From: Pavel Machek <pavel@ucw.cz>
To: Alan Cox <gnomes@lxorguk.ukuu.org.uk>
Cc: Joerg Roedel <jroedel@suse.de>, Meelis Roos <mroos@linux.ee>,
Thomas Gleixner <tglx@linutronix.de>,
Linux Kernel list <linux-kernel@vger.kernel.org>,
linux-mm@kvack.org, Andrea Arcangeli <aarcange@redhat.com>,
Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: 32-bit PTI with THP = userspace corruption
Date: Sun, 21 Oct 2018 14:37:45 +0200 [thread overview]
Message-ID: <20181021123745.GA26042@amd> (raw)
In-Reply-To: <20180918140030.248afa21@alans-desktop>
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On Tue 2018-09-18 14:00:30, Alan Cox wrote:
> On Tue, 11 Sep 2018 14:12:22 +0200
> Joerg Roedel <jroedel@suse.de> wrote:
>
> > On Tue, Sep 11, 2018 at 02:58:10PM +0300, Meelis Roos wrote:
> > > The machines where I have PAE off are the ones that have less memory.
> > > PAE is off just for performance reasons, not lack of PAE. PAE should be
> > > present on all of my affected machines anyway and current distributions
> > > seem to mostly assume 686 and PAE anyway for 32-bit systems.
> >
> > Right, most distributions don't even provide a non-PAE kernel for their
> > users anymore.
> >
> > How big is the performance impact of using PAE over legacy paging?
>
> On what system. In the days of the original 36bit PAE Xeons it was around
> 10% when we measured it at Red Hat, but that was long ago and as you go
> newer it really ought to be vanishingly small.
>
> There are pretty much no machines that don't support PAE and are still
> even vaguely able to boot a modern Linux kernel. The oddity is the
> Pentium-M but most distros shipped a hack to use PAE on the Pentium M
> anyway as it seems to work fine.
I do have some AMD Geode here, in form of subnotebook. Definitely
newer then Pentium Ms, but no PAE...
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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next prev parent reply other threads:[~2018-10-21 12:38 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-08-30 18:09 32-bit PTI with THP = userspace corruption Meelis Roos
2018-08-30 20:55 ` Joerg Roedel
2018-08-31 4:12 ` Meelis Roos
2018-08-31 7:07 ` Joerg Roedel
2018-09-08 10:24 ` Thomas Gleixner
2018-09-11 11:49 ` Joerg Roedel
2018-09-11 11:58 ` Meelis Roos
2018-09-11 12:12 ` Joerg Roedel
2018-09-18 13:00 ` Alan Cox
2018-10-21 12:37 ` Pavel Machek [this message]
2018-10-22 7:56 ` Joerg Roedel
2018-10-22 18:48 ` Alan Cox
2018-10-23 9:11 ` Not-so-old machines without PAE was " Pavel Machek
2018-10-22 20:56 ` Pavel Machek
2018-09-11 18:20 ` Linus Torvalds
2018-08-31 7:10 ` Meelis Roos
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