Re: [PATCH -mm] mm: fine-grained dirty_ratio_pcm and dirty_background_ratio_pcm (v2)

[Andrew Morton <akpm@linux-foundation.org>]

On Mon, 10 Nov 2008 21:58:28 +0100
Andrea Righi <righi.andrea@gmail.com> wrote:

> The current granularity of 5% of dirtyable memory for dirty pages writeback is
> too coarse for large memory machines and this will get worse as
> memory-size/disk-speed ratio continues to increase.
> 
> These large writebacks can be unpleasant for desktop or latency-sensitive
> environments, where the time to complete each writeback can be perceived as a
> lack of responsiveness by the whole system.
> 
> Following there's a similar solution as discussed in [1], but a little
> bit simplified in order to provide the same functionality (in particular
> to avoid backward compatibility problems) and reduce the amount of code
> needed to implement an in-kernel parser to handle percentages with
> decimals digits.
> 
> The kernel provides the following parameters:
>  - dirty_ratio, dirty_background_ratio in percentage (1 ... 100)
>  - dirty_ratio_pcm, dirty_background_ratio_pcm in units of percent mille (1 ... 100,000)

hm, so how long until dirty_ratio_pcm becomes too coarse...

What happened to the idea of specifying these in units of kilobytes?

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