From: "David S. Miller" <davem@davemloft.net>
To: davidm@hpl.hp.com
Cc: davidm@napali.hpl.hp.com, rohit.seth@intel.com,
linux-ia64@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [patch] arch hook for notifying changes in PTE protections bits
Date: Sun, 20 Mar 2005 00:27:29 +0000 [thread overview]
Message-ID: <20050319162729.12d6789d.davem@davemloft.net> (raw)
In-Reply-To: <16956.35789.229286.442052@napali.hpl.hp.com>
On Sat, 19 Mar 2005 12:30:05 -0800
David Mosberger <davidm@napali.hpl.hp.com> wrote:
> I agree about your concern about cost. Accessing the page_map is
> expensive (integer division + memory access) and we have to do that in
> order to find out if the page is i-cache clean.
First, it's a multiply by reciprocol. At least on sparc64 I get
this emitted by the compiler.
Secondly, if you're willing to sacrifice 8 bytes per page struct
simply define WANT_PAGE_VIRTUAL and page struct will be exactly
64 bytes and thus the divide a will turn into a simple shift.
next prev parent reply other threads:[~2005-03-20 0:27 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20050318162943.A3157@unix-os.sc.intel.com>
2005-03-19 4:05 ` [patch] arch hook for notifying changes in PTE protections bits David S. Miller
2005-03-19 20:22 ` Seth, Rohit
2005-03-19 20:30 ` David Mosberger
2005-03-20 0:27 ` David S. Miller [this message]
2005-03-20 22:38 ` Seth, Rohit
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