[Qemu-devel] Is it possible to retrieve pre-process information in QEMU?

[Qemu-devel] Is it possible to retrieve pre-process information in QEMU?

[陳韋任]

Hi all,

  I would like to know if I can retrieve pre-process information in QEMU
system mode. For example, I want to know each process's page fault ratio.
Is there a way to do that?

  Thanks.

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj

Re: [Qemu-devel] Is it possible to retrieve pre-process information in QEMU?

[Mulyadi Santosa]

Hi...

On Thu, May 17, 2012 at 10:09 AM, 陳韋任 <chenwj@iis.sinica.edu.tw> wrote:
> Hi all,
>
>  I would like to know if I can retrieve pre-process information in QEMU
> system mode. For example, I want to know each process's page fault ratio.
> Is there a way to do that?

logically, it's possible, but you need to locate the task_struct of
each processes first. Using GDB, that might be a bit easier but still
not easy.

Why not just monitor it inside the guest? using system tap for example?

-- 
regards,

Mulyadi Santosa
Freelance Linux trainer and consultant

blog: the-hydra.blogspot.com
training: mulyaditraining.blogspot.com

Re: [Qemu-devel] Is it possible to retrieve pre-process information in QEMU?

[陳韋任]

> >  I would like to know if I can retrieve pre-process information in QEMU
> > system mode. For example, I want to know each process's page fault ratio.
> > Is there a way to do that?
> 
> logically, it's possible, but you need to locate the task_struct of
> each processes first. Using GDB, that might be a bit easier but still
> not easy.
> 
> Why not just monitor it inside the guest? using system tap for example?

  O.K., what I did is something like below,

---
void tlb_fill(CPUARMState *env1, target_ulong addr, int is_write, int mmu_idx,
              uintptr_t retaddr)
{
    ret = cpu_arm_handle_mmu_fault(env, addr, is_write, mmu_idx);
    if (unlikely(ret)) {
        page_fault++;   // page fault
    }
    env = saved_env;
}
---

  IIUC, cpu_arm_handle_mmu_fault will lookup guest page table, return 1 if there
is a page fault, that's why I add a counter there. But this way I'll collect a
global static not per-process one. I'll try systemtap latter but not sure it
does the same thing I want to do.

  Any thoughts? :)

Regards,
chenwj

-- 
Wei-Ren Chen (陳韋任)
Computer Systems Lab, Institute of Information Science,
Academia Sinica, Taiwan (R.O.C.)
Tel:886-2-2788-3799 #1667
Homepage: http://people.cs.nctu.edu.tw/~chenwj