Re: Unbloating the kernel, action list

[Gabriel Paubert]

On Thu, Oct 16, 2003 at 07:19:51AM +0200, Jan-Benedict Glaw wrote:
> On Wed, 2003-10-15 20:16:58 +0200, Gabriel Paubert <paubert@xxxxxxx>
> wrote in message <20031015181658.GA9652@xxxxxxx>:
> > On Wed, Oct 15, 2003 at 06:10:15AM -0700, William Lee Irwin III wrote:
> > > On Tue, 2003-10-14 15:56:38 -0700, cliff white <cliffw@xxxxxxxx>
> > > Can you quantify the performance impact of cmov emulation (or whatever
> > > it is)? I have a vague notion it could be hard given the daunting task
> > > of switching userspace around to verify it.
> > The other problem of the 386 is that it has a fundamental MMU flaw:
> > no write protection on kernel mode accesses to user space, which makes 
> > put_user() intrinsically racy on a 386 and way more bloated when it is
> > inlined (access_ok has to call a function which searches the VMA tree).
> 
> However, this problem exists since the very first hour. Linux once
> really ran quite well on those machines...

Yes, but VM sharing between threads was rather infrequent back then
and you need shared VM to create the race.

> 
> I've rebooted my P-Classic router last night. Maybe I can see (in two
> weeks or in a month or the like...) why it slows down, even with 32MB
> RAM...

It might be related to the size-4096 memory leak others are reporting 
right now. I don't know, but it's not such a far-fetched hypothesis
either.

	Gabriel
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