On Thu, 11 Nov 2010 14:33:16 -0600 "Steven J. Magnani" <steve@xxxxxxxxxxxxxxx> wrote:
> Depending on processor speed, page size, and the amount of memory a process
> is allowed to amass, cleanup of a large VM may freeze the system for many
> seconds. This can result in a watchdog timeout.
hm, that's no good.
> Make sure other tasks receive some service when cleaning up large VMs.
>
> Signed-off-by: Steven J. Magnani <steve@xxxxxxxxxxxxxxx>
> ---
> diff -uprN a/mm/nommu.c b/mm/nommu.c
> --- a/mm/nommu.c 2010-10-21 07:42:23.000000000 -0500
> +++ b/mm/nommu.c 2010-10-21 07:46:50.000000000 -0500
> @@ -1656,6 +1656,7 @@ SYSCALL_DEFINE2(munmap, unsigned long, a
> void exit_mmap(struct mm_struct *mm)
> {
> struct vm_area_struct *vma;
> + unsigned long next_yield = jiffies + HZ;
>
> if (!mm)
> return;
> @@ -1668,6 +1669,11 @@ void exit_mmap(struct mm_struct *mm)
> mm->mmap = vma->vm_next;
> delete_vma_from_mm(vma);
> delete_vma(mm, vma);
> + /* Yield periodically to prevent watchdog timeout */
> + if (time_after(jiffies, next_yield)) {
> + cond_resched();
> + next_yield = jiffies + HZ;
> + }
> }
>
> kleave("");
You might be able to do this a bit more neatly with __ratelimit:
DEFINE_RATELIMIT_STATE(rl, HZ, 1);
...
if (___ratelimit(&rl, NULL))
cond_resched();
but ___ratelimit() isn't really ready for that - it still has (easily
fixed) assumptions that it's being used for printk ratelimiting.
But anyway. cond_resched() is pretty efficient and one second is still
a very long time. I suspect you don't need the ratelimiting at all?
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