path: root/block
diff options
authorVivek Goyal <vgoyal@redhat.com>2010-11-15 19:37:36 +0100
committerJens Axboe <jaxboe@fusionio.com>2010-11-15 19:37:36 +0100
commitbdc85df7a8417b9893443ff5520804699416b6f3 (patch)
tree7d1158ff87d327934c0c3b0d5ec9b02ed4811de6 /block
parent0143832cc96d0bf78486297aad5c8fb2c2ead02a (diff)
blk-cgroup: Allow creation of hierarchical cgroups
o Allow hierarchical cgroup creation for blkio controller o Currently we disallow it as both the io controller policies (throttling as well as proportion bandwidth) do not support hierarhical accounting and control. But the flip side is that blkio controller can not be used with libvirt as libvirt creates a cgroup hierarchy deeper than 1 level. <top-level-cgroup-dir>/<controller>/libvirt/qemu/<virtual-machine-groups> o So this patch will allow creation of cgroup hierarhcy but at the backend everything will be treated as flat. So if somebody created a an hierarchy like as follows. root / \ test1 test2 | test3 CFQ and throttling will practically treat all groups at same level. pivot / | \ \ root test1 test2 test3 o Once we have actual support for hierarchical accounting and control then we can introduce another cgroup tunable file "blkio.use_hierarchy" which will be 0 by default but if user wants to enforce hierarhical control then it can be set to 1. This way there should not be any ABI problems down the line. o The only not so pretty part is introduction of extra file "use_hierarchy" down the line. Kame-san had mentioned that hierarhical accounting is expensive in memory controller hence they keep it off by default. I suspect same will be the case for IO controller also as for each IO completion we shall have to account IO through hierarchy up to the root. if yes, then it probably is not a very bad idea to introduce this extra file so that it will be used only when somebody needs it and some people might enable hierarchy only in part of the hierarchy. o This is how basically memory controller also uses "use_hierarhcy" and they also allowed creation of hierarchies when actual backend support was not available. Signed-off-by: Vivek Goyal <vgoyal@redhat.com> Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com> Reviewed-by: Gui Jianfeng <guijianfeng@cn.fujitsu.com> Reviewed-by: Ciju Rajan K <ciju@linux.vnet.ibm.com> Tested-by: Ciju Rajan K <ciju@linux.vnet.ibm.com> Signed-off-by: Jens Axboe <jaxboe@fusionio.com>
Diffstat (limited to 'block')
1 files changed, 0 insertions, 4 deletions
diff --git a/block/blk-cgroup.c b/block/blk-cgroup.c
index b1febd0f6d2..455768a3eb9 100644
--- a/block/blk-cgroup.c
+++ b/block/blk-cgroup.c
@@ -1452,10 +1452,6 @@ blkiocg_create(struct cgroup_subsys *subsys, struct cgroup *cgroup)
goto done;
- /* Currently we do not support hierarchy deeper than two level (0,1) */
- if (parent != cgroup->top_cgroup)
- return ERR_PTR(-EPERM);
blkcg = kzalloc(sizeof(*blkcg), GFP_KERNEL);
if (!blkcg)
return ERR_PTR(-ENOMEM);