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. AMD R600g/RadeonSI Performance On Linux 3.16 With Mesa 10.3-devel
  2. Intel Pentium G3258 On Linux
  3. SilverStone Precision PS10
  4. ASRock Z97 Extreme6
Latest Linux Articles
  1. Nouveau vs. Radeon vs. Intel Tests On Linux 3.16, Mesa 10.3-devel
  2. KVM Benchmarks On Ubuntu 14.10
  3. X.Org Server 1.16 Officially Released With Terrific Features
  4. Ubuntu With Linux 3.16 Smashes OS X 10.9.4 On The MacBook Air
Latest Linux News
  1. A New Video Has Us Real Excited About The New UT For Linux
  2. CoreOS Experiences Its First Stable Release
  3. GNOME 3.13.4 Continues Working On Wayland & More
  4. Wine 1.7.23 Has Initial Support For 64-bit Android Builds
  5. FreeBSD Developing A New Automounter, Other Features
  6. Guix 0.7 Can Now Install The GNU Operating System
  7. X.Org Foundation Still Works Towards Becoming An SPI Project
  8. Open-Source AMD Hawaii Support Should Now Be Working!
  9. KDE Developers Continue Working Toward Wayland Support
  10. Ubuntu 14.04.1 LTS Released
Latest Forum Discussions
  1. Updated and Optimized Ubuntu Free Graphics Drivers
  2. AMD "Hawaii" Open-Source GPU Acceleration Still Not Working Right
  3. Radeon related kernel bug??
  4. how the US intellegentia operates:
  5. AMD Publishes Open-Source Linux HSA Kernel Driver
  6. Next-Gen OpenGL To Be Announced Next Month
  7. Open-Source Radeon Performance Boosted By Linux 3.16
  8. Remote gui not accessible in Phoronix Test Suite 5.2