Re: [PATCH] swap: cond_resched in swap_cgroup_prepare()

[Yu Zhao]

On Fri, Jun 02, 2017 at 10:18:57AM +0200, Michal Hocko wrote:
> On Thu 01-06-17 12:56:35, Yu Zhao wrote:
> > Saw need_resched() warnings when swapping on large swapfile (TBs)
> > because page allocation in swap_cgroup_prepare() took too long.
> 
> Hmm, but the page allocator makes sure to cond_resched for sleeping
> allocations. I guess what you mean is something different. It is not the
> allocation which took too look but there are too many of them and none
> of them sleeps because there is enough memory and the allocator doesn't
> sleep in that case. Right?
> 
> > We already cond_resched when freeing page in swap_cgroup_swapoff().
> > Do the same for the page allocation.
> > 
> > Signed-off-by: Yu Zhao <yuzhao@xxxxxxxxxx>
> 
> The patch itself makes sense to me, the changelog could see some
> clarification but other than that
> Acked-by: Michal Hocko <mhocko@xxxxxxxx>

Thanks, I'll clarify the problem in the commit message and resend the
patch.