[Qemu-devel] [RFC V2 2/8] throttle: Add throttle group infrastructure

[Benoît Canet]

The throttle_group_incref increment the refcount of a throttle group given it's
name and return the associated throttle state.

The throttle_group_unref is the mirror function for cleaning up.

Signed-off-by: Benoit Canet <address@hidden>
---
 block/Makefile.objs             |   1 +
 block/throttle-groups.c         | 212 ++++++++++++++++++++++++++++++++++++++++
 include/block/block_int.h       |   1 +
 include/block/throttle-groups.h |  45 +++++++++
 4 files changed, 259 insertions(+)
 create mode 100644 block/throttle-groups.c
 create mode 100644 include/block/throttle-groups.h

diff --git a/block/Makefile.objs b/block/Makefile.objs
index fd88c03..72ce2d3 100644
--- a/block/Makefile.objs
+++ b/block/Makefile.objs
@@ -9,6 +9,7 @@ block-obj-y += snapshot.o qapi.o
 block-obj-$(CONFIG_WIN32) += raw-win32.o win32-aio.o
 block-obj-$(CONFIG_POSIX) += raw-posix.o
 block-obj-$(CONFIG_LINUX_AIO) += linux-aio.o
+block-obj-y += throttle-groups.o
 
 ifeq ($(CONFIG_POSIX),y)
 block-obj-y += nbd.o nbd-client.o sheepdog.o
diff --git a/block/throttle-groups.c b/block/throttle-groups.c
new file mode 100644
index 0000000..ea5baca
--- /dev/null
+++ b/block/throttle-groups.c
@@ -0,0 +1,212 @@
+/*
+ * QEMU block throttling group infrastructure
+ *
+ * Copyright (C) Nodalink, EURL. 2014
+ *
+ * Author:
+ *   Benoît Canet <address@hidden>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 or
+ * (at your option) version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#include "block/throttle-groups.h"
+#include "qemu/queue.h"
+#include "qemu/thread.h"
+
+typedef struct ThrottleGroup {
+    char name[32];
+    ThrottleState ts;
+    uint64_t refcount;
+    QTAILQ_ENTRY(ThrottleGroup) list;
+    QLIST_HEAD(, BlockDriverState) head;
+    BlockDriverState *tokens[2]; /* current round-robin tokens */
+    QemuMutex lock; /* Used to synchronize all elements belonging to a group */
+} ThrottleGroup;
+
+static QTAILQ_HEAD(, ThrottleGroup) throttle_groups =
+    QTAILQ_HEAD_INITIALIZER(throttle_groups);
+
+/* increments a ThrottleGroup reference count given it's name
+ *
+ * If no ThrottleGroup is found with the given name a new one is created.
+ *
+ * @name: the name of the ThrottleGroup
+ * @ret:  the ThrottleGroup's ThrottleState address
+ */
+ThrottleState *throttle_group_incref(const char *name)
+{
+    ThrottleGroup *tg;
+
+    /* return the correct ThrottleState if a group with this name exists */
+    QTAILQ_FOREACH(tg, &throttle_groups, list) {
+        /* group not found -> continue */
+        if (strcmp(name, tg->name)) {
+            continue;
+        }
+        /* group found -> increment it's refcount and return ThrottleState */
+        tg->refcount++;
+        return &tg->ts;
+    }
+
+    /* throttle group not found -> prepare new entry */
+    tg = g_new0(ThrottleGroup, 1);
+    pstrcpy(tg->name, sizeof(tg->name), name);
+    qemu_mutex_init(&tg->lock);
+    throttle_init(&tg->ts);
+    QLIST_INIT(&tg->head);
+    tg->refcount = 1;
+
+    /* insert new entry in the list */
+    QTAILQ_INSERT_TAIL(&throttle_groups, tg, list);
+
+    /* return newly allocated ThrottleState */
+    return &tg->ts;
+}
+
+/* decrement a ThrottleGroup given it's ThrottleState address
+ *
+ * When the refcount reach zero the ThrottleGroup is destroyed
+ *
+ * @ts:  The ThrottleState address belonging to the ThrottleGroup to unref
+ * @ret: true on success else false
+ */
+bool throttle_group_unref(ThrottleState *ts)
+{
+    ThrottleGroup *tg;
+    bool found = false;
+
+    /* Find the ThrottleGroup of the given ThrottleState */
+    QTAILQ_FOREACH(tg, &throttle_groups, list) {
+        /* correct group found stop iterating */
+        if (&tg->ts == ts) {
+            qemu_mutex_lock(&tg->lock);
+            found = true;
+            break;
+        }
+    }
+
+    /* If the ThrottleState was not found something is seriously broken */
+    if (!found) {
+        return false;
+    }
+
+    tg->refcount--;
+
+    /* If ThrottleGroup is used keep it. */
+    if (tg->refcount) {
+        qemu_mutex_unlock(&tg->lock);
+        return true;
+    }
+
+    /* Else destroy it */
+    QTAILQ_REMOVE(&throttle_groups, tg, list);
+    qemu_mutex_unlock(&tg->lock);
+    qemu_mutex_destroy(&tg->lock);
+    g_free(tg);
+    return true;
+}
+
+/* Compare a name with a given ThrottleState group name
+ *
+ * @ts:   the throttle state whose group we are inspecting
+ * @name: the name to compare
+ * @ret:  true if names are equal else false
+ */
+bool throttle_group_compare(ThrottleState *ts, const char *name)
+{
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+
+    if (!name) {
+        return false;
+    }
+
+    return !strcmp(name, tg->name);
+}
+
+/* Register a BlockDriverState in the doubly linked list
+ *
+ * @ts: the ThrottleState the code is working on
+ * @bs: the BlockDriverState to insert
+ */
+void throttle_group_register_bs(ThrottleState *ts, BlockDriverState *bs)
+{
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    QLIST_INSERT_HEAD(&tg->head, bs, round_robin);
+}
+
+/* Return the next BlockDriverState in the round-robin sequence
+ *
+ * This takes care of simulating a circular list
+ *
+ * @bs:  the input current BlockDriverState
+ * @ret: the next BlockDriverState in the sequence
+ */
+BlockDriverState *throttle_group_next_bs(BlockDriverState *bs)
+{
+    ThrottleState *ts = &bs->throttle_state;
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    BlockDriverState *next = QLIST_NEXT(bs, round_robin);
+
+    if (!next) {
+        return QLIST_FIRST(&tg->head);
+    }
+
+    return next;
+}
+
+/* Used to set a token BlockDriverState into a ThrottleState's ThrottleGroup
+ *
+ * @ts:       the ThrottleState the code is working on
+ * @token:    the token BlockDriverState to set
+ * @is_write: true if we are talking about write operations else false
+ */
+void throttle_group_set_token(ThrottleState *ts,
+                              BlockDriverState *token,
+                              bool is_write)
+{
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    tg->tokens[is_write] = token;
+}
+
+/* Used to get the token BlockDriverState of a ThrottleState's ThrottleGroup
+ *
+ * @ts:  the ThrottleState the code is working on
+ * @ret: the token BlockDriverState that is retrieved
+ * @is_write: true if we are talking about write operations else false
+ */
+BlockDriverState *throttle_group_token(ThrottleState *ts, bool is_write)
+{
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    return tg->tokens[is_write];
+}
+
+/* Used to lock a ThrottleState's ThrottleGroup
+ *
+ * @ts:     the ThrottleState the code is working on
+ */
+void throttle_group_lock(ThrottleState *ts)
+{
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    qemu_mutex_lock(&tg->lock);
+}
+
+/* Used to unlock a ThrottleState's ThrottleGroup
+ *
+ * @ts:  the ThrottleState the code is working on
+ */
+void throttle_group_unlock(ThrottleState *ts)
+{
+    ThrottleGroup *tg = container_of(ts, ThrottleGroup, ts);
+    qemu_mutex_unlock(&tg->lock);
+}
diff --git a/include/block/block_int.h b/include/block/block_int.h
index 2a0c146..6066f63 100644
--- a/include/block/block_int.h
+++ b/include/block/block_int.h
@@ -339,6 +339,7 @@ struct BlockDriverState {
     ThrottleTimers throttle_timers; 
     CoQueue      throttled_reqs[2];
     bool         io_limits_enabled;
+    QLIST_ENTRY(BlockDriverState) round_robin;
 
