[:NitinGupta:Nitin Gupta]

MailTo(nitingupta910 AT gmail DOT com)

• This page contains some prototype code developed for CompressedCaching project. After seriously insufficient testing, each of these components were eventually merged into final implementation on 2.6.x kernels.

Compression algorithms to kernel mode:

Kernel module to test de/compression algorithms (WKdm, WK4x4, LZO): attachment:compress-test.tar.gz

There are basically three main algorithms that are well studied w.r.t compressed caching by previous works -- WKdm, WK4x4, LZO.

Of these, WKdm, WK4x4 are designed to handle anon pages (non filesystem pages) while LZO is more suitable for filesystem data. (Also, in general, compression speed is in order: WKdm > WK4x4 > LZO, while compression factor order is, in general, reverse).

Now, all three algos are ported to kernel space - WKdm, WK4x4 and LZO. You can test them all using this module. It creates 3 /proc entries: /proc/compress-test/{compress, decompress, algo_idx} as described below: (for some detail see README with this module)

In short:

Write to /proc/compress-test entries:

1. compress: compress data witten to it and store in internal buffer.

2. algo_idx: write index of algo you want to test (0: WKdm, 1: WK4x4, 2: LZO)

Read from /proc/compress-test entries:

1. compress: show original and compressed size (TODO: add other stats like time taken too)

2. decompress: decompress compressed data stored in internal buffer.

3. algo_idx: shows list of algos supported with their index.

Compression Structure Implementation:

attachment:storage-test.tar.gz : This module implements compression structure as described on CompressedCaching.

• The storage begins as a single page. As you add pages to it, it expands till it reaches its max limit. As you take out pages, it shrinks, freeing up pages when it has no chunks left.
• Adjacent free chunks are merged together.
• Each page can be compressed using different algo.

Please see README for usage.

In short:

Interface is via /proc:

/proc/storage-test/{readpage, writepage, show_structure}

1. writepage: write a page on this to compress and store it in ccache.

2. readpage: write 'id' (see README) of page you want.

3. show_structure: read to show current snapshot of ccache storage.

• BR

  • BR

There was a university where computer science students could ask programming questions to faculty staff. BRBR

However, before taking their problem and question to the staff, they first had to explain their problem and ask their question to a teddy bear in the lobby. Legend has it that 90% of the students found the answer to their question after putting their problem in words, just by asking it to the teddy bear. BRBR

They never needed to ask the staff, all they needed was to organize their thoughts.BR -- picked up from kernelnewbies.org