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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Zan Lynx <zlynx@acm.org>
Subject: Re: RFC: dirty_ratio back to 40%
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       LKML <linux-kernel@vger.kernel.org>, linux-mm <linux-mm@kvack.org>,
       Nick Piggin <npiggin@suse.de>, Jan Kara <jack@suse.cz>
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> > So, I'd prefer to restore the default rather than both Redhat and SUSE apply exactly
> > same distro specific patch. because we can easily imazine other users will face the same
> > issue in the future.
> 
> On desktop systems the low dirty limits help maintain interactive feel. 
> Users expect applications that are saving data to be slow. They do not 
> like it when every application in the system randomly comes to a halt 
> because of one program stuffing data up to the dirty limit.

really?
Do you mean our per-task dirty limit wouldn't works?

If so, I think we need fix it. IOW sane per-task dirty limitation seems independent issue 
from per-system dirty limit.


> The cause and effect for the system slowdown is clear when the dirty 
> limit is low. "I saved data and now the system is slow until it is 
> done." When the dirty page ratio is very high, the cause and effect is 
> disconnected. "I was just web surfing and the system came to a halt."
> 
> I think we should expect server admins to do more tuning than desktop 
> users, so the default limits should stay low in my opinion.