xemu/include/block/aio.h
Nicolas Saenz Julienne 71ad4713cc util/event-loop-base: Introduce options to set the thread pool size
The thread pool regulates itself: when idle, it kills threads until
empty, when in demand, it creates new threads until full. This behaviour
doesn't play well with latency sensitive workloads where the price of
creating a new thread is too high. For example, when paired with qemu's
'-mlock', or using safety features like SafeStack, creating a new thread
has been measured take multiple milliseconds.

In order to mitigate this let's introduce a new 'EventLoopBase'
property to set the thread pool size. The threads will be created during
the pool's initialization or upon updating the property's value, remain
available during its lifetime regardless of demand, and destroyed upon
freeing it. A properly characterized workload will then be able to
configure the pool to avoid any latency spikes.

Signed-off-by: Nicolas Saenz Julienne <nsaenzju@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Acked-by: Markus Armbruster <armbru@redhat.com>
Message-id: 20220425075723.20019-4-nsaenzju@redhat.com
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
2022-05-09 10:43:23 +01:00

783 lines
25 KiB
C

/*
* QEMU aio implementation
*
* Copyright IBM, Corp. 2008
*
* Authors:
* Anthony Liguori <aliguori@us.ibm.com>
*
* This work is licensed under the terms of the GNU GPL, version 2. See
* the COPYING file in the top-level directory.
*
*/
#ifndef QEMU_AIO_H
#define QEMU_AIO_H
#ifdef CONFIG_LINUX_IO_URING
#include <liburing.h>
#endif
#include "qemu/coroutine.h"
#include "qemu/queue.h"
#include "qemu/event_notifier.h"
#include "qemu/thread.h"
#include "qemu/timer.h"
typedef struct BlockAIOCB BlockAIOCB;
typedef void BlockCompletionFunc(void *opaque, int ret);
typedef struct AIOCBInfo {
void (*cancel_async)(BlockAIOCB *acb);
AioContext *(*get_aio_context)(BlockAIOCB *acb);
size_t aiocb_size;
} AIOCBInfo;
struct BlockAIOCB {
const AIOCBInfo *aiocb_info;
BlockDriverState *bs;
BlockCompletionFunc *cb;
void *opaque;
int refcnt;
};
void *qemu_aio_get(const AIOCBInfo *aiocb_info, BlockDriverState *bs,
BlockCompletionFunc *cb, void *opaque);
void qemu_aio_unref(void *p);
void qemu_aio_ref(void *p);
typedef struct AioHandler AioHandler;
typedef QLIST_HEAD(, AioHandler) AioHandlerList;
typedef void QEMUBHFunc(void *opaque);
typedef bool AioPollFn(void *opaque);
typedef void IOHandler(void *opaque);
struct Coroutine;
struct ThreadPool;
struct LinuxAioState;
struct LuringState;
/* Is polling disabled? */
bool aio_poll_disabled(AioContext *ctx);
/* Callbacks for file descriptor monitoring implementations */
typedef struct {
/*
* update:
* @ctx: the AioContext
* @old_node: the existing handler or NULL if this file descriptor is being
* monitored for the first time
* @new_node: the new handler or NULL if this file descriptor is being
* removed
*
* Add/remove/modify a monitored file descriptor.
*
* Called with ctx->list_lock acquired.
*/
void (*update)(AioContext *ctx, AioHandler *old_node, AioHandler *new_node);
/*
* wait:
* @ctx: the AioContext
* @ready_list: list for handlers that become ready
* @timeout: maximum duration to wait, in nanoseconds
*
* Wait for file descriptors to become ready and place them on ready_list.
*
* Called with ctx->list_lock incremented but not locked.
*
* Returns: number of ready file descriptors.
*/
int (*wait)(AioContext *ctx, AioHandlerList *ready_list, int64_t timeout);
/*
* need_wait:
* @ctx: the AioContext
*
* Tell aio_poll() when to stop userspace polling early because ->wait()
* has fds ready.
*
* File descriptor monitoring implementations that cannot poll fd readiness
* from userspace should use aio_poll_disabled() here. This ensures that
* file descriptors are not starved by handlers that frequently make
* progress via userspace polling.
*
* Returns: true if ->wait() should be called, false otherwise.
