Detailed Description

Configuration for the reactor.

#include <seastar/core/reactor_config.hh>

Inheritance diagram for seastar::reactor_options:

Public Types
using	value_list_type = boost::intrusive::list< basic_value, boost::intrusive::base_hook< list_base_hook >, boost::intrusive::constant_time_size< false > >

using	option_group_list_type = boost::intrusive::list< option_group, boost::intrusive::base_hook< list_base_hook >, boost::intrusive::constant_time_size< false > >

Public Member Functions
	operator bool () const
	Does the option group has any values contained in it?

bool	used () const

const std::string &	name () const

const value_list_type &	values () const

value_list_type &	values ()

void	describe (options_descriptor &descriptor) const

void	mutate (options_mutator &mutator)

Public Attributes
program_options::selection_value< network_stack_factory >	network_stack
	Select network stack to use. More...

program_options::value	poll_mode
	Poll continuously (100% cpu use).

program_options::value< unsigned >	idle_poll_time_us
	Idle polling time in microseconds. More...

program_options::value< bool >	poll_aio
	Busy-poll for disk I/O. More...

program_options::value< double >	task_quota_ms
	Max time (ms) between polls. More...

program_options::value< double >	io_latency_goal_ms
	Max time (ms) IO operations must take. More...

program_options::value< unsigned >	max_task_backlog
	Maximum number of task backlog to allow. More...

program_options::value< unsigned >	blocked_reactor_notify_ms
	Threshold in milliseconds over which the reactor is considered blocked if no progress is made. More...

program_options::value< unsigned >	blocked_reactor_reports_per_minute
	Maximum number of backtraces reported by stall detector per minute. More...

program_options::value< bool >	blocked_reactor_report_format_oneline
	Print a simplified backtrace on a single line. More...

program_options::value	relaxed_dma
	Allow using buffered I/O if DMA is not available (reduces performance).

program_options::value< bool >	linux_aio_nowait
	Use the Linux NOWAIT AIO feature, which reduces reactor stalls due to aio (autodetected).

program_options::value< bool >	unsafe_bypass_fsync
	Bypass fsync(), may result in data loss. More...

program_options::value< bool >	kernel_page_cache
	Use the kernel page cache. More...

program_options::value	overprovisioned
	Run in an overprovisioned environment (such as docker or a laptop). More...

program_options::value	abort_on_seastar_bad_alloc
	Abort when seastar allocator cannot allocate memory.

program_options::value< bool >	force_aio_syscalls
	Force `io_getevents(2)` to issue a system call, instead of bypassing the kernel when possible. More...

program_options::value< memory::alloc_failure_kind >	dump_memory_diagnostics_on_alloc_failure_kind
	Dump diagnostics of the seastar allocator state on allocation failure. More...

program_options::selection_value< reactor_backend_selector >	reactor_backend
	Internal reactor implementation. More...

program_options::value< bool >	aio_fsync
	Use Linux aio for fsync() calls. More...

program_options::value< unsigned >	max_networking_io_control_blocks
	Maximum number of I/O control blocks (IOCBs) to allocate per shard. More...

program_options::value	heapprof
	Enable seastar heap profiling. More...

program_options::value	no_handle_interrupt
	Ignore SIGINT (for gdb).

Member Function Documentation

◆ describe()

void seastar::program_options::option_group::describe ( options_descriptor & descriptor ) const

inherited

Describe the content of this option group to the visitor.

The content is visited in a depth-first manner:

First the option groups itself is visited with options_descriptor::visit_group_start(). If this returns false the entire content of the group, including all its subgroups and values are skipped and options_descriptor::visit_group_end() is called immediately. Otherwise visiting the content of the group proceeds.
All the values contained therein are visited. For each value the following happens:
- First options_descriptor::visit_value_metadata() is called with generic metadata that all values have. If this return false the value is skipped, otherwise visiting the value proceeds.
- Then the appropriate overload of options_descriptor::visit_value() is called, with a pointer to the default value of the respective value. The pointer is null if there is no default value.
- For selection_value, options_descriptor::visit_selection_value() will be called instead of options_descriptor::visit_value(). After the value is visited, the option_group instance belonging to each candidate (if set) will be visited.
All the nested option_group instances in the current group are visited.
Finally options_descriptor::visit_group_end() is called.

◆ mutate()

void seastar::program_options::option_group::mutate ( options_mutator & mutator )

inherited

Mutate the content of this option group by the visitor.

