Re: MM deadlock [was: Re: arca-vm-8...]

David Lang
1999-01-26T23:32:03Z

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why don'y you spin off your own verion of Linux that only supports that
hardware that you consider "good enough" and let the rest of us go back to
making the system work in the real world where lots of things are not
"good enough" by someones definition.

David Lang

"If users are made to understand that the system administrator's job is to
make computers run, and not to make them happy, they can, in fact, be made
happy most of the time. If users are allowed to believe that the system
administrator's job is to make them happy, they can, in fact, never be made
happy."
- -Paul Evans (as quoted by Barb Dijker in "Managing Support Staff", LISA '97)

On Tue, 26 Jan 1999, Gerard Roudier wrote:

> Date: Tue, 26 Jan 1999 21:48:59 +0100 (MET)
> From: Gerard Roudier <groudier@club-internet.fr>
> To: Thomas Sailer <sailer@ife.ee.ethz.ch>
> Cc: linux-kernel@vger.rutgers.edu, linux-mm@kvack.org
> Subject: Re: MM deadlock [was: Re: arca-vm-8...]
>
>
>
> On Tue, 26 Jan 1999, Thomas Sailer wrote:
>
> > Gerard Roudier wrote:
> >
> > > If you tell me that some system XXX is able to quickly free Mega-Bytes of
> > > physical contiguous memory at any time when it is asked for such a
> >
> > Noone said it has to happen quickly, it's entirely useful even if
> > the calling process (and possibly others) will sleep for 10secs.
> > These allocations are very uncommon, but nevertheless sometimes
> > necessary for some device (drivers).
>
> I suggest to allow some application program to decide what stuff to
> victimize and to be able to tell the kernel about, but not to ask the
> kernel for doing the bad work for you and then critisize it.
>
> > > brain-deaded allocation, then for sure, I will never use system XXX,
> > > because this magic behaviour seems not to be possible without some
> > > paranoid VM policy that may affect badly performances for normal stuff.
> >
> > You may well call the devices that need this broken, the problem
> > is that they are in rather widespread use.
>
> There are bunches of things that are widespread used nowadays and that
> should have disappeard since years if people were a bit more concerned
> by technical and progress considerations.
>
> For example, it seems that 32 bits systems are not enough to provide a
> flat virtual addressing space far larger than the physical address space
> needed for applications (that was the primary goal of virtual memory
> invention). If we were powered a bit more by technical considerations, we
> should drop support of 32 bits systems immediately since as you know 64
> bits systems are available since years and Linux supports them quite well.
>
> Each time we add support or maintain support of crap, we just encourage
> crap and allow the mediocrity to last longer that it really deserves.
>
> A device that requires more contiguous space than 1 PAGE for its
> support is crap. Because designers spared peanuts by not implementing
> address translation tables, we just have to complete their work by
> complexifying O/Ses. The win is 0.02 euro of silicium for them but
> lots of time wasted by O/Ses guys to support the crap.
>
> > If we don't find an algorithm that doesn't affect preformance for
> > the normal stuff, (why would something like selecting
> > a memory region and forcing everything that's currently in the
> > way to be swapped out not work?), then we should probably have
> > a special pool for these "perverse" mappings.
> >
> > But I think there's a rather generic problem: how are you going
> > to support 32bit PCI busmasters in machines with more than
> > 4Gig main memory? It's conceptually the same as how are you
> > going to support ISA DMA with more than 16Meg main memory.
>
> What the ratio of machines that need 4 GB of more for doing their
> work?
> How much does they cost?
> What can we do, if some people that have such machines want to use
> IO controllers that are not able to DMA the whole physical space?
> We just may suggest them to learn or to get help from a psychiatric,
> but we should not accept to waste time trying to make the crap work
> less worse.
>
> > 32bit only PCI busmasters are very common these days, I don't
> > know a single PCI soundcard that can do 64bit master (or even slave)
> > cycles. Also, all PCI soundcards I know which have a hardware
> > wavetable synth (without sample ROM) require ridiculously
> > large contiguous allocations (>= 1M) for the synth to work.
>
> Are you sure a soundcard is really required for systems that run
> with GBs of memory?
>
> > > Anything that requires more that 1 PAGE of physical memory at a time on
> > > running systems is a very bad thing in my opinion. The PAGE is the only
> >
> > Ok, then remove any soundcard from your system. That might be acceptable
> > for you, but probably not for 90% of the Linux users.
>
> A real Linux user is able to make a custom kernel that incorporates some
> driver at boot-up, and can live with that. The ones that are whining about
> their PinkSocket O/S having problem to load the sound driver module at
> run-time is another busyness in my opinion.
>
> Regards,
> Gerard.
>
>
> -
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