Re: Heads-up: random hangs with Linux 5.7-rc4 on PowerMac6,7 (and other minor issues)
On Sun, May 10, 2020 at 01:09:58PM +0100, Rui Salvaterra wrote:
> Hi, Gabriel,
>
> On Sun, 10 May 2020 at 12:37, Gabriel Paubert <paubert@iram.es> wrote:
> >
> > I suspect the PowerMac6,7 is a 32 bit machine, given what you say below.
>
> Yes, of course, sorry for not being more explicit. :)
>
> > Well, extremely low is a bit of an exaggeration. On 32 bit x86, lowmem
> > is 896MB. This is only 128MB higher than on your machine, or 16.7% more.
>
> My surprise wasn't the HIGHMEM split itself, but the fact that it's
> needed at all. I have x86(-32) machines with over 3 GiB of usable RAM
> which don't need HIGHMEM support.
Huh ? User space is 3GB on x86, but kernel uses highmem as soon as there
is over ~1GB of physical RAM.
And if I remember correctly user applications can also map 3GB on PPC32,
4GB on PPC32 applications running on 64 bit machines.
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