__bfq_lookup_next_entity(9)

💖 NAME 💖

okay bestie, meet __bfq_lookup_next_entity(9) — yes, from the Kernel API Manual, and yes she is that girl. Her whole job: return the first eligible entity in @st. That's it. That's the name. 💅

✨ SYNOPSIS ✨

signature check, copy it exactly bestie:

struct bfq_entity * __bfq_lookup_next_entity (struct bfq_service_tree
*st , bool in_service );

🎀 ARGUMENTS 🎀

• st — the service tree. the tree in question.
• in_service — whether or not there is an in-service entity for the sched_data this active tree belongs to. lowkey a yes/no vibe.

🦋 DESCRIPTION 🦋

okay so picture this: if there is no in-service entity for the sched_data that st belongs to, then return the entity that will be set in service if:

1. the parent entity this st belongs to is set in service;
2. no entity belonging to such parent entity undergoes a state change that would influence the timestamps of the entity (e.g., becomes idle, becomes backlogged, changes its budget, ...).

In this first case, update the virtual time in st too (see the comments on this update inside the function). 🫶

💫 the plot twist: there is an in-service entity

in contrast, if there is an in-service entity, then return the entity that would be set in service if not only the above conditions, but also the next one held true: the currently in-service entity, on expiration,

1. gets a finish time equal to the current one, or
2. is not eligible any more, or
3. is idle.

so yeah — same mission, extra condition energy. ✨

🌸 SEE ALSO 🌸

the Kernel file ./block/bfq-wf2q.c is the home base, and the whole linked-up friend group is:

• bfq_gt(9), bfq_update_next_in_service(9), bfq_delta(9), bfq_calc_finish(9), bfq_entity_of(9)
• bfq_extract(9), bfq_idle_extract(9), bfq_insert(9), bfq_update_min(9), bfq_update_active_node(9)
• bfq_update_active_tree(9), bfq_active_insert(9), bfq_ioprio_to_weight(9), bfq_weight_to_ioprio(9), bfq_find_deepest(9)
• bfq_active_extract(9), bfq_idle_insert(9), bfq_forget_entity(9), bfq_put_idle_entity(9), bfq_forget_idle(9)
• bfq_bfqq_served(9), bfq_bfqq_charge_time(9), __bfq_activate_entity(9), __bfq_requeue_entity(9), bfq_activate_requeue_entity(9)
• __bfq_deactivate_entity(9), bfq_deactivate_entity(9), bfq_calc_vtime_jump(9), bfq_first_active_entity(9), bfq_lookup_next_entity(9)

cute little sign-off: source/version ./block, date October 2026, page __bfq_lookup_next_entity(9) — mwah, go read the kernel bestie 💋👑