From d8682ef60e3a658d776473fee2299015dd5105d7 Mon Sep 17 00:00:00 2001

From: Stefano Garzarella <sgarzare@redhat.com>

Date: Thu, 29 Jul 2021 07:42:31 -0400

Subject: [PATCH 18/39] iothread: add aio-max-batch parameter

RH-Author: Miroslav Rezanina <mrezanin@redhat.com>

RH-MergeRequest: 32: Synchronize with RHEL-AV 8.5 release 27 to RHEL 9

RH-Commit: [10/15] d033b3c8ddd71bae799103832039d6daa6dfad52 (mrezanin/centos-src-qemu-kvm)

RH-Bugzilla: 1957194

RH-Acked-by: Stefano Garzarella <sgarzare@redhat.com>

RH-Acked-by: Kevin Wolf <kwolf@redhat.com>

RH-Acked-by: Igor Mammedov <imammedo@redhat.com>

RH-Acked-by: Andrew Jones <drjones@redhat.com>

The `aio-max-batch` parameter will be propagated to AIO engines

and it will be used to control the maximum number of queued requests.

When there are in queue a number of requests equal to `aio-max-batch`,

the engine invokes the system call to forward the requests to the kernel.

This parameter allows us to control the maximum batch size to reduce

the latency that requests might accumulate while queued in the AIO

engine queue.

If `aio-max-batch` is equal to 0 (default value), the AIO engine will

use its default maximum batch size value.

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

Message-id: 20210721094211.69853-3-sgarzare@redhat.com

Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

(cherry picked from commit 1793ad0247cad35db1ebbc04fbea0446c30a27ca)

Signed-off-by: Stefano Garzarella <sgarzare@redhat.com>

Signed-off-by: Miroslav Rezanina <mrezanin@redhat.com>

---

 include/block/aio.h       | 12 +++++++++

 include/sysemu/iothread.h |  3 +++

 iothread.c                | 55 +++++++++++++++++++++++++++++++++++----

 monitor/hmp-cmds.c        |  2 ++

 qapi/misc.json            |  6 ++++-

 qapi/qom.json             |  7 ++++-

 qemu-options.hx           |  8 ++++--

 util/aio-posix.c          | 12 +++++++++

 util/aio-win32.c          |  5 ++++

 util/async.c              |  2 ++

 10 files changed, 103 insertions(+), 9 deletions(-)

diff --git a/include/block/aio.h b/include/block/aio.h

index 5f342267d5..ea68a139c8 100644

--- a/include/block/aio.h

+++ b/include/block/aio.h

@@ -232,6 +232,9 @@ struct AioContext {

     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

@@ -727,4 +730,13 @@ 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);

+

 #endif

diff --git a/include/sysemu/iothread.h b/include/sysemu/iothread.h

index f177142f16..7f714bd136 100644

--- a/include/sysemu/iothread.h

+++ b/include/sysemu/iothread.h

@@ -37,6 +37,9 @@ struct IOThread {

     int64_t poll_max_ns;

     int64_t poll_grow;

     int64_t poll_shrink;

+

+    /* AioContext AIO engine parameters */

+    int64_t aio_max_batch;

 };

 typedef struct IOThread IOThread;

diff --git a/iothread.c b/iothread.c

index a12de6e455..272be5e146 100644

--- a/iothread.c

+++ b/iothread.c

@@ -159,6 +159,24 @@ static void iothread_init_gcontext(IOThread *iothread)

     iothread->main_loop = g_main_loop_new(iothread->worker_context, TRUE);

 }

+static void iothread_set_aio_context_params(IOThread *iothread, Error **errp)

+{

+    ERRP_GUARD();

+

+    aio_context_set_poll_params(iothread->ctx,

+                                iothread->poll_max_ns,

+                                iothread->poll_grow,

+                                iothread->poll_shrink,

+                                errp);

+    if (*errp) {

+        return;

+    }

+

+    aio_context_set_aio_params(iothread->ctx,

+                               iothread->aio_max_batch,

+                               errp);

