Replying to Avatar C-Otto 🔸

I think this function is only used for two files (some private file, and some tor cookie). I'm interested in the read accesses for block data, as this causes load on the system. The way it currently works, using some defaults and OS magic, is fine - but I'd like to tweak things (and learn, and have fun) if possible. For example, if I configure a blocksize of 1 MByte with ZFS, if then bitcoind just reads (and needs) 128 byte out of this chunk, this would cause ZFS to read 8000x the requested size from disk.
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𝟭𝗨𝗣 2y ago

I see, that makes sense. Reading in 128 byte segments would be very slow, I don't know what I was thinking. 😅

I found another clue:

/** The pre-allocation chunk size for blk?????.dat files (since 0.8) */

static const unsigned int BLOCKFILE_CHUNK_SIZE = 0x1000000; // 16 MiB

/** The pre-allocation chunk size for rev?????.dat files (since 0.8) */

static const unsigned int UNDOFILE_CHUNK_SIZE = 0x100000; // 1 MiB

/** The maximum size of a blk?????.dat file (since 0.8) */

static const unsigned int MAX_BLOCKFILE_SIZE = 0x8000000; // 128 MiB

It should be closer to the real answer I hope. It's indeed fun to find out the internals of such program like bitcoind.

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