Re: [PATCH 1/3]: compressed RAM block device

From: Nitin Gupta
Date: Fri Mar 20 2009 - 15:54:31 EST


Pavel Machek wrote:
On Tue 2009-03-17 17:06:46, Nitin Gupta wrote:
drivers/block/Kconfig | 22 +
drivers/block/Makefile | 1 +
drivers/block/compcache.c | 995 +++++++++++++++++++++++++++++++++++++++++++++
drivers/block/compcache.h | 160 ++++++++
4 files changed, 1178 insertions(+), 0 deletions(-)

Creates RAM based block device (ramzswap0) which can be used as swap device.
Pages swapped to this are compressed and stored in memory itself.

The module is called compcache.ko. It depends on:
- xvmalloc.ko: memory allocator
- lzo_compress.ko
- lzo_decompress.ko

See Documentation/blockdev/compcache.txt for usage details.

Project home: http://code.google.com/p/compcache/


Compcache is really bad name for this. zramdisk? gzrd?

It was named compcache according to its original goal:
compressed caching for anonymous _and_ filesystem caches. This ram block
device is for handling anonymous memory only. Anyway, actual block device
is called ramzswap which you might like more :)

Is the block device useful for general filesystem storage?

No. It can only handle page aligned I/O. But it shouldn't be too hard
to make it generic compressed ram disk with physical backing device support.
But unfortunately I do not have bandwidth to do this myself.

Thanks,
Nitin

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