continuwuity/src/database/pool/configure.rs

use std::{ffi::OsStr, sync::Arc};

use conduwuit::{
	debug, debug_info, expected,
	utils::{
		math::usize_from_f64,
		stream,
		stream::WIDTH_LIMIT,
		sys::{compute::is_core_available, storage},
		BoolExt,
	},
	Server,
};

use super::{QUEUE_LIMIT, WORKER_LIMIT};

pub(super) fn configure(server: &Arc<Server>) -> (usize, Vec<usize>, Vec<usize>) {
	let config = &server.config;

	// This finds the block device and gathers all the properties we need.
	let (device_name, device_prop) = config
		.db_pool_affinity
		.and_then(|| storage::name_from_path(&config.database_path))
		.map(|device_name| (device_name.clone(), storage::parallelism(&device_name)))
		.unzip();

	// The default worker count is masked-on if we didn't find better information.
	let default_worker_count = device_prop
		.as_ref()
		.is_none_or(|prop| prop.mq.is_empty())
		.then_some(config.db_pool_workers);

	// Determine the worker groupings. Each indice represents a hardware queue and
	// contains the number of workers which will service it.
	let worker_counts: Vec<_> = device_prop
		.iter()
		.map(|dev| &dev.mq)
		.flat_map(|mq| mq.iter())
		.filter(|mq| mq.cpu_list.iter().copied().any(is_core_available))
		.map(|mq| {
			mq.nr_tags.unwrap_or_default().min(
				config.db_pool_workers_limit.saturating_mul(
					mq.cpu_list
						.iter()
						.filter(|&&id| is_core_available(id))
						.count()
						.max(1),
				),
			)
		})
		.chain(default_worker_count)
		.collect();

	// Determine our software queue size for each hardware queue. This is the mpmc
	// between the tokio worker and the pool worker.
	let queue_sizes: Vec<_> = worker_counts
		.iter()
		.map(|worker_count| {
			worker_count
				.saturating_mul(config.db_pool_queue_mult)
				.clamp(QUEUE_LIMIT.0, QUEUE_LIMIT.1)
		})
		.collect();

	// Determine the CPU affinities of each hardware queue. Each indice is a cpu and
	// each value is the associated hardware queue. There is a little shiftiness
	// going on because cpu's which are not available to the process are filtered
	// out, similar to the worker_counts.
	let topology = device_prop
		.iter()
		.map(|dev| &dev.mq)
		.flat_map(|mq| mq.iter())
		.fold(vec![0; 128], |mut topology, mq| {
			mq.cpu_list
				.iter()
				.filter(|&&id| is_core_available(id))
				.for_each(|&id| {
					topology[id] = mq.id;
				});

			topology
		});

	// Regardless of the capacity of all queues we establish some limit on the total
	// number of workers; this is hopefully hinted by nr_requests.
	let max_workers = device_prop
		.as_ref()
		.and_then(|prop| prop.nr_requests)
		.unwrap_or(WORKER_LIMIT.1);

	// Determine the final worker count which we'll be spawning.
	let total_workers = worker_counts
		.iter()
		.sum::<usize>()
		.clamp(WORKER_LIMIT.0, max_workers);

	// After computing all of the above we can update the global automatic stream
	// width, hopefully with a better value tailored to this system.
	if config.stream_width_scale > 0.0 {
		let num_queues = queue_sizes.len();
		update_stream_width(server, num_queues, total_workers);
	}

	debug_info!(
		device_name = ?device_name
			.as_deref()
			.and_then(OsStr::to_str)
			.unwrap_or("None"),
		?worker_counts,
		?queue_sizes,
		?total_workers,
		stream_width = ?stream::automatic_width(),
		"Frontend topology",
	);

	(total_workers, queue_sizes, topology)
}

#[allow(clippy::as_conversions, clippy::cast_precision_loss)]
fn update_stream_width(server: &Arc<Server>, num_queues: usize, total_workers: usize) {
	let config = &server.config;
	let scale: f64 = config.stream_width_scale.min(100.0).into();
	let req_width = expected!(total_workers / num_queues).next_multiple_of(2);
	let req_width = req_width as f64;
	let req_width = usize_from_f64(req_width * scale)
		.expect("failed to convert f64 to usize")
		.clamp(WIDTH_LIMIT.0, WIDTH_LIMIT.1);

	let (old_width, new_width) = stream::set_width(req_width);
	debug!(
		scale = ?config.stream_width_scale,
		?num_queues,
		?req_width,
		?old_width,
		?new_width,
		"Updated global stream width"
	);
}