From mboxrd@z Thu Jan  1 00:00:00 1970
X-Spam-Checker-Version: SpamAssassin 3.4.5-pre1 (2020-06-20) on
	ip-172-31-74-118.ec2.internal
X-Spam-Level: 
X-Spam-Status: No, score=-1.9 required=3.0 tests=BAYES_00 autolearn=ham
	autolearn_force=no version=3.4.5-pre1
Path: eternal-september.org!reader02.eternal-september.org!.POSTED!not-for-mail
From: Paul Rubin <no.email@nospam.invalid>
Newsgroups: comp.lang.ada
Subject: Re: is there a version of unix written in Ada
Date: Thu, 01 Oct 2020 02:46:50 -0700
Organization: A noiseless patient Spider
Message-ID: <87o8lml1md.fsf@nightsong.com>
References: <e3c51e65-b71e-4623-bd58-c94cdbcc3ba6o@googlegroups.com>
	<00cd3aaa-d518-43a2-b321-58d6fae70aebo@googlegroups.com>
	<db65f550-c1d9-4ddb-b128-7e4e9c1f818bn@googlegroups.com>
	<57eb7a65-51ea-4624-b9dc-9c4dda0fee59n@googlegroups.com>
	<rkq9gr$s0u$1@gioia.aioe.org> <5f70fd3b$0$13541$426a74cc@news.free.fr>
	<rks433$ndr$1@gioia.aioe.org>
	<daa04c57-0dfa-4c95-84ef-0e90f3c1732cn@googlegroups.com>
	<rkst48$171u$1@gioia.aioe.org> <87wo0d3iac.fsf@nightsong.com>
	<rkth03$uk5$1@gioia.aioe.org> <87sgb02l7b.fsf@nightsong.com>
	<rl1f1i$le8$1@gioia.aioe.org> <875z7vyy1u.fsf@nightsong.com>
	<rl2n2q$ddt$1@gioia.aioe.org> <87wo0bkns3.fsf@nightsong.com>
	<rl2rqt$jdq$1@gioia.aioe.org> <87sgayl6o0.fsf@nightsong.com>
	<rl47bk$1nn9$1@gioia.aioe.org>
Mime-Version: 1.0
Content-Type: text/plain
Injection-Info: reader02.eternal-september.org; posting-host="6c29d653826c2f3c1574687a7e172b7c";
	logging-data="18643"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1/UR2HdsRyc7bhjO6Gjn1y5"
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.1 (gnu/linux)
Cancel-Lock: sha1:DgJAEU5aR3ozjnuJRUl+bDSB3uE=
	sha1:qiJOSJKdog9O94xza2IdwrcdL7w=
Xref: reader02.eternal-september.org comp.lang.ada:60352
List-Id: <comp.lang.ada>

"Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
>> You have that either way.
> That is the point.

With a conventional OS you have those synchronization delays AND
you have address translation delays.  With Singularity you still
have the first, but you get rid of the second.

> So, where is performance gain? You still need storing/restoring
> registers and other context's data upon preemting.

You run millions of instructions between preemptions, but you take the
address translation delay on EVERY memory access.

> Are you going to recompile and re-link everything in
> absolute addresses every time anything changes and then reboot?

Position independent code is a thing.

> Neither can do anything about it. You either have abstraction, like
> flat contiguous address space, however implemented, or you do not. The
> penalty is always there. You can have some relief from the hardware or
> none.

Shrug, maybe there is some kind of block allocator like in the old days.
The original purpose of virtual memory was to allow simulating big ram
by paging to disk.  Nobody cares about that any more.

That said, I don't know much about Singularity (never used it, haven't
read the papers) so maybe I'm missing something important.  But the guys
who told me about it were knowledgeable and they were impressed by it.

Anyway, this tangent started from the claim that nothing different had
been done in OS's in a while.  I don't claim Singularity is great, only
that it's different.