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Date: Wed, 19 Jan 2011 09:20:20 +0800 From: Gui Jianfeng <guijianfeng@...fujitsu.com> To: Vivek Goyal <vgoyal@...hat.com> CC: Jens Axboe <axboe@...nel.dk>, linux kernel mailing list <linux-kernel@...r.kernel.org>, Corrado Zoccolo <czoccolo@...il.com>, Chad Talbott <ctalbott@...gle.com>, Nauman Rafique <nauman@...gle.com>, Divyesh Shah <dpshah@...gle.com>, jmoyer@...hat.com, Shaohua Li <shaohua.li@...el.com> Subject: Re: [PATCH 6/6 v3] blkio-cgroup: Document for blkio.use_hierarchy interface Vivek Goyal wrote: > On Mon, Dec 27, 2010 at 04:51:20PM +0800, Gui Jianfeng wrote: >> Document for blkio.use_hierarchy interface >> >> Signed-off-by: Gui Jianfeng <guijianfeng@...fujitsu.com> >> --- >> Documentation/cgroups/blkio-controller.txt | 70 ++++++++++++++++++++-------- >> 1 files changed, 51 insertions(+), 19 deletions(-) >> >> diff --git a/Documentation/cgroups/blkio-controller.txt b/Documentation/cgroups/blkio-controller.txt >> index 4ed7b5c..bd01d6c 100644 >> --- a/Documentation/cgroups/blkio-controller.txt >> +++ b/Documentation/cgroups/blkio-controller.txt >> @@ -91,30 +91,51 @@ Throttling/Upper Limit policy >> >> Hierarchical Cgroups >> ==================== >> -- Currently none of the IO control policy supports hierarhical groups. But >> - cgroup interface does allow creation of hierarhical cgroups and internally >> - IO policies treat them as flat hierarchy. >> +- Cgroup interface allows creation of hierarchical cgroups. Currently, >> + internally IO policies are able to treat them as flat hierarchy or >> + hierarchical hierarchy. > > Gui, now we have 2 IO policies. Throttling policy still supports only flat > mode. Can you please make it clear here that CFQ will support both flat > and hierarhical mode while throttling supports only flat mode as of today. > >> Both hierarchical bandwidth division and flat >> + bandwidth division are supported. "blkio.use_hierarchy" can be used to >> + switch between flat mode and hierarchical mode. >> >> - So this patch will allow creation of cgroup hierarhcy but at the backend >> - everything will be treated as flat. So if somebody created a hierarchy like >> - as follows. >> + Consider the following CGroup hierarchy: >> >> - root >> - / \ >> - test1 test2 >> - | >> - test3 >> + Root >> + / | \ >> + Grp1 Grp2 tsk1 >> + / \ >> + Grp3 tsk2 >> >> - CFQ and throttling will practically treat all groups at same level. >> + If blkio.use_hierarchy is disabled in all CGroups, CFQ will practically treat all groups >> + at the same level. >> >> - pivot >> - / | \ \ >> - root test1 test2 test3 >> + Pivot tree >> + / | | \ >> + Root Grp1 Grp2 Grp3 >> + / | >> + tsk1 tsk2 >> >> - Down the line we can implement hierarchical accounting/control support >> - and also introduce a new cgroup file "use_hierarchy" which will control >> - whether cgroup hierarchy is viewed as flat or hierarchical by the policy.. >> - This is how memory controller also has implemented the things. >> + If blkio.use_hierarchy is enabled in Grp1 and Grp3, CFQ will treat groups and tasks as the > > I would think that before this example, we can give one simpler example > where use_hierarhcy=1 in root cgroup and that would/should lead to all > children group under root having use_hierarchy=1 set automatically and > will look as follows. > > Pivot tree > | > root > / | | > tsk1 G1 G2 > / \ > grp3 tsk2 > > After this now you can give more complicated example as below where > use_hierarchy=1 is only set for sub branch of tree and not the whole > tree. Sure. > >> + same view in CGroup hierarchy, it looks as follows. >> + >> + >> + Pivot tree >> + / | \ >> + Root Grp1 Grp2 >> + / / \ >> + tsk1 Grp3 tsk2 >> + >> + Root, Grp1 and Grp2 are treated at the same level under Pivot tree. tsk1 stays under Root. >> + Grp3 and tsk2 are treated at the same level under Grp1. Below is the mapping between >> + task io priority and io weight: >> + >> + prio 0 1 2 3 4 5 6 7 >> + weight 1000 868 740 612 484 356 228 100 >> + >> + Note1: Regardless of the use_hierarchy setting in Root group, Root group is always put onto >> + Pivot tree. >> + >> + Note2: Currently, "blkio.use_hierarchy" only effects proportional bandwidth division. For >> + Throttling logic, it still continue to treat everything as flat. >> > > Ok, I see you mentioned throttling flat mode here. I guess it is better > to clarify it in the beginning itself. Ok Thanks, Gui > >> Various user visible config options >> =================================== >> @@ -169,6 +190,17 @@ Proportional weight policy files >> dev weight >> 8:16 300 >> >> +- blkio.use_hierarchy >> + - Switch between hierarchical mode and flat mode as stated above. >> + blkio.use_hierarchy == 1 means hierarchical mode is enabled. >> + blkio.use_hierarchy == 0 means flat mode is enabled. >> + You can set this interface only if there isn't any child CGroup under >> + this CGroup. If one CGroup's blkio.use_hierarchy is set, the created >> + children will inherit it. it's not allowed to unset it in children. >> + The default mode in Root CGroup is flat. >> + blkio.use_hierarchy only works for proportional bandwidth division >> + as of today and doesn't have any effect on throttling logic. >> + > > This is good. Makes use_hierarchy behavior for children and subtree very > clear. > >> - blkio.time >> - disk time allocated to cgroup per device in milliseconds. First >> two fields specify the major and minor number of the device and >> -- >> 1.6.5.2 >> >> >> >> >> >> > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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