linux-mm.kvack.org archive mirror
 help / color / mirror / Atom feed
From: Nick Piggin <npiggin@suse.de>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Linux Memory Management <linux-mm@kvack.org>,
	Linux-Arch <linux-arch@vger.kernel.org>,
	linux-kernel@vger.kernel.org, linuxppc-dev@ozlabs.org,
	Hugh Dickins <hugh@tiscali.co.uk>
Subject: Re: [RFC/PATCH] mm: Pass virtual address to [__]p{te,ud,md}_free_tlb()
Date: Mon, 20 Jul 2009 12:38:35 +0200	[thread overview]
Message-ID: <20090720103835.GB7070@wotan.suse.de> (raw)
In-Reply-To: <1248084041.30899.7.camel@pasglop>

On Mon, Jul 20, 2009 at 08:00:41PM +1000, Benjamin Herrenschmidt wrote:
> On Mon, 2009-07-20 at 10:10 +0200, Nick Piggin wrote:
> > 
> > Maybe I don't understand your description correctly. The TLB contains
> > PMDs, but you say the HW still logically performs another translation
> > step using entries in the PMD pages? If I understand that correctly,
> > then generic mm does not actually care and would logically fit better
> > if those entries were "linux ptes". 
> 
> They are :-)
> 
> > The pte invalidation routines
> > give the virtual address, which you could use to invalidate the TLB.
> 
> For PTEs, yes, but not for those PMD entries. IE. I need the virtual
> address when destroying PMDs so that I can invalidate those "indirect"
> pages. PTEs are already taken care of by existing mechanisms.

Hmm, so even after having invalidated all the pte translations
then you still need to invalidate the empty indirect page? (or
maybe you don't even invalidate the ptes if they're not cached
in a TLB).

I believe x86 is also allowed to cache higher level page tables
in non-cache coherent storage, and I think it just avoids this
issue by flushing the entire TLB when potentially tearing down
upper levels. So in theory I think your patch could allow x86 to
use invlpg more often as well (in practice the flush-all case
and TLB refills are so fast in comparison with invlpg that it
probably doesn't gain much especially when talking about
invalidating upper levels). So making the generic VM more
flexible like that is no problem for me.

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>

  reply	other threads:[~2009-07-20 10:38 UTC|newest]

Thread overview: 24+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2009-07-15  7:49 [RFC/PATCH] mm: Pass virtual address to [__]p{te,ud,md}_free_tlb() Benjamin Herrenschmidt
2009-07-15 13:56 ` Nick Piggin
2009-07-16  1:54   ` Benjamin Herrenschmidt
2009-07-20  8:10     ` Nick Piggin
2009-07-20 10:00       ` Benjamin Herrenschmidt
2009-07-20 10:38         ` Nick Piggin [this message]
2009-07-21  0:02           ` Benjamin Herrenschmidt
2009-07-21  7:05             ` Nick Piggin
2009-07-20  7:11   ` Benjamin Herrenschmidt
2009-07-20  7:48     ` Martin Schwidefsky
2009-07-20  8:05     ` Nick Piggin
2009-07-20  9:59       ` Benjamin Herrenschmidt
2009-07-20 10:39         ` Nick Piggin
2009-07-22 16:31     ` Linus Torvalds
2009-07-23  0:53       ` Benjamin Herrenschmidt
2009-07-23  0:59         ` Kumar Gala
2009-07-27 19:11         ` Linus Torvalds
2009-07-27 21:35           ` Benjamin Herrenschmidt
2009-07-28  0:17           ` Benjamin Herrenschmidt
2009-07-28  0:25             ` Paul Mundt
2009-07-28  0:41               ` Linus Torvalds
2009-07-16  1:36 ` Michael Ellerman
2009-07-16  1:56   ` Benjamin Herrenschmidt
2009-07-20 12:46 ` David Howells

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=20090720103835.GB7070@wotan.suse.de \
    --to=npiggin@suse.de \
    --cc=benh@kernel.crashing.org \
    --cc=hugh@tiscali.co.uk \
    --cc=linux-arch@vger.kernel.org \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=linuxppc-dev@ozlabs.org \
    /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
Be sure your reply has a Subject: header at the top and a blank line before the message body.
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).