Linux Compressed Cache / News: Recent posts

The 0.20pre1 version of Compressed Cache is out. This version has some minor changes regarding parameters to determine the cache size and some /proc and /proc/sys/vm/comp_cache changes.

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.10-0.20pre1.bz2

A small fix was needed in order to compile 2.4.10-0.19 without Compressed Swap support (CONFIG_COMP_SWAP). The 2.4.10-0.19 patch has been uploaded again and now compiles even if you don't want to swap out pages in compressed form.

There's a new patch out there. Besides one fix which would cause a BUG() when freeing some pages, the patch has been updated to 2.4.10 version of Linux Kernel.

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.10-0.19.bz2

The version just released for 2.4.9, ie 0.19, has also been ported to the lastest version of Alan Cox kernel branch.

Changelog:
http://sourceforge.net/project/shownotes.php?release_id=54914

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.9ac16-0.19.bz2

Finally the new patch is out. After a _long_ time working hard on the its (un)stability and 5 pre versions, we could come up with this new version. At least in our tests the code seems to be stable. A fix for memory corruption due to a bug in our asynchronous swap and shmem corruption are among many other fixes. I think it's worth giving a try and if you notice something wrong, please tell us. This version aims to have a stable code, not performance yet, so we have not performed statistics related to performance issues.... read more

The new patch is out. This version features lots of bug fixes, but it is not stable in order to be a final version. Have a look at the huge change log to know what has changed.

Changelog:
http://sourceforge.net/project/shownotes.php?release_id=51703

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.9-0.19pre5.bz2

This shared memory bug has been so far the bug that I have spent more time to find. I couldn't figure out what the hell was going on there. I don't think it's worth to tell all I did trying to make it work (yes, I don't want to tell all the work I had in vain :-). Yesterday I was about to give up when I had the idea to test it in VMware and thus I would have kdb to play with.

Compiled for VMware, I booted the kernel. I typed shm-stress and ran it, expecting, as usual, some "Child XXX exited with signal 11" message or an error regarding wrong contents in the page. But unbelievable: no error messages at all after compressing about 2 million pages. ... read more

Up to 2.4.8 version of Linux Kernel, Compressed Cache was running reasonably well. Nevertheless, its performance has dropped terribly after upgrading to 2.4.9. In 2.4.9ac3, it is somewhat slow, but not so much as in vanilla. That's something I'd like to have fixed before releasing the 0.19 version.

The tests that I have run to detect this performance lose were the fillmem and mmap from Memtest suite. In the previous version, 2.4.8 (under UML), we took from 15 to 20 seconds to perform "./fillmem 40". In the case of 2.4.9, the same code performs in about 45 sec in the first time and the next times takes over 1m30s to finish. And in 2.4.9ac3 I got about 28 sec to have the same test run.... read more

Same version as 2.4.9-0.19pre4, it features the shared memory "fix". There's no fix at all, since it seems to be an UML bug, but this version has some minor changes.

Changelog:
http://sourceforge.net/project/shownotes.php?release_id=50315

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.9ac3-0.19pre4.bz2

The 0.19pre3 version of Compressed Cache patch for 2.4.9 is out. There's no major changes. Shared Memory is supposed to work, since it works very well in VMware and on real machine, but it stills returns error when running under UML. Minor changes regarding *lookup_comp_cache functions.

Changelog:
http://sourceforge.net/project/shownotes.php?release_id=50313

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.9-0.19pre4.bz2

The 0.19pre3 version of Compressed Cache patch is out. This version is for Linux 2.4.9 and has a bugfix with respect to the "VM: undead swap entry" error messages.

Changelog and Notes:
http://sourceforge.net/project/shownotes.php?release_id=48824

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.9-0.19pre3.bz2

Same version as 2.4.7-0.19pre2, but for 2.4.7ac11 version of Linux Kernel.

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.7ac11-0.19pre2.bz2

The 0.19pre2 version of Compressed Cache for 2.4.7 Linux Kernel is out. Besides lots of bug fixes, it has support to compressed swap pages, that will only delay the decompression (no space and IO gain). There's a directory in mm/ called comp_cache/ where the former comp_cache.c has been splitted into many files.

