Messages in this thread | | | Date | Sun, 02 Nov 2008 17:16:35 +0530 | From | Balbir Singh <> | Subject | Re: [mm] [PATCH 2/4] Memory cgroup resource counters for hierarchy |
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KAMEZAWA Hiroyuki wrote: > On Sun, 02 Nov 2008 11:19:38 +0530 > Balbir Singh <balbir@linux.vnet.ibm.com> wrote: > >> KAMEZAWA Hiroyuki wrote: >>> On Sun, 02 Nov 2008 00:18:37 +0530 >>> Balbir Singh <balbir@linux.vnet.ibm.com> wrote: >>> >>>> Add support for building hierarchies in resource counters. Cgroups allows us >>>> to build a deep hierarchy, but we currently don't link the resource counters >>>> belonging to the memory controller control groups, which are linked in >>>> cgroup hiearchy. This patch provides the infrastructure for resource counters >>>> that have the same hiearchy as their cgroup counter parts. >>>> >>>> These set of patches are based on the resource counter hiearchy patches posted >>>> by Pavel Emelianov. >>>> >>>> NOTE: Building hiearchies is expensive, deeper hierarchies imply charging >>>> the all the way up to the root. It is known that hiearchies are expensive, >>>> so the user needs to be careful and aware of the trade-offs before creating >>>> very deep ones. >>>> >>> ...isn't it better to add "root_lock" to res_counter rather than taking >>> all levels of lock one by one ? >>> >>> spin_lock(&res_counter->hierarchy_root->lock); >>> do all charge/uncharge to hierarchy >>> spin_unlock(&res_counter->hierarchy_root->lock); >>> >>> Hmm ? >>> >> Good thought process, but that affects and adds code complexity for the case >> when hierarchy is enabled/disabled. It is also inefficient, since all charges >> will now contend on root lock, in the current process, it is step by step, the >> contention only occurs on common parts of the hierarchy (root being the best case). >> > > Above code's contention level is not different from "only root no children" case. > Just inside-lock is heavier.
Yes, correct! I think the approach in the patches is better.
-- Balbir
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