From: Nick Piggin <npiggin@suse.de>
To: Christoph Lameter <clameter@sgi.com>
Cc: Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-fsdevel@vger.kernel.org
Subject: Re: [RFC] fsblock
Date: Tue, 10 Jul 2007 03:07:58 +0200 [thread overview]
Message-ID: <20070710010757.GD8779@wotan.suse.de> (raw)
In-Reply-To: <Pine.LNX.4.64.0707091756020.2348@schroedinger.engr.sgi.com>
On Mon, Jul 09, 2007 at 05:59:47PM -0700, Christoph Lameter wrote:
> On Tue, 10 Jul 2007, Nick Piggin wrote:
>
> > > Hmmm.... I did not notice that yet but then I have not done much work
> > > there.
> >
> > Notice what?
>
> The bad code for the buffer heads.
Oh. Well my first mail in this thrad listed some of the problems
with them.
> > > > - A real "nobh" mode. nobh was created I think mainly to avoid problems
> > > > with buffer_head memory consumption, especially on lowmem machines. It
> > > > is basically a hack (sorry), which requires special code in filesystems,
> > > > and duplication of quite a bit of tricky buffer layer code (and bugs).
> > > > It also doesn't work so well for buffers with non-trivial private data
> > > > (like most journalling ones). fsblock implements this with basically a
> > > > few lines of code, and it shold work in situations like ext3.
> > >
> > > Hmmm.... That means simply page struct are not working...
> >
> > I don't understand you. jbd needs to attach private data to each bh, and
> > that can stay around for longer than the life of the page in the pagecache.
>
> Right. So just using page struct alone wont work for the filesystems.
>
> > There are no changes to the filesystem API for large pages (although I
> > am adding a couple of helpers to do page based bitmap ops). And I don't
> > want to rely on contiguous memory. Why do you think handling of large
> > pages (presumably you mean larger than page sized blocks) is strange?
>
> We already have a way to handle large pages: Compound pages.
Yes but I don't want to use large pages and I am not going to use
them (at least, they won't be mandatory).
> > Conglomerating the constituent pages via the pagecache radix-tree seems
> > logical to me.
>
> Meaning overhead to handle each page still exists? This scheme cannot
> handle large contiguous blocks as a single entity?
Of course some things have to be done per-page if the pages are not
contiguous. I actually haven't seen that to be a problem or have much
reason to think it will suddenly become a problem (although I do like
Andrea's config page sizes approach for really big systems that cannot
change their HW page size).
next prev parent reply other threads:[~2007-07-10 1:08 UTC|newest]
Thread overview: 53+ messages / expand[flat|nested] mbox.gz Atom feed top
2007-06-24 1:45 [RFC] fsblock Nick Piggin
2007-06-24 1:46 ` [patch 1/3] add the fsblock layer Nick Piggin
2007-06-24 15:28 ` Andi Kleen
2007-06-24 20:18 ` Arjan van de Ven
2007-06-25 8:58 ` Andi Kleen
2007-06-25 7:19 ` Nick Piggin
2007-06-24 23:01 ` Neil Brown
2007-06-25 7:41 ` Nick Piggin
2007-06-25 12:29 ` Chris Mason
2007-06-26 2:34 ` Nick Piggin
2007-06-26 2:48 ` Neil Brown
2007-06-26 3:07 ` Nick Piggin
2007-06-26 12:26 ` Chris Mason
2007-06-30 10:40 ` Christoph Hellwig
2007-06-30 10:40 ` Christoph Hellwig
2007-06-25 13:19 ` Chris Mason
2007-06-26 2:42 ` Nick Piggin
2007-06-24 1:46 ` [patch 2/3] block_dev: convert to fsblock Nick Piggin
2007-06-24 1:47 ` [patch 3/3] minix: " Nick Piggin
2007-06-24 1:53 ` [RFC] fsblock Nick Piggin
2007-06-24 3:07 ` Jeff Garzik
2007-06-24 3:47 ` Nick Piggin
2007-06-24 13:51 ` Chris Mason
2007-06-25 6:58 ` Nick Piggin
2007-06-25 12:25 ` Chris Mason
2007-06-30 10:44 ` Christoph Hellwig
2007-06-30 10:42 ` Christoph Hellwig
2007-06-30 11:10 ` Jeff Garzik
2007-06-30 11:13 ` Christoph Hellwig
2007-06-24 4:19 ` William Lee Irwin III
2007-06-24 14:16 ` Andi Kleen
2007-06-25 7:16 ` Nick Piggin
2007-06-26 3:06 ` David Chinner
2007-06-26 3:55 ` Nick Piggin
2007-06-26 9:23 ` David Chinner
2007-06-26 11:14 ` Nick Piggin
2007-06-27 12:39 ` Kyle Moffett
2007-06-26 12:34 ` Chris Mason
2007-06-27 5:32 ` Nick Piggin
2007-06-27 6:05 ` David Chinner
2007-06-27 11:50 ` Chris Mason
2007-06-27 15:18 ` Anton Altaparmakov
2007-06-27 22:35 ` David Chinner
2007-06-28 2:44 ` Nick Piggin
2007-06-28 12:20 ` Chris Mason
2007-06-29 2:08 ` David Chinner
2007-06-29 2:33 ` Nick Piggin
2007-06-30 11:05 ` Christoph Hellwig
2007-07-09 17:14 ` Christoph Lameter
2007-07-10 0:54 ` Nick Piggin
2007-07-10 0:59 ` Christoph Lameter
2007-07-10 1:07 ` Nick Piggin [this message]
2007-07-10 1:37 ` Dave McCracken
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