Messages in this thread | | | Date | Mon, 30 Mar 2009 20:18:02 +0530 | From | Nitin Gupta <> | Subject | [PATCH 0/3] compressed in-memory swapping take5 |
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Hi,
Project home: http://compcache.googlecode.com
It allows creating a RAM based block device which acts as swap disk. Pages swapped to this device are compressed and stored in memory itself. This is a big win over swapping to slow hard-disk which are typically used as swap disk. For flash, these suffer from wear-leveling issues when used as swap disk - so again its helpful. For swapless systems, it allows more apps to run.
* Changelog: take5 vs take4 xvmalloc changes: - Use kzalloc() instead of kmalloc() + memset(). - Remove redundant initialization of pool freelists to 0.
* Changelog: take4 vs take3 xvmalloc changes: - Fixed regression in take3 that caused ramzswap write failures. This happened due to error in find_block() where we did not do explicit cast to 'unsigned long' when checking for bits set in bitmap. Now changed it to use kernel build-in test_bit(). - Fix divide by zero error in proc read function. ramzswap changes: - Forward write requests to backing swap device if allocation for compressed page fails. - Code cleanups.
* Changelog: take3 vs take2 xvmalloc changes: - Use kernel defined macros and constants in xvmalloc and remove equivalent defines for ALIGN, roundup etc. - Use kernel bitops (set_bit, clear_bit) - Moved it to drivers/block since its not clear if it has any other user. ramzswap changes: - All instances of compcache renamed to ramzswap. Also renamed module to ramzswap - Renamed "backing_dev" parameter to "backing_swap" - Documentation changes to reflect above changes. - Remove "table index" from object header (4 bytes). This will be needed when memory defragmentation is implemented. So, avoid this (small) overhead for now.
* Changelog: take2 vs initial revision: xvmalloc changes: - Use Linux kernel coding style for xvmalloc - Collapse all individual flag test/set/get to generic {test_set_get}_flag - Added BLOCK_NEXT() macro to reach next contiguous block - Other minor cleanups - no functional changes compcache block device code: - compcache core changes due to change in xvmalloc interface names
* Testing notes: - Multiple cycles of 'scan' benchmark available at: http://linux-mm.org/PageReplacementTesting It does scans of anonymous mapped memory, both cyclic and use once.
Config: Arch: x86 and x64 CPUs: 1/2, RAM: 512MB backing swap: 768MB, ramzswap memlimit: 76MB (15% of RAM).
Continuously run 'scan' till it triggers 200K R/W operations on ramzswap. Any incompressible pages were correctly forwarded to backing swap device. cmd: ./scan 450 20 # scan over 450MB, 20 times.
- Links to more performance numbers, use cases can be found at: http://lkml.org/lkml/2009/3/17/116
Thanks to Ed Tomlinson for reporting bug in 'take3' patches and to all the reviewers.
Thanks, Nitin
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