Re: Multiple Memory Chunks
On Fri, Aug 16, 2013 at 7:59 AM, Ingo Jürgensmann <ij@2013.bluespice.org> wrote:
> Am 13.08.2013 um 11:14 schrieb Geert Uytterhoeven <geert@linux-m68k.org>:
>>> Yes, and I would like to avoid this, of course. ;-) It really slows down the machine and you can even feel it... ;)
>> We may also use the slow mainboard RAM (I get ca. 12 MiB/s) as a fast swap
>> device.
>
> I would like to avoid using those kind of RAM as swap. Reasons:
> - it would add an additional layer of paging in/out. Even if it is comparable fast, pages of data and code would need to swapped in and out.
> - to make sense it would need an higher swap priority to get used first, but then again it will most likey result in being filled with something that accidently gets swapped out first, whereas stuff that gets frequently used and swapped in/out will still be swapped to disk.
> - to avoid this we would need some kind of write through cache like it's often used for SSD hybrid disks where stuff that is often needed will reside within SSD side of that hybrid disks while other stuff will be stored on the slower spinning disk.
IIRC, Linux itself now also has a software variant of the SSD hybrid
disk approach.
So we could use that on a RAM block device instead of an SSD.
>>>> Now why do you have a memfile like this: a long time ago, the m68k kernel
>>>> used its own mapping code for system RAM, where virtual and physical
>>>
>>> Remember that there were problems with loading 3.2.0-4-amiga without the memfile.
>> Yes, going out of memory when allocating the page table arrays? That won't
>> improve when adding 256 MiB of Z3 RAM in the far end of the physical
>> address space...
>
> No, but we would have more memory to waste for this. Excluding 8 MB for this from 128 MB does hurt more than 8 MB out of 384 MB. ;)
I mean that we would waste more memory too, due to the Z3 RAM being far from
the rest of RAM in the address space.
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-m68k.org
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
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