+}

+

 static void iothread_complete(UserCreatable *obj, Error **errp)

 {

     Error *local_error = NULL;

@@ -178,11 +196,7 @@ static void iothread_complete(UserCreatable *obj, Error **errp)

      */

     iothread_init_gcontext(iothread);

-    aio_context_set_poll_params(iothread->ctx,

-                                iothread->poll_max_ns,

-                                iothread->poll_grow,

-                                iothread->poll_shrink,

-                                &local_error);

+    iothread_set_aio_context_params(iothread, &local_error);

     if (local_error) {

         error_propagate(errp, local_error);

         aio_context_unref(iothread->ctx);

@@ -219,6 +233,9 @@ static PollParamInfo poll_grow_info = {

 static PollParamInfo poll_shrink_info = {

     "poll-shrink", offsetof(IOThread, poll_shrink),

 };

+static PollParamInfo aio_max_batch_info = {

+    "aio-max-batch", offsetof(IOThread, aio_max_batch),

+};

 static void iothread_get_param(Object *obj, Visitor *v,

         const char *name, void *opaque, Error **errp)

@@ -278,6 +295,29 @@ static void iothread_set_poll_param(Object *obj, Visitor *v,

     }

 }

+static void iothread_get_aio_param(Object *obj, Visitor *v,

+        const char *name, void *opaque, Error **errp)

+{

+

+    iothread_get_param(obj, v, name, opaque, errp);

+}

+

+static void iothread_set_aio_param(Object *obj, Visitor *v,

+        const char *name, void *opaque, Error **errp)

+{

+    IOThread *iothread = IOTHREAD(obj);

+

+    if (!iothread_set_param(obj, v, name, opaque, errp)) {

+        return;

+    }

+

+    if (iothread->ctx) {

+        aio_context_set_aio_params(iothread->ctx,

+                                   iothread->aio_max_batch,

+                                   errp);

+    }

+}

+

 static void iothread_class_init(ObjectClass *klass, void *class_data)

 {

     UserCreatableClass *ucc = USER_CREATABLE_CLASS(klass);

@@ -295,6 +335,10 @@ static void iothread_class_init(ObjectClass *klass, void *class_data)

                               iothread_get_poll_param,

                               iothread_set_poll_param,

                               NULL, &poll_shrink_info);

+    object_class_property_add(klass, "aio-max-batch", "int",

+                              iothread_get_aio_param,

+                              iothread_set_aio_param,

+                              NULL, &aio_max_batch_info);

 }

 static const TypeInfo iothread_info = {

@@ -344,6 +388,7 @@ static int query_one_iothread(Object *object, void *opaque)

     info->poll_max_ns = iothread->poll_max_ns;

     info->poll_grow = iothread->poll_grow;

     info->poll_shrink = iothread->poll_shrink;

+    info->aio_max_batch = iothread->aio_max_batch;

     QAPI_LIST_APPEND(*tail, info);

     return 0;

diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c

index cc15d9b6ee..2905bc1594 100644

--- a/monitor/hmp-cmds.c

+++ b/monitor/hmp-cmds.c

@@ -1889,6 +1889,8 @@ void hmp_info_iothreads(Monitor *mon, const QDict *qdict)

         monitor_printf(mon, "  poll-max-ns=%" PRId64 "\n", value->poll_max_ns);

         monitor_printf(mon, "  poll-grow=%" PRId64 "\n", value->poll_grow);

         monitor_printf(mon, "  poll-shrink=%" PRId64 "\n", value->poll_shrink);

+        monitor_printf(mon, "  aio-max-batch=%" PRId64 "\n",

+                       value->aio_max_batch);

     }

     qapi_free_IOThreadInfoList(info_list);

diff --git a/qapi/misc.json b/qapi/misc.json

index 156f98203e..5c2ca3b556 100644

--- a/qapi/misc.json

+++ b/qapi/misc.json

@@ -86,6 +86,9 @@

 # @poll-shrink: how many ns will be removed from polling time, 0 means that

 #               it's not configured (since 2.9)

 #

+# @aio-max-batch: maximum number of requests in a batch for the AIO engine,

+#                 0 means that the engine will use its default (since 6.1)

