance in situations where swapping occurs.

Seth Jennings, the developer who published the set of eight patches, summarized the performance benefits as "a kernel building benchmark indicate a runtime reduction of 53% and an I/O reduction 76% with zswap vs normal swapping with a kernel build under heavy memory pressure."

The expressed rationale was said to be, "Zswap provides compressed swap caching that basically trades CPU cycles for reduced swap I/O. This trade-off can result in a significant performance improvement as reads to/writes from to the compressed cache almost always faster that reading from a swap device which incurs the latency of an asynchronous block I/O read."

Among the use-cases are desktops/laptops with limited RAM where there can be better performance when swapping, overcommitted guests that share a common I/O resource, and users of SSDs as swap devices whereby they can potentially extend the solid state drive's life by reducing the number of writes.

For more information on Zswap, see the kernel mailing list, where there are also some more extensive Zswap performance benchmark results. Based upon early feedback on the Zswap patches, it will probably still be a while before this compression feature is merged into the mainline Linux kernel.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
Latest Linux Hardware Reviews
  1. A Walkthrough Of The New 32 System Open-Source Linux Benchmarking Test Farm
  2. Habey MITX-6771: Mini-ITX Board With Quad-Core J1900 Bay Trail
  3. OCZ Vector 150 SSD On Linux
  4. Noctua i4 CPU Cooler: Great For Cooling High-End LGA-2011v3 CPUs
Latest Linux Articles
  1. AMD Kaveri: Open-Source Radeon Gallium3D vs. Catalyst 14.12 Omega Driver
  2. 12-Way AMD Catalyst 14.12 vs. NVIDIA 346 Series Linux GPU Comparison
  3. AMD Catalyst 14.12 Omega Driver Brings Mixed Results For Linux Users
  4. 6-Way Winter 2014 Linux Distribution Comparison
Latest Linux News
  1. Linux 3.19-rc1 Kernel Released Ahead Of Schedule
  2. Civilization: Beyond Earth Linux GPU/Driver Benchmarks
  3. X.Org Server 1.16.3 Released To Fix Security Issues
  4. Linux 3.19 Merge Window Closes Ahead Of Schedule
  5. MIPS R6 Architecture Now Supported By GCC
  6. LowRISC To Feature Tagged Memory & Minion Cores
  7. Intel Skylake Audio Support For Linux 3.19
  8. After 10+ Years, NetworkManager Reaches v1.0
  9. VDPAU Updated To v0.9
  10. An Open Hardware Random Number Generator Proposed
Latest Forum Discussions
  1. FPS capped on Linux (AMD fglrx drivers)
  2. Need some hand holding with upgrading xserver
  3. Are there an app using HSA ?
  4. The New SuperTuxKart Looks Better, But Can Cause GPU/Driver Problems
  5. XLennart: A Game For Systemd Haters With Nothing Better To Do
  6. Updated and Optimized Ubuntu Free Graphics Drivers
  7. Debian init discussion in Phoenix Wright format
  8. Bench specific mount point