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SubjectRe: [ckrm-tech] [PATCH 5/13] BC: user interface (syscalls)
Pavel Emelianov wrote:
> Balbir Singh wrote:
>>> +
>>> +asmlinkage long sys_set_bcid(bcid_t id)
>>> +{
>>> + int error;
>>> + struct beancounter *bc;
>>> + struct task_beancounter *task_bc;
>>> +
>>> + task_bc = &current->task_bc;
>> I was playing around with the bc patches and found that to make
>> use of bc's, I had to actually call set_bcid() and then exec() a
>> task/shell so that the id would stick around. Would you consider
> That sounds very strange as sys_set_bcid() actually changes current's
> exec_bc.
> One note is about mm's bc - mm obtains new bc only after fork or exec -
> that's
> true. But kmemsize starts charging right after the sys_set_bcid.

I was playing around only with kmemsize. I think the reason for my observation
is this

bash --> (my utility) --> set_bcid()

Since bash spawns my utility in a separate process, it creates and assigns
a bean counter to it and then my utility exits. Unless it spawns/exec()'s a
new shell, the beancounter is freed when the task exits (my utility).

>> changing sys_set_bcid to sys_set_task_bcid() or adding a new
>> system call sys_set_task_bcid()? We could pass the pid that we
>> intend to associate with the new id. This also means we'll need
>> locking around to protect task->task_bc.


Balbir Singh,
Linux Technology Center,
IBM Software Labs
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