LKML Archive on lore.kernel.org
help / color / mirror / Atom feed
From: "Yinghai Lu" <yhlu.kernel@gmail.com>
To: "Ingo Molnar" <mingo@elte.hu>
Cc: "Thomas Gleixner" <tglx@linutronix.de>,
	"H. Peter Anvin" <hpa@zytor.com>,
	"Linux Kernel Mailing List" <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] x86_64: fix page table size
Date: Thu, 7 Feb 2008 00:36:18 -0800	[thread overview]
Message-ID: <86802c440802070036w1aced44ft8ab880e8ddeedc85@mail.gmail.com> (raw)
In-Reply-To: <20080207080930.GB28631@elte.hu>

On Feb 7, 2008 12:09 AM, Ingo Molnar <mingo@elte.hu> wrote:
>
> * Yinghai Lu <Yinghai.Lu@Sun.COM> wrote:
>
> > [PATCH] x86_64: fix page table size
>
> > Entering add_active_range(0, 1048576, 67239936) 2 entries of 3200 used
> > end_pfn_map = 67239936
> > Kernel panic - not syncing: Overlapping early reservations 8000-109fff
> > PGTABLE to 9bc00-9dbff EBDA
> >
> > change back the logic. we DO need extra space for pmds when
> > direct_gbpages is not there.
>
> > @@ -370,7 +370,7 @@ static void __init find_early_table_space(unsigned long end)
> >
> >       puds = (end + PUD_SIZE - 1) >> PUD_SHIFT;
> >       tables = round_up(puds * sizeof(pud_t), PAGE_SIZE);
> > -     if (direct_gbpages) {
> > +     if (!direct_gbpages) {
>
> thanks Yinghai, applied!
>
> I'm wondering why this bug didnt trigger more widely. It seems to me it
> needs some serious amount of RAM to trigger this bug - correct?

yes.  need 256g.
128g without patch it still work. because round_up(.., PAGE_SIZE) get
some extra.

>
> btw., it would be nice to have some "lots of RAM simulation" debugging
> code which would just _fake_ a really large e820 map and would in the
> end throw away the 'fake' pages later during bootup. Perhaps tell the
> early allocator to never allocate into these fake areas [via an struct
> e820 entry flag], but all our sizing code and the boot bitmaps, etc.
> would be sized accordingly, as if we had this much RAM - and we'd
> trigger these nuances. We could put this into a new "fakemem=128GB" boot
> option and hence we could boot with fakemem=128GB on a 2GB box and could
> at least hope to be able to boot [with some serious amount of RAM wasted
> on over-sized pagetables, allocator bitmaps and mem_map[]]. Hm?

sound interesting. but need some variable to prevent using non exist page.

YH

  reply	other threads:[~2008-02-07  8:36 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2008-02-06 20:46 my config doesnt compile in your tree Yinghai Lu
2008-02-06 21:53 ` Ingo Molnar
2008-02-06 23:01   ` Yinghai Lu
     [not found]     ` <20080206231226.GA6417@elte.hu>
2008-02-07  4:22       ` [PATCH] x86_64: fix page table size Yinghai Lu
2008-02-07  4:23         ` [PATCH] x86_64: clean up find_e820_area Yinghai Lu
2008-02-07  8:12           ` Ingo Molnar
2008-02-07  7:23         ` [PATCH] x86_64: fix page table size Andi Kleen
2008-02-07 11:54           ` Ingo Molnar
2008-02-07 17:28             ` Andi Kleen
2008-02-07  8:09         ` Ingo Molnar
2008-02-07  8:36           ` Yinghai Lu [this message]
2008-02-07  8:49             ` Ingo Molnar

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=86802c440802070036w1aced44ft8ab880e8ddeedc85@mail.gmail.com \
    --to=yhlu.kernel@gmail.com \
    --cc=hpa@zytor.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=mingo@elte.hu \
    --cc=tglx@linutronix.de \
    --subject='Re: [PATCH] x86_64: fix page table size' \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link

This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).