The visiting algorithm is identical to that of describe(), with the following differences:

options_mutator::visit_value() is allowed to mutate the value through the passed-in reference. It should return true if it did so and false otherwise.
When visiting a selection value, only the nested group belonging to the selected value is visited afterwards.

Member Data Documentation

◆ aio_fsync

program_options::value<bool> seastar::reactor_options::aio_fsync

Use Linux aio for fsync() calls.

This reduces latency. Requires Linux 4.18 or later.

◆ blocked_reactor_notify_ms

program_options::value<unsigned> seastar::reactor_options::blocked_reactor_notify_ms

Threshold in milliseconds over which the reactor is considered blocked if no progress is made.

Default: 25.

◆ blocked_reactor_report_format_oneline

program_options::value<bool> seastar::reactor_options::blocked_reactor_report_format_oneline

Print a simplified backtrace on a single line.

Default: true.

◆ blocked_reactor_reports_per_minute

program_options::value<unsigned> seastar::reactor_options::blocked_reactor_reports_per_minute

Maximum number of backtraces reported by stall detector per minute.

Default: 5.

◆ dump_memory_diagnostics_on_alloc_failure_kind

program_options::value<memory::alloc_failure_kind> seastar::reactor_options::dump_memory_diagnostics_on_alloc_failure_kind

Dump diagnostics of the seastar allocator state on allocation failure.

See memory::alloc_failure_kind for allowed values. The diagnostics will be written to the seastar_memory logger, with error level. Default: memory::alloc_failure_kind::critical.

Note: Even if the seastar_memory logger is set to debug or trace level, the diagnostics will be logged irrespective of this setting.

◆ force_aio_syscalls

program_options::value<bool> seastar::reactor_options::force_aio_syscalls

Force io_getevents(2) to issue a system call, instead of bypassing the kernel when possible.

This makes strace output more useful, but slows down the application. Default: false.

◆ heapprof

program_options::value seastar::reactor_options::heapprof

Enable seastar heap profiling.

Note: Unused when seastar was compiled without heap profiling support.

◆ idle_poll_time_us

program_options::value<unsigned> seastar::reactor_options::idle_poll_time_us

Idle polling time in microseconds.

Reduce for overprovisioned environments or laptops.

◆ io_latency_goal_ms

program_options::value<double> seastar::reactor_options::io_latency_goal_ms

Max time (ms) IO operations must take.

Default: 1.5 * task_quota_ms value

◆ kernel_page_cache

program_options::value<bool> seastar::reactor_options::kernel_page_cache

Use the kernel page cache.

This disables DMA (O_DIRECT). Useful for short-lived functional tests with a small data set. Default: false.

◆ max_networking_io_control_blocks

program_options::value<unsigned> seastar::reactor_options::max_networking_io_control_blocks

Maximum number of I/O control blocks (IOCBs) to allocate per shard.

This translates to the number of sockets supported per shard. Requires tuning /proc/sys/fs/aio-max-nr. Only valid for the linux-aio reactor backend (see reactor_backend).

Default: 10000.

◆ max_task_backlog

program_options::value<unsigned> seastar::reactor_options::max_task_backlog

Maximum number of task backlog to allow.

When the number of tasks grow above this, we stop polling (e.g. I/O) until it goes back below the limit. Default: 1000.

◆ network_stack

program_options::selection_value<network_stack_factory> seastar::reactor_options::network_stack

Select network stack to use.

Each network stack has it corresponding program_options::option_group to further tune it. The available stacks are:

Posix stack (default) - no tunable options;
Native stack - net::native_stack_options;

◆ overprovisioned

program_options::value seastar::reactor_options::overprovisioned

Run in an overprovisioned environment (such as docker or a laptop).

Equivalent to:

◆ poll_aio

program_options::value<bool> seastar::reactor_options::poll_aio

Busy-poll for disk I/O.

Reduces latency and increases throughput.

◆ reactor_backend

program_options::selection_value<reactor_backend_selector> seastar::reactor_options::reactor_backend

Internal reactor implementation.

Available backends:

linux-aio
epoll
io_uring

Default: linux-aio (if available).

◆ task_quota_ms

program_options::value<double> seastar::reactor_options::task_quota_ms

Max time (ms) between polls.

Default: 0.5.

◆ unsafe_bypass_fsync

program_options::value<bool> seastar::reactor_options::unsafe_bypass_fsync

Bypass fsync(), may result in data loss.

Use for testing on consumer drives. Default: false.

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

seastar/core/reactor_config.hh