*/
bool (*need_wait)(AioContext *ctx);
} FDMonOps;
/*
* Each aio_bh_poll() call carves off a slice of the BH list, so that newly
* scheduled BHs are not processed until the next aio_bh_poll() call. All
* active aio_bh_poll() calls chain their slices together in a list, so that
* nested aio_bh_poll() calls process all scheduled bottom halves.
*/
typedef QSLIST_HEAD(, QEMUBH) BHList;
typedef struct BHListSlice BHListSlice;
struct BHListSlice {
BHList bh_list;
QSIMPLEQ_ENTRY(BHListSlice) next;
};
typedef QSLIST_HEAD(, AioHandler) AioHandlerSList;
struct AioContext {
GSource source;
/* Used by AioContext users to protect from multi-threaded access. */
QemuRecMutex lock;
/* The list of registered AIO handlers. Protected by ctx->list_lock. */
AioHandlerList aio_handlers;
/* The list of AIO handlers to be deleted. Protected by ctx->list_lock. */
AioHandlerList deleted_aio_handlers;
/* Used to avoid unnecessary event_notifier_set calls in aio_notify;
* only written from the AioContext home thread, or under the BQL in
* the case of the main AioContext. However, it is read from any
* thread so it is still accessed with atomic primitives.
*
* If this field is 0, everything (file descriptors, bottom halves,
* timers) will be re-evaluated before the next blocking poll() or
* io_uring wait; therefore, the event_notifier_set call can be
* skipped. If it is non-zero, you may need to wake up a concurrent
* aio_poll or the glib main event loop, making event_notifier_set
* necessary.
*
* Bit 0 is reserved for GSource usage of the AioContext, and is 1
* between a call to aio_ctx_prepare and the next call to aio_ctx_check.
* Bits 1-31 simply count the number of active calls to aio_poll
* that are in the prepare or poll phase.
*
* The GSource and aio_poll must use a different mechanism because
* there is no certainty that a call to GSource's prepare callback
* (via g_main_context_prepare) is indeed followed by check and
* dispatch. It's not clear whether this would be a bug, but let's
* play safe and allow it---it will just cause extra calls to
* event_notifier_set until the next call to dispatch.
*
* Instead, the aio_poll calls include both the prepare and the
* dispatch phase, hence a simple counter is enough for them.
*/
uint32_t notify_me;
/* A lock to protect between QEMUBH and AioHandler adders and deleter,
* and to ensure that no callbacks are removed while we're walking and
* dispatching them.
*/
QemuLockCnt list_lock;
/* Bottom Halves pending aio_bh_poll() processing */
BHList bh_list;
/* Chained BH list slices for each nested aio_bh_poll() call */
QSIMPLEQ_HEAD(, BHListSlice) bh_slice_list;
/* Used by aio_notify.
*
* "notified" is used to avoid expensive event_notifier_test_and_clear
* calls. When it is clear, the EventNotifier is clear, or one thread
* is going to clear "notified" before processing more events. False
* positives are possible, i.e. "notified" could be set even though the
* EventNotifier is clear.
*
* Note that event_notifier_set *cannot* be optimized the same way. For
* more information on the problem that would result, see "#ifdef BUG2"
* in the docs/aio_notify_accept.promela formal model.
*/
bool notified;
EventNotifier notifier;
QSLIST_HEAD(, Coroutine) scheduled_coroutines;
QEMUBH *co_schedule_bh;
int thread_pool_min;
int thread_pool_max;
/* Thread pool for performing work and receiving completion callbacks.
* Has its own locking.
*/
struct ThreadPool *thread_pool;
#ifdef CONFIG_LINUX_AIO
/*
* State for native Linux AIO. Uses aio_context_acquire/release for
* locking.
*/
struct LinuxAioState *linux_aio;
#endif
#ifdef CONFIG_LINUX_IO_URING
/*
* State for Linux io_uring. Uses aio_context_acquire/release for
* locking.
*/
struct LuringState *linux_io_uring;
/* State for file descriptor monitoring using Linux io_uring */
struct io_uring fdmon_io_uring;
AioHandlerSList submit_list;
#endif
/* TimerLists for calling timers - one per clock type. Has its own
* locking.
