seastar::fair_group Class Reference

Detailed Description

Group of queues class.

This is a fair group. It's attached by one or mode fair queues. On machines having the big* amount of shards, queues use the group to borrow/lend the needed capacity for requests dispatching.

• Big means that when all shards sumbit requests alltogether the disk is unable to dispatch them efficiently. The inability can be of two kinds – either disk cannot cope with the number of arriving requests, or the total size of the data withing the given time frame exceeds the disk throughput.

#include <seastar/core/fair_queue.hh>

Classes
struct	config

Public Types
using	capacity_t = fair_queue_entry::capacity_t
using	clock_type = std::chrono::steady_clock
using	rate_resolution = std::milli
using	token_bucket_t = internal::shared_token_bucket< capacity_t, rate_resolution, internal::capped_release::no >

Public Member Functions
auto	capacity_duration (capacity_t cap) const noexcept
	fair_group (config cfg, unsigned nr_queues)
	fair_group (fair_group &&)=delete
capacity_t	maximum_capacity () const noexcept
capacity_t	per_tick_grab_threshold () const noexcept
capacity_t	grab_capacity (capacity_t cap) noexcept
clock_type::time_point	replenished_ts () const noexcept
void	replenish_capacity (clock_type::time_point now) noexcept
void	maybe_replenish_capacity (clock_type::time_point &local_ts) noexcept
capacity_t	capacity_deficiency (capacity_t from) const noexcept
std::chrono::duration< double >	rate_limit_duration () const noexcept
const token_bucket_t &	token_bucket () const noexcept

Static Public Member Functions
static double	capacity_tokens (capacity_t cap) noexcept
static capacity_t	tokens_capacity (double tokens) noexcept

Static Public Attributes
static constexpr float	fixed_point_factor = float(1 << 24)

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Class Documentation

seastar::fair_group::config

struct seastar::fair_group::config

Class Members
sstring	label
double	limit_min_tokens
double	min_tokens
duration< double >	rate_limit_duration

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The documentation for this class was generated from the following file:

• seastar/core/fair_queue.hh