From: Arjan van de Ven <arjan@infradead.org>
To: Andrew Morton <akpm@osdl.org>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
open-iscsi@googlegroups.com, ext2-devel@lists.sourceforge.net,
linux-fsdevel@vger.kernel.org, michaelc@cs.wisc.edu,
fujita.tomonori@lab.ntt.co.jp,
Christoph Hellwig <hch@infradead.org>
Subject: Re: allowed pages in the block later, was Re: [Ext2-devel] [PATCH] ext3: avoid sending down non-refcounted pages
Date: Sun, 11 Dec 2005 09:44:04 +0100 [thread overview]
Message-ID: <1134290645.2878.4.camel@laptopd505.fenrus.org> (raw)
In-Reply-To: <20051210164736.6e4eaa3f.akpm@osdl.org>
On Sat, 2005-12-10 at 16:47 -0800, Andrew Morton wrote:
> Christoph Hellwig <hch@infradead.org> wrote:
> >
> > The problem we're trying to solve here is how do implement network block
> > devices (nbd, iscsi) efficiently. The zero copy codepath in the networking
> > layer does need to grab additional references to pages. So to use sendpage
> > we need a refcountable page. pages used by the slab allocator are not
> > normally refcounted so try to do get_page/pub_page on them will break.
>
> I don't get it. Doing get_page/put_page on a slab-allocated page should do
> the right thing?
but it doesn't stop the kfree from freeing the memory; zero copy needs
the content of the memory to stay around afterwards, eg it wants to
delay the kfree until the data is over the wire, which is an
asynchronous event versus the actual send command in a zero-copy
situation.
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next prev parent reply other threads:[~2005-12-11 8:44 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20051208180900T.fujita.tomonori@lab.ntt.co.jp>
[not found] ` <20051208101833.GM14509@schatzie.adilger.int>
2005-12-08 13:42 ` Christoph Hellwig
2005-12-08 13:58 ` Pekka Enberg
2005-12-12 17:27 ` Christoph Hellwig
2005-12-08 18:18 ` Mike Christie
2005-12-08 18:22 ` Mike Christie
2005-12-08 19:20 ` Pekka Enberg
2005-12-11 0:47 ` Andrew Morton
2005-12-11 8:44 ` Arjan van de Ven [this message]
2005-12-12 17:25 ` Christoph Hellwig
2005-12-12 20:12 ` Andrew Morton
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