*/
QEMUTimerListGroup tlg;
int external_disable_cnt;
/* Number of AioHandlers without .io_poll() */
int poll_disable_cnt;
/* Polling mode parameters */
int64_t poll_ns; /* current polling time in nanoseconds */
int64_t poll_max_ns; /* maximum polling time in nanoseconds */
int64_t poll_grow; /* polling time growth factor */
int64_t poll_shrink; /* polling time shrink factor */
/* AIO engine parameters */
int64_t aio_max_batch; /* maximum number of requests in a batch */
/*
* List of handlers participating in userspace polling. Protected by
* ctx->list_lock. Iterated and modified mostly by the event loop thread
* from aio_poll() with ctx->list_lock incremented. aio_set_fd_handler()
* only touches the list to delete nodes if ctx->list_lock's count is zero.
*/
AioHandlerList poll_aio_handlers;
/* Are we in polling mode or monitoring file descriptors? */
bool poll_started;
/* epoll(7) state used when built with CONFIG_EPOLL */
int epollfd;
const FDMonOps *fdmon_ops;
};
/**
* aio_context_new: Allocate a new AioContext.
*
* AioContext provide a mini event-loop that can be waited on synchronously.
* They also provide bottom halves, a service to execute a piece of code
* as soon as possible.
*/
AioContext *aio_context_new(Error **errp);
/**
* aio_context_ref:
* @ctx: The AioContext to operate on.
*
* Add a reference to an AioContext.
*/
void aio_context_ref(AioContext *ctx);
/**
* aio_context_unref:
* @ctx: The AioContext to operate on.
*
* Drop a reference to an AioContext.
*/
void aio_context_unref(AioContext *ctx);
/* Take ownership of the AioContext. If the AioContext will be shared between
* threads, and a thread does not want to be interrupted, it will have to
* take ownership around calls to aio_poll(). Otherwise, aio_poll()
* automatically takes care of calling aio_context_acquire and
* aio_context_release.
*
* Note that this is separate from bdrv_drained_begin/bdrv_drained_end. A
* thread still has to call those to avoid being interrupted by the guest.
*
* Bottom halves, timers and callbacks can be created or removed without
* acquiring the AioContext.
*/
void aio_context_acquire(AioContext *ctx);
/* Relinquish ownership of the AioContext. */
void aio_context_release(AioContext *ctx);
/**
* aio_bh_schedule_oneshot_full: Allocate a new bottom half structure that will
* run only once and as soon as possible.
*
* @name: A human-readable identifier for debugging purposes.
*/
void aio_bh_schedule_oneshot_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
const char *name);
/**
* aio_bh_schedule_oneshot: Allocate a new bottom half structure that will run
* only once and as soon as possible.
*
* A convenience wrapper for aio_bh_schedule_oneshot_full() that uses cb as the
* name string.
*/
#define aio_bh_schedule_oneshot(ctx, cb, opaque) \
aio_bh_schedule_oneshot_full((ctx), (cb), (opaque), (stringify(cb)))
/**
* aio_bh_new_full: Allocate a new bottom half structure.
*
* Bottom halves are lightweight callbacks whose invocation is guaranteed
* to be wait-free, thread-safe and signal-safe. The #QEMUBH structure
* is opaque and must be allocated prior to its use.
*
* @name: A human-readable identifier for debugging purposes.
*/
QEMUBH *aio_bh_new_full(AioContext *ctx, QEMUBHFunc *cb, void *opaque,
const char *name);
/**
* aio_bh_new: Allocate a new bottom half structure
*
* A convenience wrapper for aio_bh_new_full() that uses the cb as the name
* string.
*/
#define aio_bh_new(ctx, cb, opaque) \
aio_bh_new_full((ctx), (cb), (opaque), (stringify(cb)))
/**
* aio_notify: Force processing of pending events.
*
* Similar to signaling a condition variable, aio_notify forces
* aio_poll to exit, so that the next call will re-examine pending events.
* The caller of aio_notify will usually call aio_poll again very soon,
* or go through another iteration of the GLib main loop. Hence, aio_notify
* also has the side effect of recalculating the sets of file descriptors
* that the main loop waits for.
*
* Calling aio_notify is rarely necessary, because for example scheduling
* a bottom half calls it already.
*/
void aio_notify(AioContext *ctx);
/**
* aio_notify_accept: Acknowledge receiving an aio_notify.
*
* aio_notify() uses an EventNotifier in order to wake up a sleeping
* aio_poll() or g_main_context_iteration(). Calls to aio_notify() are
* usually rare, but the AioContext has to clear the EventNotifier on
* every aio_poll() or g_main_context_iteration() in order to avoid
* busy waiting. This event_notifier_test_and_clear() cannot be done
* using the usual aio_context_set_event_notifier(), because it must
* be done before processing all events (file descriptors, bottom halves,
* timers).
