From 7d5983e3c8c40b1d0668faba31d79905c4fadd7d Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne Date: Mon, 25 Apr 2022 09:57:21 +0200 Subject: Introduce event-loop-base abstract class Introduce the 'event-loop-base' abstract class, it'll hold the properties common to all event loops and provide the necessary hooks for their creation and maintenance. Then have iothread inherit from it. EventLoopBaseClass is defined as user creatable and provides a hook for its children to attach themselves to the user creatable class 'complete' function. It also provides an update_params() callback to propagate property changes onto its children. The new 'event-loop-base' class will live in the root directory. It is built on its own using the 'link_whole' option (there are no direct function dependencies between the class and its children, it all happens trough 'constructor' magic). And also imposes new compilation dependencies: qom <- event-loop-base <- blockdev (iothread.c) And in subsequent patches: qom <- event-loop-base <- qemuutil (util/main-loop.c) All this forced some amount of reordering in meson.build: - Moved qom build definition before qemuutil. Doing it the other way around (i.e. moving qemuutil after qom) isn't possible as a lot of core libraries that live in between the two depend on it. - Process the 'hw' subdir earlier, as it introduces files into the 'qom' source set. No functional changes intended. Signed-off-by: Nicolas Saenz Julienne Reviewed-by: Stefan Hajnoczi Acked-by: Markus Armbruster Message-id: 20220425075723.20019-2-nsaenzju@redhat.com Signed-off-by: Stefan Hajnoczi --- event-loop-base.c | 104 ++++++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 104 insertions(+) create mode 100644 event-loop-base.c (limited to 'event-loop-base.c') diff --git a/event-loop-base.c b/event-loop-base.c new file mode 100644 index 0000000..a924c73 --- /dev/null +++ b/event-loop-base.c @@ -0,0 +1,104 @@ +/* + * QEMU event-loop base + * + * Copyright (C) 2022 Red Hat Inc + * + * Authors: + * Stefan Hajnoczi + * Nicolas Saenz Julienne + * + * This work is licensed under the terms of the GNU GPL, version 2 or later. + * See the COPYING file in the top-level directory. + */ + +#include "qemu/osdep.h" +#include "qom/object_interfaces.h" +#include "qapi/error.h" +#include "sysemu/event-loop-base.h" + +typedef struct { + const char *name; + ptrdiff_t offset; /* field's byte offset in EventLoopBase struct */ +} EventLoopBaseParamInfo; + +static EventLoopBaseParamInfo aio_max_batch_info = { + "aio-max-batch", offsetof(EventLoopBase, aio_max_batch), +}; + +static void event_loop_base_get_param(Object *obj, Visitor *v, + const char *name, void *opaque, Error **errp) +{ + EventLoopBase *event_loop_base = EVENT_LOOP_BASE(obj); + EventLoopBaseParamInfo *info = opaque; + int64_t *field = (void *)event_loop_base + info->offset; + + visit_type_int64(v, name, field, errp); +} + +static void event_loop_base_set_param(Object *obj, Visitor *v, + const char *name, void *opaque, Error **errp) +{ + EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(obj); + EventLoopBase *base = EVENT_LOOP_BASE(obj); + EventLoopBaseParamInfo *info = opaque; + int64_t *field = (void *)base + info->offset; + int64_t value; + + if (!visit_type_int64(v, name, &value, errp)) { + return; + } + + if (value < 0) { + error_setg(errp, "%s value must be in range [0, %" PRId64 "]", + info->name, INT64_MAX); + return; + } + + *field = value; + + if (bc->update_params) { + bc->update_params(base, errp); + } + + return; +} + +static void event_loop_base_complete(UserCreatable *uc, Error **errp) +{ + EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(uc); + EventLoopBase *base = EVENT_LOOP_BASE(uc); + + if (bc->init) { + bc->init(base, errp); + } +} + +static void event_loop_base_class_init(ObjectClass *klass, void *class_data) +{ + UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass); + ucc->complete = event_loop_base_complete; + + object_class_property_add(klass, "aio-max-batch", "int", + event_loop_base_get_param, + event_loop_base_set_param, + NULL, &aio_max_batch_info); +} + +static const TypeInfo event_loop_base_info = { + .name = TYPE_EVENT_LOOP_BASE, + .parent = TYPE_OBJECT, + .instance_size = sizeof(EventLoopBase), + .class_size = sizeof(EventLoopBaseClass), + .class_init = event_loop_base_class_init, + .abstract = true, + .interfaces = (InterfaceInfo[]) { + { TYPE_USER_CREATABLE }, + { } + } +}; + +static void register_types(void) +{ + type_register_static(&event_loop_base_info); +} +type_init(register_types); -- cgit v1.1 From 70ac26b9e5ca8374bb3ef3f30b871726673c9f27 Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne Date: Mon, 25 Apr 2022 09:57:22 +0200 Subject: util/main-loop: Introduce the main loop into QOM 'event-loop-base' provides basic property handling for all 'AioContext' based event loops. So let's define a new 'MainLoopClass' that inherits from it. This will permit tweaking the main loop's properties through qapi as well as through the command line using the '-object' keyword[1]. Only one instance of 'MainLoopClass' might be created at any time. 'EventLoopBaseClass' learns a new callback, 'can_be_deleted()' so as to mark 'MainLoop' as non-deletable. [1] For example: -object main-loop,id=main-loop,aio-max-batch= Signed-off-by: Nicolas Saenz Julienne Reviewed-by: Stefan Hajnoczi Acked-by: Markus Armbruster Message-id: 20220425075723.20019-3-nsaenzju@redhat.com Signed-off-by: Stefan Hajnoczi --- event-loop-base.c | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'event-loop-base.c') diff --git a/event-loop-base.c b/event-loop-base.c index a924c73..e7f99a6 100644 --- a/event-loop-base.c +++ b/event-loop-base.c @@ -73,10 +73,23 @@ static void event_loop_base_complete(UserCreatable *uc, Error **errp) } } +static bool event_loop_base_can_be_deleted(UserCreatable *uc) +{ + EventLoopBaseClass *bc = EVENT_LOOP_BASE_GET_CLASS(uc); + EventLoopBase *backend = EVENT_LOOP_BASE(uc); + + if (bc->can_be_deleted) { + return bc->can_be_deleted(backend); + } + + return true; +} + static void event_loop_base_class_init(ObjectClass *klass, void *class_data) { UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass); ucc->complete = event_loop_base_complete; + ucc->can_be_deleted = event_loop_base_can_be_deleted; object_class_property_add(klass, "aio-max-batch", "int", event_loop_base_get_param, -- cgit v1.1 From 71ad4713cc1d7fca24388b828ef31ae6cb38a31c Mon Sep 17 00:00:00 2001 From: Nicolas Saenz Julienne Date: Mon, 25 Apr 2022 09:57:23 +0200 Subject: 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 Reviewed-by: Stefan Hajnoczi Acked-by: Markus Armbruster Message-id: 20220425075723.20019-4-nsaenzju@redhat.com Signed-off-by: Stefan Hajnoczi --- event-loop-base.c | 23 +++++++++++++++++++++++ 1 file changed, 23 insertions(+) (limited to 'event-loop-base.c') diff --git a/event-loop-base.c b/event-loop-base.c index e7f99a6..d5be4dc 100644 --- a/event-loop-base.c +++ b/event-loop-base.c @@ -14,6 +14,7 @@ #include "qemu/osdep.h" #include "qom/object_interfaces.h" #include "qapi/error.h" +#include "block/thread-pool.h" #include "sysemu/event-loop-base.h" typedef struct { @@ -21,9 +22,22 @@ typedef struct { ptrdiff_t offset; /* field's byte offset in EventLoopBase struct */ } EventLoopBaseParamInfo; +static void event_loop_base_instance_init(Object *obj) +{ + EventLoopBase *base = EVENT_LOOP_BASE(obj); + + base->thread_pool_max = THREAD_POOL_MAX_THREADS_DEFAULT; +} + static EventLoopBaseParamInfo aio_max_batch_info = { "aio-max-batch", offsetof(EventLoopBase, aio_max_batch), }; +static EventLoopBaseParamInfo thread_pool_min_info = { + "thread-pool-min", offsetof(EventLoopBase, thread_pool_min), +}; +static EventLoopBaseParamInfo thread_pool_max_info = { + "thread-pool-max", offsetof(EventLoopBase, thread_pool_max), +}; static void event_loop_base_get_param(Object *obj, Visitor *v, const char *name, void *opaque, Error **errp) @@ -95,12 +109,21 @@ static void event_loop_base_class_init(ObjectClass *klass, void *class_data) event_loop_base_get_param, event_loop_base_set_param, NULL, &aio_max_batch_info); + object_class_property_add(klass, "thread-pool-min", "int", + event_loop_base_get_param, + event_loop_base_set_param, + NULL, &thread_pool_min_info); + object_class_property_add(klass, "thread-pool-max", "int", + event_loop_base_get_param, + event_loop_base_set_param, + NULL, &thread_pool_max_info); } static const TypeInfo event_loop_base_info = { .name = TYPE_EVENT_LOOP_BASE, .parent = TYPE_OBJECT, .instance_size = sizeof(EventLoopBase), + .instance_init = event_loop_base_instance_init, .class_size = sizeof(EventLoopBaseClass), .class_init = event_loop_base_class_init, .abstract = true, -- cgit v1.1