Re: [RFC] [PATCH -mm 0/2] memcg: per cgroup dirty_ratio

[KOSAKI Motohiro]

> Currently the problem we are hitting is that we cannot specify pdflush
> to have background limits less than 1% of memory. I am currently
> finishing up a patch right now that adds a dirty_ratio_millis
> interface.  I hope to submit the patch to LKML by the end of the week.
> 
> The idea is that we don't want to break backwards compatibility and we
> also don't want to have two conflicting knobs in the sysctl or
> /proc/sys/vm/ space. I thought adding a new knob for those who want to
> specify finer grained functionality was a compromise. So the patch has
> a vm_dirty_ratio and a vm_dirty_ratio_millis interface. The first to
> specify 0-100% and the second to specify .0 to .999%.
> 
> So to represent 0.125% of RAM we set
> vm_dirty_ratio = 0
> vm_dirty_ratio_millis = 125
> 
> The same for the background_ratio.

Why vm_dirty_ratio = 0.125 is wrong?
it is hardly for parser maker, but it have nicer user experience.

> 
> I would also prefer using a bytes interface but I am not sure how to
> offer that without  either removing the legacy interface of the ratios
> or by offering a concurrent interface that might be confusing such as
> when users are looking at the old one and not aware of a new one.
> 
> Any feedback?

Sure.
We don't have any motivation of its interface change.



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