http://code.google.com/p/compcache/
This project creates RAM based block device (named ramzswap)
which acts as swap disk. Pages swapped to this disk are compressed and
stored in memory itself.
Compressing
pages and keeping them in RAM virtually increases its capacity. This
allows more applications to fit in given amount of memory.
The usual argument I get is - memory is so cheap so why
bother with compression? So I list here some of the use cases.
Rest depends on your imagination :)
- Netbooks:
Market is now getting flooded with these "lighweight laptops". These
are memory constrained but have CPU enough to drive on compressed
memory (e.g. Cloudbook features 1.2 GHz processor!).
- Virtualization: With compcache at hypervisor
level, we can compress any part of guest memory
transparently - this is true for any type of Guest OS (Linux,
Windows etc.). This should allow running more number of VMs for given
amount of total host memory.
- Embedded Devices:
Memory is scarce and adding more memory increases device cost. Also,
flash storage suffers from wear-leveling issues, so its useful if we
can avoid using them as swap device.
linux-mm-cc at laptop dot org (Info
Page)
ngupta at vflare dot org (vflare.org)
- Aug 20, 09 - compcache-0.6 is released.
- Aug 09, 09 - multiple_rzs and default branch
merged.
- Aug 06, 09 - compcache-0.6-pre3 released. It
includes experimental support for swap free notify feature
which eliminates any stale data from ramzswap -- README and CompilingAndUsingNew
has details on how to enable this feature. It also includes fix for
invalid stats reporting on ARM ( Issue
#34 ). See Changelog for details.
- Jul 20, 09 - compcache-0.6-pre2 is out. It includes fix for
crashes on ARM (see Issue
#33 ). See Changelog included for full list for changes.
- Jul 14, 09 - compcache-0.6-pre1 released! New features include
creating multiple ramzswap devices, ability to have file as a
backing swap. See CompilingAndUsingNew
for help. This required major code changes, so it needs good amount of
testing before any serious use.
- May 28, 09 - Project switches to mercurial.
- May 26, 09 - compcache article featured at LWN.net.
- Apr 08, 09 - compcache 0.5.3 released. This includes major
cleanups. LZO modules are no longer included in package since most
distros now already include these. There is change in name for module
and parameters - README and CompilingAndUsing
page are updated to reflect these changes.
- Apr 03, 09 - It could not make it into 2.6.30 due to lack of
supporting data. See this post on LKML. Now the point is, what data to
collect? Can we get it by next kernel release??
- Mar 29, 09 - Effort to push it to mainline has started.
I have uploaded the kernel patch in Downloads section. Please test it
with whatever benchmarks you can think of and let me know any
problems you get. Your support can help make it into mainline. Please
note that there is change in module name (compcache -> ramzswap) and
change in names of configuration parameters. So, please go through
Documentation/blockdev/ramzswap.txt. The patch applies against 2.6.29
(during menuconfig, select Device Drivers -> Block Devices ->
Compressed RAM swap device). Thanks!
- Mar 11, 09 - compcache
0.5.2 released! Most notable features include ability to send
incompressible pages to physical swap and no memory allocation for
zero-filled pages. See Changelog included for all details. There are
also changes to module parameters so check updated CompilingAndUsing
page before using.
- Feb
24, 09 - Now we can forward incompressible pages to physical swap disk!
Support is still experimental but I hope to get it stable by next
release :)
- Feb 23, 09 - TipsAndTricks wiki created!
- Jan 22, 09 - compcache-0.5.1 released. This fixes crash that
could happen only on x86 with highmem (mem > ~1G). See Issue
#20 for details.
- Jan
15, 09 - compcache-0.5 is out! This completes transition to new
xvMalloc memory allocator. There is one additional bugfix in this final
release.
- Jan 10, 09 - compcache-0.5pre4 released. Finally
this includes ability to free memory associated with freed swap blocks
(similar to what compcache patch does but less aggressive). This
feature requires 2.6.29-rc1 - if compiled on older kernel, this
functionality will not be available. It also fixes incorrect stats
reporting in /proc/compcache. See Changelog included for more details.
- Jan 05, 09 - compcache-0.5pre3 released. Fixes system freeze issue
#19 (tested on x86 and x64).
- Dec 28, 08 - compcache-0.5pre2 released - see Changelog included
for details. Happy New Year!
- Dec 15, 08 - compcache-0.5pre1 released! This is preview release
integrates xvMalloc memory allocator replacing TLSF.
- Oct
03, 08 - xvMalloc: New memory allocator. This removes dependence on
kernel vmalloc area. Its also quite memory efficient! Details here.
- Aug 13, 08 - compcache-0.4 now available. Nothing new but few
bug fixes and lot of cleanups. See Changelog included for details.
- Jul
18, 08 - After lot more rigorous testing (on x86), compcache patches
are now available from Downloads area. For help on using these patches,
refer Patches. Out-of-tree kernel modules are still
available.
- Jul 14, 08 - Patch for 2.6.26 is (here) and here is Changelog.
- Jun 29, 08 - Here comes patch for Linux kernel 2.6.26-rc8 (download).
It fixes bug in previous patch that could cause segfault when loading
module and free invalid memory in swap free notify callback.
- Jun 17, 08 - Patch for Linux kernel 2.6.26-rc6 for compcache is here - Its better than compcache-0.3 in terms of
space efficiency, speed and also has lot of cleanups.
- May 13, 08 - Some Performance numbers.
- Apr 28, 08 - Todo list is here
- Mar 17, 08 - compcache-0.3 Released with more bug fixes!
- Mar 03, 08 - compcache-0.2 Released! Now it also exports
statistics through /proc.
- Feb 20, 08 - compcache-0.1 Released!
- Feb 14, 08 - TLSFAllocator - Performance evaluation of TLSF
allocator.
- Jan 24, 08 - SwapReplayDesign - Design and usage information.
Work on allocator continues.
- Jan 09, 08 - SwapReplay
sub-project now functional! Will post some documentation soon.
- Dec
21, 07 - Now compcache can dynamically resize - pages are allocated on
demand and freed when not required. For now, compression structure is
not yet implemented i.e. compressed page still requires 1 page for
storage. Compression structure (heart of this project!) is currently
under design.
Thanks to John McCabe-Dansted and Nai Xia
for their testing efforts.
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