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Newsgroups: comp.sys.3b1
Date: Mon, 24 Oct 2022 04:19:37 -0700 (PDT)
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Subject: Re: How to activate swap?
From: Peter Schmidt <peter@transcend.aero>
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Xref: csiph.com comp.sys.3b1:683

The ported memory architecture is a sad waste of a 32 bit microprocessor's =
potential. Only machines I've ever had where physical memory was greater th=
an per process virtual memory.

On Monday, October 24, 2022 at 2:40:22 AM UTC-4, Alain Knaff wrote:
> Hi Jesse,
> On 24/10/2022 07:45, J Booth wrote:=20
>=20
> > Hi Alain.=20
> >=20
> >>> I conclude by this that only about 2.5MB are available in *total*=20
> > So it hit me today, I recall seeing the memory map for the 4MB RAM addr=
ess space (0x0 - 0x3FFFFF), and sure enough, only around 2.5 MB allocated t=
o user processes:=20
> >=20
> > KERNEL ONLY =3D 00_00_00 =E2=80=93 07_FF_FF (512 KB)=20
> > User Process =3D 08_00_00 =E2=80=93 2F_FF_FF (2.5 MB)=20
> > Shared Lib =3D 30_00_00 =E2=80=93 37_FF_FF (512 KB)
> Yes, I have figured this out since then
> > Kernel VM =3D 38_00_00 =E2=80=93 3F_FF_FF (512 KB)
> That bit I didn't know yet. As far as I know, Linux does the same (i.e.=
=20
> the kernel exists in the application's address space, even though=20
> inaccessible to the application, obviously)
> >=20
> > So I don't think increasing swap is going to help much given the limite=
d address space.
> Actually, the problem that I used to have was running "many" *processes*=
=20
> concurrently.=20
>=20
> When configuring a software package using GNU autoconf, at some point in=
=20
> time there's a multi-step pipeline and each step implies needs an=20
> additional shell process. With ksh or bash (containing a full load of=20
> config variables), and just 3 or 4 steps of pipeline, this was enough to=
=20
> run out of VM. Adding more swap resolved the issue. Back then, I did add=
=20
> more swap "the hard way" by re-installing from floppies and choosing=20
> more swap at the appropriate step. But nowadays, I just use dgesswein's=
=20
> s4vol tool=20
> Next challenge is to get gcc-3.3.6 (running on UnixPC) to compile a=20
> program longer than a simple hello-world. It runs out of memory pretty=20
> quickly, and as this is one process, swap does not help that use case.=20
>=20
> >=20
> > Jesse=20
> >=20
>=20
> Regards,=20
>=20
> Alain