     /* I/O stats (display with "info blockstats"). */
     uint64_t nr_bytes[BDRV_MAX_IOTYPE];
diff --git a/include/block/throttle-groups.h b/include/block/throttle-groups.h
new file mode 100644
index 0000000..d000067
--- /dev/null
+++ b/include/block/throttle-groups.h
@@ -0,0 +1,45 @@
+/*
+ * QEMU block throttling group infrastructure
+ *
+ * Copyright (C) Nodalink, EURL. 2014
+ *
+ * Author:
+ *   Benoît Canet <address@hidden>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License as
+ * published by the Free Software Foundation; either version 2 or
+ * (at your option) version 3 of the License.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, see <http://www.gnu.org/licenses/>.
+ */
+
+#ifndef THROTTLE_GROUPS_H
+#define THROTTLE_GROUPS_H
+
+#include "qemu/throttle.h"
+#include "block/block_int.h"
+
+ThrottleState *throttle_group_incref(const char *name);
+bool throttle_group_unref(ThrottleState *ts);
+
+bool throttle_group_compare(ThrottleState *ts, const char *name);
+
+void throttle_group_register_bs(ThrottleState *ts, BlockDriverState *bs);
+BlockDriverState *throttle_group_next_bs(BlockDriverState *bs);
+
+void throttle_group_set_token(ThrottleState *ts,
+                              BlockDriverState *token,
+                              bool is_write);
+BlockDriverState *throttle_group_token(ThrottleState *ts, bool is_write);
+
+void throttle_group_lock(ThrottleState *ts);
+void throttle_group_unlock(ThrottleState *ts);
+
+#endif
-- 
2.1.0.rc1