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

[Nitin Gupta]

Nick Piggin wrote:
> On Tuesday 17 March 2009 22:36:46 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/

> I wonder how hard it would be to make the compression code
> use an arbitrary file or device for the storage backend rather
> than make a new block device? Then you could make a new ram
> block device that can swap its pages out (or even extend brd.c
> with that functionality, or use loop on tmpfs etc).

Its already done as mentioned in Documentation/blockdev/compcache.txt
(patch 3/3) but I should have added it here also: compcache accepts
"backing_dev" parameter for backing swap partition - this allows us to
forward any R/W request to backing swap device. Currently only poorly
compressible pages (compress length > PAGE_SIZE/2) are forwarded to
backing_dev.

Thanks,
Nitin




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