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

[Michael Rubin]

Currently the problme 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.

Any feedback?

mrubin

On Fri, Sep 12, 2008 at 4:10 PM, Andrew Morton
<akpm at linux-foundation.org> wrote:
> On Sat, 13 Sep 2008 01:04:35 +0200
> Andrea Righi <righi.andrea at gmail.com> wrote:
>
>> BTW why not use a simple dirty-ratio-in-bytes?
>
> s/ratio/amount/  ;)
>
> No particular reason - I haven't really thought about it frankly.
>
> A "ratio" might make more sense in a containerised setup, particularly
> if the container can be resized on the fly.
>
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