*
* aio_notify_accept() is an optimized event_notifier_test_and_clear()
* that is specific to an AioContext's notifier; it is used internally
* to clear the EventNotifier only if aio_notify() had been called.
*/
void aio_notify_accept(AioContext *ctx);
/**
* aio_bh_call: Executes callback function of the specified BH.
*/
void aio_bh_call(QEMUBH *bh);
/**
* aio_bh_poll: Poll bottom halves for an AioContext.
*
* These are internal functions used by the QEMU main loop.
* And notice that multiple occurrences of aio_bh_poll cannot
* be called concurrently
*/
int aio_bh_poll(AioContext *ctx);
/**
* qemu_bh_schedule: Schedule a bottom half.
*
* Scheduling a bottom half interrupts the main loop and causes the
* execution of the callback that was passed to qemu_bh_new.
*
* Bottom halves that are scheduled from a bottom half handler are instantly
* invoked. This can create an infinite loop if a bottom half handler
* schedules itself.
*
* @bh: The bottom half to be scheduled.
*/
void qemu_bh_schedule(QEMUBH *bh);
/**
* qemu_bh_cancel: Cancel execution of a bottom half.
*
* Canceling execution of a bottom half undoes the effect of calls to
* qemu_bh_schedule without freeing its resources yet. While cancellation
* itself is also wait-free and thread-safe, it can of course race with the
* loop that executes bottom halves unless you are holding the iothread
* mutex. This makes it mostly useless if you are not holding the mutex.
*
* @bh: The bottom half to be canceled.
*/
void qemu_bh_cancel(QEMUBH *bh);
/**
*qemu_bh_delete: Cancel execution of a bottom half and free its resources.
*
* Deleting a bottom half frees the memory that was allocated for it by
* qemu_bh_new. It also implies canceling the bottom half if it was
* scheduled.
* This func is async. The bottom half will do the delete action at the finial
* end.
*
* @bh: The bottom half to be deleted.
*/
void qemu_bh_delete(QEMUBH *bh);
/* Return whether there are any pending callbacks from the GSource
* attached to the AioContext, before g_poll is invoked.
*
* This is used internally in the implementation of the GSource.
*/
bool aio_prepare(AioContext *ctx);
/* Return whether there are any pending callbacks from the GSource
* attached to the AioContext, after g_poll is invoked.
*
* This is used internally in the implementation of the GSource.
*/
bool aio_pending(AioContext *ctx);
/* Dispatch any pending callbacks from the GSource attached to the AioContext.
*
* This is used internally in the implementation of the GSource.
*/
void aio_dispatch(AioContext *ctx);
/* Progress in completing AIO work to occur. This can issue new pending
* aio as a result of executing I/O completion or bh callbacks.
*
* Return whether any progress was made by executing AIO or bottom half
* handlers. If @blocking == true, this should always be true except
* if someone called aio_notify.
*
* If there are no pending bottom halves, but there are pending AIO
* operations, it may not be possible to make any progress without
* blocking. If @blocking is true, this function will wait until one
* or more AIO events have completed, to ensure something has moved
* before returning.
*/
bool aio_poll(AioContext *ctx, bool blocking);
/* Register a file descriptor and associated callbacks. Behaves very similarly
* to qemu_set_fd_handler. Unlike qemu_set_fd_handler, these callbacks will
* be invoked when using aio_poll().
*
* Code that invokes AIO completion functions should rely on this function
* instead of qemu_set_fd_handler[2].
*/
void aio_set_fd_handler(AioContext *ctx,
int fd,
bool is_external,
IOHandler *io_read,
IOHandler *io_write,
AioPollFn *io_poll,
IOHandler *io_poll_ready,
void *opaque);
/* Set polling begin/end callbacks for a file descriptor that has already been
* registered with aio_set_fd_handler. Do nothing if the file descriptor is
* not registered.
*/
void aio_set_fd_poll(AioContext *ctx, int fd,
IOHandler *io_poll_begin,
IOHandler *io_poll_end);
/* Register an event notifier and associated callbacks. Behaves very similarly
* to event_notifier_set_handler. Unlike event_notifier_set_handler, these callbacks
* will be invoked when using aio_poll().
