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. NVIDIA GeForce GTX 970 Offers Great Linux Performance
  2. CompuLab Intense-PC2: An Excellent, Fanless, Mini PC Powered By Intel's i7 Haswell
  3. From The Atom 330 To Haswell ULT: Intel Linux Performance Benchmarks
  4. AMD Radeon R9 285 Tonga Performance On Linux
Latest Linux Articles
  1. AMD Moves Forward With Unified Linux Driver Strategy, New Kernel Driver
  2. MSI: Update Your BIOS From The Linux Desktop
  3. NVIDIA vs. AMD 2D Linux Drivers: Catalyst Is Getting Quite Good At 2D
  4. 15-Way GPU Comparison With Mesa 10.3 + Linux 3.17
Latest Linux News
  1. Features Of The Linux 3.18 Kernel
  2. Automatic Feedback Directed Optimizer Merged Into GCC
  3. Debian Now Defaults To Xfce On Non-x86 Desktops
  4. Phoenix Is Trying To Be An Open Version Of Apple's Swift
  5. Linux 3.19 To Have Skylake Graphics, PPGTT Enablement
  6. Ubuntu 16.04 Might Be The Distribution's Last 32-Bit Release
  7. Imagination Releases Full ISA Documentation For PowerVR Rogue GPUs
  8. Features GNOME Developers Want In The Linux Kernel
  9. GTK+ Gains Experimental Overlay Scrollbars
  10. Phoronix Test Suite 5.4 M3 Is Another Hearty Update
Latest Forum Discussions
  1. Users/Developers Threatening Fork Of Debian GNU/Linux
  2. Proof that strlcpy is un-needed
  3. xbox one tv tuner
  4. HOPE: The Ease Of Python With The Speed Of C++
  5. Bye bye BSD, Hello Linux: A Sys Admin's Story
  6. Updated and Optimized Ubuntu Free Graphics Drivers
  7. NVIDIA Presents Its Driver Plans To Support Mir/Wayland & KMS On Linux
  8. AMD Is Restructuring Again, Losing 7% Of Employees