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block: add throttle block filter driver

Browse source 
block/throttle.c uses existing I/O throttle infrastructure inside a
block filter driver. I/O operations are intercepted in the filter's
read/write coroutines, and referred to block/throttle-groups.c

The driver can be used with the syntax
-drive driver=throttle,file.filename=foo.qcow2,throttle-group=bar

which registers the throttle filter node with the ThrottleGroup 'bar'. The
given group must be created beforehand with object-add or -object.

Reviewed-by: Alberto Garcia <berto@igalia.com>
Signed-off-by: Manos Pitsidianakis <el13635@mail.ntua.gr>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Kevin Wolf <kwolf@redhat.com>
This commit is contained in:
Manos Pitsidianakis 2017-08-25 16:20:27 +03:00 • committed by Kevin Wolf
parent 432d889e55
commit d8e7d87ec4
6 changed files with 275 additions and 2 deletions
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15
block/throttle-groups.c
View file

@ -101,6 +101,14 @@ static ThrottleGroup *throttle_group_by_name(const char *name)
return NULL;
}
/* This function reads throttle_groups and must be called under the global
* mutex.
*/
bool throttle_group_exists(const char *name)
{
return throttle_group_by_name(name) != NULL;
}
/* Increments the reference count of a ThrottleGroup given its name.
*
* If no ThrottleGroup is found with the given name a new one is
@ -543,6 +551,11 @@ void throttle_group_unregister_tgm(ThrottleGroupMember *tgm)
ThrottleGroupMember *token;
int i;
if (!ts) {
/* Discard already unregistered tgm */
return;
}
assert(tgm->pending_reqs[0] == 0 && tgm->pending_reqs[1] == 0);
assert(qemu_co_queue_empty(&tgm->throttled_reqs[0]));
assert(qemu_co_queue_empty(&tgm->throttled_reqs[1]));
@ -709,7 +722,7 @@ static void throttle_group_obj_complete(UserCreatable *obj, Error **errp)
assert(tg->name);
/* error if name is duplicate */
if (throttle_group_by_name(tg->name) != NULL) {
if (throttle_group_exists(tg->name)) {
error_setg(errp, "A group with this name already exists");
return;
}