*
* Code that invokes AIO completion functions should rely on this function
* instead of event_notifier_set_handler.
*/
void aio_set_event_notifier(AioContext *ctx,
EventNotifier *notifier,
bool is_external,
EventNotifierHandler *io_read,
AioPollFn *io_poll,
EventNotifierHandler *io_poll_ready);
/* Set polling begin/end callbacks for an event notifier that has already been
* registered with aio_set_event_notifier. Do nothing if the event notifier is
* not registered.
*/
void aio_set_event_notifier_poll(AioContext *ctx,
EventNotifier *notifier,
EventNotifierHandler *io_poll_begin,
EventNotifierHandler *io_poll_end);
/* Return a GSource that lets the main loop poll the file descriptors attached
* to this AioContext.
*/
GSource *aio_get_g_source(AioContext *ctx);
/* Return the ThreadPool bound to this AioContext */
struct ThreadPool *aio_get_thread_pool(AioContext *ctx);
/* Setup the LinuxAioState bound to this AioContext */
struct LinuxAioState *aio_setup_linux_aio(AioContext *ctx, Error **errp);
/* Return the LinuxAioState bound to this AioContext */
struct LinuxAioState *aio_get_linux_aio(AioContext *ctx);
/* Setup the LuringState bound to this AioContext */
struct LuringState *aio_setup_linux_io_uring(AioContext *ctx, Error **errp);
/* Return the LuringState bound to this AioContext */
struct LuringState *aio_get_linux_io_uring(AioContext *ctx);
/**
* aio_timer_new_with_attrs:
* @ctx: the aio context
* @type: the clock type
* @scale: the scale
* @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values
* to assign
* @cb: the callback to call on timer expiry
* @opaque: the opaque pointer to pass to the callback
*
* Allocate a new timer (with attributes) attached to the context @ctx.
* The function is responsible for memory allocation.
*
* The preferred interface is aio_timer_init or aio_timer_init_with_attrs.
* Use that unless you really need dynamic memory allocation.
*
* Returns: a pointer to the new timer
*/
static inline QEMUTimer *aio_timer_new_with_attrs(AioContext *ctx,
QEMUClockType type,
int scale, int attributes,
QEMUTimerCB *cb, void *opaque)
{
return timer_new_full(&ctx->tlg, type, scale, attributes, cb, opaque);
}
/**
* aio_timer_new:
* @ctx: the aio context
* @type: the clock type
* @scale: the scale
* @cb: the callback to call on timer expiry
* @opaque: the opaque pointer to pass to the callback
*
* Allocate a new timer attached to the context @ctx.
* See aio_timer_new_with_attrs for details.
*
* Returns: a pointer to the new timer
*/
static inline QEMUTimer *aio_timer_new(AioContext *ctx, QEMUClockType type,
int scale,
QEMUTimerCB *cb, void *opaque)
{
return timer_new_full(&ctx->tlg, type, scale, 0, cb, opaque);
}
/**
* aio_timer_init_with_attrs:
* @ctx: the aio context
* @ts: the timer
* @type: the clock type
* @scale: the scale
* @attributes: 0, or one to multiple OR'ed QEMU_TIMER_ATTR_<id> values
* to assign
* @cb: the callback to call on timer expiry
* @opaque: the opaque pointer to pass to the callback
*
* Initialise a new timer (with attributes) attached to the context @ctx.
* The caller is responsible for memory allocation.
*/
static inline void aio_timer_init_with_attrs(AioContext *ctx,
QEMUTimer *ts, QEMUClockType type,
int scale, int attributes,
QEMUTimerCB *cb, void *opaque)
{
timer_init_full(ts, &ctx->tlg, type, scale, attributes, cb, opaque);
}
/**
* aio_timer_init:
* @ctx: the aio context
* @ts: the timer
* @type: the clock type
* @scale: the scale
* @cb: the callback to call on timer expiry
* @opaque: the opaque pointer to pass to the callback
*
* Initialise a new timer attached to the context @ctx.
* See aio_timer_init_with_attrs for details.
*/
static inline void aio_timer_init(AioContext *ctx,
QEMUTimer *ts, QEMUClockType type,
int scale,
QEMUTimerCB *cb, void *opaque)
{
timer_init_full(ts, &ctx->tlg, type, scale, 0, cb, opaque);
}
/**
* aio_compute_timeout:
* @ctx: the aio context
*
* Compute the timeout that a blocking aio_poll should use.
