Date: Thu, 28 Aug 2003 01:21:52 -0700
From: Andrew Morton <akpm@osdl.org>
To: Rusty Russell <rusty@rustcorp.com.au>
Cc: mingo@redhat.com, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 2/2] Futex non-page-pinning fix
Message-Id: <20030828012152.1294f183.akpm@osdl.org>
In-Reply-To: <20030828080403.DC3272C640@lists.samba.org>
References: <20030826232039.626f5a4c.akpm@osdl.org>
	<20030828080403.DC3272C640@lists.samba.org>
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Rusty Russell <rusty@rustcorp.com.au> wrote:
>
> > I think a better place to rehash the futex would be at the point where the
>  > page is added to and removed from swapcache.
> 
>  This is simplest: the current code actually moves the futex queue out
>  of the hash.  If we make the rule: "call futex_rehash" every time
>  page->mapping (or page->index) changes, we avoid races and make the
>  code simpler.
> 
>  But this means it could be called quite often.

Moving pages to and from swapcache really is not a fastpath at all,
so I wouldn't be worrying about that.

And even if the code is sucky, it will only be sucky when there is a lot of
swapcache activity AND a lot of futexes are in use.


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