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 Articles & Reviews
  1. AMD FX-8320E Performance On Linux
  2. Linux Compiler Benchmarks Of LLVM Clang 3.5 vs. LLVM Clang 3.6-rc1
  3. Intel Broadwell HD Graphics 5500: Windows 8.1 vs. Linux
  4. Linux Benchmarks Of NVIDIA's Early 2015 GeForce Line-Up
  5. NVIDIA GeForce GTX 960: A Great $200 GPU For Linux Gamers
  6. Disk Encryption Tests On Fedora 21
Latest Linux News
  1. Now-Closed KDE Vulnerabilities Remind Us X11 Screen Locks / Screensavers Are Insecure
  2. Vivaldi: A New Chromium-Powered, Multi-Platform Browser
  3. KDE Plasma 5.2 Officially Released
  4. Intel Broadwell On Linux Has Working OpenCL 1.2, VP8 Video Acceleration
  5. GParted 0.21 Brings ReFS Detection, EXT4 For RHEL5, Reiser4 For Linux 3.x
  6. Wine Staging Update Has Better CUDA Support, Driver Testing Framework
  7. Nouveau In Linux 3.20 Will Have A Lot Of Code Cleaning
  8. Compare Your Linux System To The i7-5600U Broadwell X1 Carbon ThinkPad
  9. Debian 8.0 "Jessie" Installer RC1 Released
  10. Chromebook "Rush" With 64-bit Tegra SoC Support Lands In Coreboot
Most Viewed News This Week
  1. Windows 10 To Be A Free Upgrade: What Linux Users Need To Know
  2. Google Admin Encourages Trying Btrfs, Not ZFS On Linux
  3. TraceFS: The Newest Linux File-System
  4. My Initial Intel Broadwell Linux Experience With The ThinkPad X1 Carbon
  5. Keith Packard Leaves Intel's Linux Graphics Work
  6. Interstellar Marines On Linux With Catalyst: Bull S*#@
  7. Faster VP9 Decoding Is On The Horizon
  8. NetworkManager Now Supports WiFi Power Savings