+#

 # Since: 2.0

 ##

 { 'struct': 'IOThreadInfo',

@@ -93,7 +96,8 @@

            'thread-id': 'int',

            'poll-max-ns': 'int',

            'poll-grow': 'int',

-           'poll-shrink': 'int' } }

+           'poll-shrink': 'int',

+           'aio-max-batch': 'int' } }

 ##

 # @query-iothreads:

diff --git a/qapi/qom.json b/qapi/qom.json

index cd0e76d564..f361157903 100644

--- a/qapi/qom.json

+++ b/qapi/qom.json

@@ -516,12 +516,17 @@

 #               algorithm detects it is spending too long polling without

 #               encountering events. 0 selects a default behaviour (default: 0)

 #

+# @aio-max-batch: maximum number of requests in a batch for the AIO engine,

+#                 0 means that the engine will use its default

+#                 (default:0, since 6.1)

+#

 # Since: 2.0

 ##

 { 'struct': 'IothreadProperties',

   'data': { '*poll-max-ns': 'int',

             '*poll-grow': 'int',

-            '*poll-shrink': 'int' } }

+            '*poll-shrink': 'int',

+            '*aio-max-batch': 'int' } }

 ##

 # @MemoryBackendProperties:

diff --git a/qemu-options.hx b/qemu-options.hx

index 79ca09feac..d5f1ec27c5 100644

--- a/qemu-options.hx

+++ b/qemu-options.hx

@@ -5185,7 +5185,7 @@ SRST

             CN=laptop.example.com,O=Example Home,L=London,ST=London,C=GB

-    ``-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink``

+    ``-object iothread,id=id,poll-max-ns=poll-max-ns,poll-grow=poll-grow,poll-shrink=poll-shrink,aio-max-batch=aio-max-batch``

         Creates a dedicated event loop thread that devices can be

         assigned to. This is known as an IOThread. By default device

         emulation happens in vCPU threads or the main event loop thread.

@@ -5221,7 +5221,11 @@ SRST

         the polling time when the algorithm detects it is spending too

         long polling without encountering events.

-        The polling parameters can be modified at run-time using the

+        The ``aio-max-batch`` parameter is the maximum number of requests

+        in a batch for the AIO engine, 0 means that the engine will use

+        its default.

+

+        The IOThread parameters can be modified at run-time using the

         ``qom-set`` command (where ``iothread1`` is the IOThread's

         ``id``):

diff --git a/util/aio-posix.c b/util/aio-posix.c

index 30f5354b1e..2b86777e91 100644

--- a/util/aio-posix.c

+++ b/util/aio-posix.c

@@ -716,3 +716,15 @@ void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,

     aio_notify(ctx);

 }

+

+void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch,

+                                Error **errp)

+{

+    /*

+     * No thread synchronization here, it doesn't matter if an incorrect value

+     * is used once.

+     */

+    ctx->aio_max_batch = max_batch;

+

+    aio_notify(ctx);

+}

diff --git a/util/aio-win32.c b/util/aio-win32.c

index 168717b51b..d5b09a1193 100644

--- a/util/aio-win32.c

+++ b/util/aio-win32.c

@@ -440,3 +440,8 @@ void aio_context_set_poll_params(AioContext *ctx, int64_t max_ns,

         error_setg(errp, "AioContext polling is not implemented on Windows");

     }

 }

+

+void aio_context_set_aio_params(AioContext *ctx, int64_t max_batch,

+                                Error **errp)

+{

+}

diff --git a/util/async.c b/util/async.c

index 674dbefb7c..6a9588d86b 100644

--- a/util/async.c

+++ b/util/async.c

@@ -537,6 +537,8 @@ AioContext *aio_context_new(Error **errp)

     ctx->poll_grow = 0;

     ctx->poll_shrink = 0;

+    ctx->aio_max_batch = 0;

+

     return ctx;

 fail:

     g_source_destroy(&ctx->source);

-- 

2.27.0