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https://github.com/eledio-devices/thirdparty-littlefs.git
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126ef8b07f
This implements the second step of full dynamic wear-leveling, block allocation randomization. This is the key part the uniformly distributes wear across the filesystem, even through reboots. The entropy actually comes from the filesystem itself, by xoring together all of the CRCs in the metadata-pairs on the filesystem. While this sounds like a ridiculous operation, it's easy to do when we already scan the metadata-pairs at mount time. This gives us a random number we can use for block allocation. Unfortunately it's not a great general purpose random generator as the output only changes every filesystem write. Fortunately that's exactly when we need our allocator. --- Additionally, the randomization created a mess for the testing framework. Fortunately, this method of randomization is deterministic. A very useful property for reproducing bugs.
31 lines
805 B
Python
Executable File
31 lines
805 B
Python
Executable File
#!/usr/bin/env python
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import struct
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import sys
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import time
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import os
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import re
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def main():
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with open('blocks/.config') as file:
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s = struct.unpack('<LLLL', file.read())
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print 'read_size: %d' % s[0]
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print 'prog_size: %d' % s[1]
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print 'block_size: %d' % s[2]
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print 'block_size: %d' % s[3]
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print 'real_size: %d' % sum(
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os.path.getsize(os.path.join('blocks', f))
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for f in os.listdir('blocks') if re.match('\d+', f))
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with open('blocks/.stats') as file:
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s = struct.unpack('<QQQ', file.read())
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print 'read_count: %d' % s[0]
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print 'prog_count: %d' % s[1]
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print 'erase_count: %d' % s[2]
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print 'runtime: %.3f' % (time.time() - os.stat('blocks').st_ctime)
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if __name__ == "__main__":
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main(*sys.argv[1:])
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