Messages in this thread | | | Date | Mon, 17 Mar 2008 16:01:01 +0300 | From | Pavel Emelyanov <> | Subject | Re: [RFC][2/3] Account and control virtual address space allocations |
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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.
> 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?
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