On Fri, Aug 16, 2013 at 7:59 AM, Ingo Jürgensmann <[email protected]>
wrote:
> Am 13.08.2013 um 11:14 schrieb Geert Uytterhoeven <[email protected]>:
>>> 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 -- [email protected]
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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