Unfortunatelly this is a Brown Paper Bag version, since it has some serious bugs. First of all, it has been found out that shared memory support is BROKEN. Well, and for a long time, because I tested 2.4.5 + comp_cache and it was broken as well. To test it, you can run shmem-stress from Memtest suit. Also there's a bug related to compression algorithm switch. For some reason, when switching often the algorithms, it oops in any of WK*_compress(). I think it's a race when marking which algorithm has been used to compress. Both bugs are serious but that aren't reached easily since shmem is not very much used and I think nobody will change the compression algorithm so fast to reach that possible race.... read more

Same version as 2.4.7-0.19pre1, this patch is for ac4
version of 2.4.7 Linux Kernel. Download it from here:

http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.7ac4-0.19pre1.bz2

The 0.19pre1 version of Compressed Cache patch is out. It has only two bug fixes that were bothering me when testing on real machines. It has been tested intensively on a real machine, but there are more tests to come.

Download:
http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.7-0.19pre1.bz2

Notes and Changelog:
http://sourceforge.net/project/shownotes.php?release_id=43804

Same version as 2.4.7-0.18, this patch if for ac3 version of 2.4.7 Linux Kernel. Download it from here:

http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.7ac3-0.18.bz2

A new kind of patches is available on our project page. After a feature request with respect to patches for AC kernels (Alan Cox branch of Linux Kernel), a new section was created in our download sections, namely "Kernel Patches (for AC)" where we are going to do our best to keep it up with AC kernels. You can check all paches for AC kernels on:

http://sourceforge.net/project/showfiles.php?group_id=13472

Patch 0.18 is out. As 0.18pre3, its major feature is the virtual swap address. It has some bug fixes and improvements in comparison with the last patch, namely 0.18pre3 and it's worth to give a try. Its stability has not been tested hardly and there's no idea of this virtual swap address impact over performance.

Download: http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.7-0.18.bz2... read more

The 0.18pre3 version of Compressed Cache patch is out. Now we have virtual swap address implemented, but not yet tuned and this is the major feature of this version. This virtual swap address will enable us to fix a problem we had with the current implementation: it did not work on swap less systems as well as it decreased memory size. It has to be much tested and improved, but the first version of this fix is there. Download it from here:... read more

Gian-Carlo Pascutto has run some tests on his machine and send the results to our mailing-list. They are already online on our statistics page. His tests shows how the compression algorithms are doing currently, with our current patch. Check the data out:

http://linuxcompressed.sourceforge.net/statistics/prototype3-3.html

This is the fix for 0.18pre2 compilation error:

--- mm/minilzo.c~ Tue Jul 17 18:16:18 2001
+++ mm/minilzo.c Tue Jul 17 20:51:38 2001
@@ -74,7 +74,7 @@

#if !defined(LZO_HAVE_CONFIG_H)
# include <stddef.h>
-# include <string.h>
+# include <linux/string.h>
# if !defined(NO_STDLIB_H)
# include <stdlib.h>
# endif

Gian-Carlo Pascutto ran some tests on his Athlon 1 GHz and came up with interesting results. Check them on:

http://linuxcompressed.sourceforge.net/statistics/prototype3-3.html

New patch is out. In this version, the support for all algorithms is fixed and they can be switched on the fly. Also you have the new version of LZO compression algorithm. Our old 1.04 version has been updated to 1.07. Download it from here:

http://prdownloads.sourceforge.net/linuxcompressed/patch-comp-cache-2.4.6-0.18pre2.bz2

And its changelog is available on:

http://sourceforge.net/project/shownotes.php?group_id=13472&release_id=43957

Livio Baldini Soares ran some tests on his old 486, to see how it would do with the compressed cache kernel. He tests were the Memtest Suite that we have usually tested and he also compiled the kernel (2.2.19). Results very interesting, have you a look at it:

http://linuxcompressed.sourceforge.net/statistics/prototype3-4.html

We compiled the 2.4.6 kernel on our test machine and its results may be found on:

http://linuxcompressed.sourceforge.net/statistics/prototype3-2.html