Message-ID: <44580B10.2000205@redhat.com>
Date: Tue, 02 May 2006 18:44:48 -0700
From: Ulrich Drepper <drepper@redhat.com>
Organization: Red Hat, Inc.
User-Agent: Thunderbird 1.5 (X11/20060313)
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To: Blaisorblade <blaisorblade@yahoo.it>
CC: Arjan van de Ven <arjan@linux.intel.com>, linux-kernel@vger.kernel.org,
       Andrew Morton <akpm@osdl.org>, Val Henson <val.henson@intel.com>
Subject: Re: [patch 00/14] remap_file_pages protection support
References: <20060430172953.409399000@zion.home.lan> <1146565266.32045.29.camel@laptopd505.fenrus.org> <200605030226.28047.blaisorblade@yahoo.it>
In-Reply-To: <200605030226.28047.blaisorblade@yahoo.it>
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Blaisorblade wrote:
>> I've not seen much of this if any at all, the various caches that are =
in
>> place for these lookups seem to function quite well; what we did see w=
as
>> glibc's malloc implementation being mistuned resulting in far too many=

>> mmaps than needed (which in turn leads to far too much page zeroing
>> which is the really expensive part. It's not the vma lookup that is
>> expensive, it's the page zeroing)
> Even to this email, I hope Ulrich will answer.

All I can say is that some of our guys tuning a big application on a
customer's site reported seeing the VMA lookups being on the profile
list.  This was some huge Java program.  It might be that every other
page had a different protection, executable or not, read-only mmap etc.
 And data access for very non-local.

I cannot say more since this was near to the end of the trials.

--=20
=E2=9E=A7 Ulrich Drepper =E2=9E=A7 Red Hat, Inc. =E2=9E=A7 444 Castro St =
=E2=9E=A7 Mountain View, CA =E2=9D=96


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