*/
int64_t aio_compute_timeout(AioContext *ctx);
/**
* aio_disable_external:
* @ctx: the aio context
*
* Disable the further processing of external clients.
*/
static inline void aio_disable_external(AioContext *ctx)
{
qatomic_inc(&ctx->external_disable_cnt);
}
/**
* aio_enable_external:
* @ctx: the aio context
*
* Enable the processing of external clients.
*/
static inline void aio_enable_external(AioContext *ctx)
{
int old;
old = qatomic_fetch_dec(&ctx->external_disable_cnt);
assert(old > 0);
if (old == 1) {
/* Kick event loop so it re-arms file descriptors */
aio_notify(ctx);
}
}
/**
* aio_external_disabled:
* @ctx: the aio context
*
* Return true if the external clients are disabled.
*/
static inline bool aio_external_disabled(AioContext *ctx)
{
return qatomic_read(&ctx->external_disable_cnt);
}
/**
* aio_node_check:
* @ctx: the aio context
* @is_external: Whether or not the checked node is an external event source.
*
* Check if the node's is_external flag is okay to be polled by the ctx at this
* moment. True means green light.
*/
static inline bool aio_node_check(AioContext *ctx, bool is_external)
{
return !is_external || !qatomic_read(&ctx->external_disable_cnt);
}
/**
* aio_co_schedule:
* @ctx: the aio context
* @co: the coroutine
*
* Start a coroutine on a remote AioContext.
*
* The coroutine must not be entered by anyone else while aio_co_schedule()
* is active. In addition the coroutine must have yielded unless ctx
* is the context in which the coroutine is running (i.e. the value of
* qemu_get_current_aio_context() from the coroutine itself).
*/
void aio_co_schedule(AioContext *ctx, struct Coroutine *co);
/**
* aio_co_reschedule_self:
* @new_ctx: the new context
*
* Move the currently running coroutine to new_ctx. If the coroutine is already
* running in new_ctx, do nothing.
*/
void coroutine_fn aio_co_reschedule_self(AioContext *new_ctx);
/**
* aio_co_wake:
* @co: the coroutine
*
* Restart a coroutine on the AioContext where it was running last, thus
* preventing coroutines from jumping from one context to another when they
* go to sleep.
*
* aio_co_wake may be executed either in coroutine or non-coroutine
* context. The coroutine must not be entered by anyone else while
* aio_co_wake() is active.
*/
void aio_co_wake(struct Coroutine *co);
/**
* aio_co_enter:
* @ctx: the context to run the coroutine
* @co: the coroutine to run
*
* Enter a coroutine in the specified AioContext.
*/
void aio_co_enter(AioContext *ctx, struct Coroutine *co);
/**
* Return the AioContext whose event loop runs in the current thread.
*
* If called from an IOThread this will be the IOThread's AioContext. If
* called from the main thread or with the "big QEMU lock" taken it
* will be the main loop AioContext.
*/
AioContext *qemu_get_current_aio_context(void);
void qemu_set_current_aio_context(AioContext *ctx);
/**
* aio_context_setup:
* @ctx: the aio context
*
* Initialize the aio context.
*/
void aio_context_setup(AioContext *ctx);
/**
* aio_context_destroy:
* @ctx: the aio context
*
* Destroy the aio context.
*/
void aio_context_destroy(AioContext *ctx);
/* Used internally, do not call outside AioContext code */
void aio_context_use_g_source(AioContext *ctx);
/**
* aio_context_set_poll_params:
* @ctx: the aio context
* @max_ns: how long to busy poll for, in nanoseconds
* @grow: polling time growth factor
* @shrink: polling time shrink factor
*
* Poll mode can be disabled by setting poll_max_ns to 0.
*/
void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,
int64_t grow, int64_t shrink,
Error **errp);
/**
* aio_context_set_aio_params:
* @ctx: the aio context
* @max_batch: maximum number of requests in a batch, 0 means that the
* engine will use its default
*/
void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch,
Error **errp);
/**
* aio_context_set_thread_pool_params:
* @ctx: the aio context
* @min: min number of threads to have readily available in the thread pool
* @min: max number of threads the thread pool can contain
*/
void aio_context_set_thread_pool_params(AioContext *ctx, int64_t min,
int64_t max, Error **errp);
#endif