STRUCT BUCKET(9)

💖 NAME 💖

struct bucket — hash bucket. That's the whole name, bestie. This is from the Kernel API Manual, page struct bucket(9), and it's lowkey iconic.

🦋 SYNOPSIS 🦋

Here's the struct in all its glory, exactly as it appears:

       struct bucket {
           u8 first_hop;
           u8 next_hop;
           u64 key;
           void *value;
        };

💅 Members 💅

• first_hop — the biased offset of the first entry in the hop list of the neighborhood that hashes to this bucket.
• next_hop — the biased offset of the next bucket in the hop list.
• key — the key stored in this bucket.
• value — the value stored in this bucket (NULL if empty).

🌸 Description 🌸

Okay so picture this: buckets are packed together to reduce memory usage and improve cache efficiency. It would be tempting to encode the hop offsets separately and maintain alignment of key/value pairs — like, sure, Jan — but it's crucial to keep the hop fields near the buckets that use them so they'll tend to share cache lines. That's the whole point, and honestly? It ate.

🔥 SEE ALSO 🔥

• Kernel file ./drivers/md/dm-vdo/int-map.c Introduction(9)
• struct int_map(9)
• mix(9)
• hash_key(9)
• allocate_buckets(9)
• vdo_int_map_create(9)
• vdo_int_map_free(9)
• vdo_int_map_size(9)
• dereference_hop(9)
• insert_in_hop_list(9)
• select_bucket(9)
• search_hop_list(9)
• vdo_int_map_get(9)
• resize_buckets(9)
• find_empty_bucket(9)
• move_empty_bucket(9)
• update_mapping(9)
• find_or_make_vacancy(9)
• vdo_int_map_put(9)
• vdo_int_map_remove(9)

That's the tea. This page's source/version line is ./drivers/md/dm-vdo, and it's dated October 2026. struct bucket(9) out — mwah. 💖✨