linux-kernel - Re: DOS by unprivileged user

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Message-ID: <12218300.6oQjICIiUq@ferry-quad>
Date:   Mon, 30 Apr 2018 12:00:16 +0200
From:   Ferry Toth <ftoth@...fort.nl>
To:     Alan Cox <gnomes@...rguk.ukuu.org.uk>
Cc:     Mike Galbraith <efault@....de>, linux-kernel@...r.kernel.org
Subject: Re: DOS by unprivileged user

Op woensdag 25 april 2018 16:54:59 CEST schreef Alan Cox:
> > > I think memory allocation and io waits can't be decoupled from
> > > scheduling as they are now.  
> > 
> > The scheduler is not decoupled from either, it is intimately involved
> > in both.  However, none of the decision making smarts for either reside
> > in the scheduler, nor should they.
> 
> It belongs in both.
> 
> Classical Unix systems never had this problem because they respond to
> thrashing by ensuring that all processes consumed CPU and made some
> progress. Linux handles it by thrashing itself to dealth while BSD always
> handled it by moving from paging more towards swapping and behaving like
> a swap bound batch machine.
> 
> Linux thrashes itself to death, the classic BSD algorithn instead throws
> fairness out of the window under extreme load to prevent it. It might take
> a few seconds but at least you will get your prompt back.
> 
> Alan
> 
I haven.t tried BSD.

But when I was young I allocated 10MB on a HP9000 (UX) with 1MB of RAM. People wanted to launch me out of the window (18th floor).

I did not want to say Unix was better, only with so much emphasis on security I'.m surprised how easy it is for a regular user to bring linux to on it.s knees.