Messages in this thread | | | Date | Mon, 17 Mar 2008 20:09:34 +0530 | From | Balbir Singh <> | Subject | Re: [RFC][2/3] Account and control virtual address space allocations |
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Pavel Emelyanov wrote: > Balbir Singh wrote: >> Pavel Emelyanov wrote: >>> Balbir Singh wrote: >>>> Pavel Emelyanov wrote: >>>>> [snip] >>>>> >>>>>> +int mem_cgroup_update_as(struct mm_struct *mm, long nr_pages) >>>>>> +{ >>>>>> + int ret = 0; >>>>>> + struct mem_cgroup *mem; >>>>>> + if (mem_cgroup_subsys.disabled) >>>>>> + return ret; >>>>>> + >>>>>> + rcu_read_lock(); >>>>>> + mem = rcu_dereference(mm->mem_cgroup); >>>>>> + css_get(&mem->css); >>>>>> + rcu_read_unlock(); >>>>>> + >>>>>> + if (nr_pages > 0) { >>>>>> + if (res_counter_charge(&mem->as_res, (nr_pages * PAGE_SIZE))) >>>>>> + ret = 1; >>>>>> + } else >>>>>> + res_counter_uncharge(&mem->as_res, (-nr_pages * PAGE_SIZE)); >>>>> No, please, no. Let's make two calls - mem_cgroup_charge_as and mem_cgroup_uncharge_as. >>>>> >>>>> [snip] >>>>> >>>> Yes, sure :) >>> Thanks :) >>> >>>>>> @@ -1117,6 +1117,9 @@ munmap_back: >>>>>> } >>>>>> } >>>>>> >>>>>> + if (mem_cgroup_update_as(mm, len >> PAGE_SHIFT)) >>>>>> + return -ENOMEM; >>>>>> + >>>>> Why not use existintg cap_vm_enough_memory and co? >>>>> >>>> I thought about it and almost used may_expand_vm(), but there is a slight catch >>>> there. With cap_vm_enough_memory() or security_vm_enough_memory(), they are >>>> called after total_vm has been calculated. In our case we need to keep the >>>> cgroups equivalent of total_vm up to date, and we do this in mem_cgorup_update_as. >>> So? What prevents us from using these hooks? :) >> 1. We need to account total_vm usage of the task anyway. So why have two places, >> one for accounting and second for control? > > We still have two of them even placing hooks in each place manually. > > Besides, putting the mem_cgroup_(un)charge_as() in these vm hooks will > 1. save the number of places to patch > 2. help keeping memcgroup consistent in case someone adds more places > that expand tasks vm (arches, drivers) - in case we have our hooks > celled from inside vm ones, we won't have to patch more. >
I am not sure I understand your proposal. Without manually placing these hooks how do we track
1. When the vm size has increased/decreased 2. In case due to some reason, the call following these hooks fail, how do we undo it, without placing hooks?
>> 2. These hooks are activated for conditionally invoked for vma's with VM_ACCOUNT >> set. > > This is a good point against. But, wrt my previous comment, can we handle > this somehow?
Not sure I understand
-- Warm Regards, Balbir Singh Linux Technology Center IBM, ISTL
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