lkml.org 
[lkml]   [2008]   [Mar]   [27]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC][2/3] Account and control virtual address space allocations (v2)
Pavel Emelyanov wrote:
> Balbir Singh wrote:
>> Changelog v2
>> ------------
>> Change the accounting to what is already present in the kernel. Split
>> the address space accounting into mem_cgroup_charge_as and
>> mem_cgroup_uncharge_as. At the time of VM expansion, call
>> mem_cgroup_cannot_expand_as to check if the new allocation will push
>> us over the limit
>>
>> This patch implements accounting and control of virtual address space.
>> Accounting is done when the virtual address space of any task/mm_struct
>> belonging to the cgroup is incremented or decremented. This patch
>> fails the expansion if the cgroup goes over its limit.
>>
>> TODOs
>>
>> 1. Only when CONFIG_MMU is enabled, is the virtual address space control
>> enabled. Should we do this for nommu cases as well? My suspicion is
>> that we don't have to.
>>
>> Signed-off-by: Balbir Singh <balbir@linux.vnet.ibm.com>
>> ---
>>
>> arch/ia64/kernel/perfmon.c | 2 +
>> arch/x86/kernel/ptrace.c | 7 +++
>> fs/exec.c | 2 +
>> include/linux/memcontrol.h | 26 +++++++++++++
>> include/linux/res_counter.h | 19 ++++++++--
>> init/Kconfig | 2 -
>> kernel/fork.c | 17 +++++++--
>> mm/memcontrol.c | 83 ++++++++++++++++++++++++++++++++++++++++++++
>> mm/mmap.c | 11 +++++
>> mm/mremap.c | 2 +
>> 10 files changed, 163 insertions(+), 8 deletions(-)
>>
>> diff -puN mm/memcontrol.c~memory-controller-virtual-address-space-accounting-and-control mm/memcontrol.c
>> --- linux-2.6.25-rc5/mm/memcontrol.c~memory-controller-virtual-address-space-accounting-and-control 2008-03-26 16:27:59.000000000 +0530
>> +++ linux-2.6.25-rc5-balbir/mm/memcontrol.c 2008-03-27 00:18:16.000000000 +0530
>> @@ -526,6 +526,76 @@ unsigned long mem_cgroup_isolate_pages(u
>> return nr_taken;
>> }
>>
>> +#ifdef CONFIG_CGROUP_MEM_RES_CTLR_AS
>> +/*
>> + * Charge the address space usage for cgroup. This routine is most
>> + * likely to be called from places that expand the total_vm of a mm_struct.
>> + */
>> +void mem_cgroup_charge_as(struct mm_struct *mm, long nr_pages)
>> +{
>> + struct mem_cgroup *mem;
>> +
>> + if (mem_cgroup_subsys.disabled)
>> + return;
>> +
>> + rcu_read_lock();
>> + mem = rcu_dereference(mm->mem_cgroup);
>> + css_get(&mem->css);
>> + rcu_read_unlock();
>> +
>> + res_counter_charge(&mem->as_res, (nr_pages * PAGE_SIZE));
>> + css_put(&mem->css);
>
> Why don't you check whether the counter is charged? This is
> bad for two reasons:
> 1. you allow for some growth above the limit (e.g. in expand_stack)

I was doing that earlier and then decided to keep the virtual address space code
in sync with the RLIMIT_AS checking code in the kernel. If you see the flow, it
closely resembles what we do with mm->total_vm and may_expand_vm().
expand_stack() in turn calls acct_stack_growth() which calls may_expand_vm()

> 2. you will undercharge it in the future when uncharging the
> vme, whose charge was failed and thus unaccounted.

Hmmm... This should ideally never happen, since we do a may_expand_vm() before
expanding the VM and in our case the virtual address space usage. I've not seen
it during my runs either. But it is something to keep in mind.

--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL


\
 
 \ /
  Last update: 2008-03-27 09:09    [W:0.129 / U:0.080 seconds]
©2003-2011 Jasper Spaans. Advertise on this site