From: Andrea Arcangeli <andrea@suse.de>
To: Andrew Morton <akpm@osdl.org>
Cc: marcelo.tosatti@cyclades.com, mason@suse.com,
linux-kernel@vger.kernel.org
Subject: Re: Unnecessary barrier in sync_page()?
Date: Wed, 7 Jul 2004 20:42:02 +0200 [thread overview]
Message-ID: <20040707184202.GN28479@dualathlon.random> (raw)
In-Reply-To: <20040707112953.0157383e.akpm@osdl.org>
On Wed, Jul 07, 2004 at 11:29:53AM -0700, Andrew Morton wrote:
> Andrea Arcangeli <andrea@suse.de> wrote:
> >
> > however the smp_mb() isn't needed in sync_page, simply because it's
> > perfectly ok if we start running sync_page before reading pagelocked.
> > All we care about is to run sync_page _before_ io_schedule() and that we
> > read PageLocked _after_ prepare_to_wait_exclusive.
> >
> > So the locking in between PageLocked and sync_page is _absolutely_
> > worthless and the smp_mb() can go away.
>
> IIRC, Chris added that barrier (and several similar) for the reads in
> page_mapping().
how does it help to know the page is not locked before executing
page_mapped?
next prev parent reply other threads:[~2004-07-07 18:42 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-07-07 17:57 Unnecessary barrier in sync_page()? Marcelo Tosatti
2004-07-07 18:20 ` Andrea Arcangeli
2004-07-07 18:29 ` Andrew Morton
2004-07-07 18:42 ` Andrea Arcangeli [this message]
2004-07-07 18:46 ` Andrea Arcangeli
2004-07-07 20:57 ` Chris Mason
2004-07-07 21:06 ` Andrea Arcangeli
2004-07-07 21:15 ` Chris Mason
2004-07-07 21:30 ` Andrew Morton
2004-07-07 21:34 ` Chris Mason
2004-07-07 22:02 ` Andrea Arcangeli
2004-07-07 22:27 ` Andrew Morton
2004-07-07 18:58 ` Marcelo Tosatti
2004-07-07 19:12 ` Andrea Arcangeli
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