From: Ben Hutchings <ben@decadent.org.uk>
To: Greg KH <gregkh@suse.de>
Cc: linux-kernel@vger.kernel.org, stable@kernel.org,
        Ingo Molnar <mingo@elte.hu>, kexec@lists.infradead.org,
        Cliff Wickman <cpw@sgi.com>, akpm@linux-foundation.org,
        torvalds@linux-foundation.org, stable-review@kernel.org,
        alan@lxorguk.ukuu.org.uk
In-Reply-To: <20101119214410.087440440@clark.site>
References: <20101119214410.087440440@clark.site>
Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-xspl/jbONpB3o2YLR3IV"
Date: Sat, 20 Nov 2010 02:16:12 +0000
Message-ID: <1290219372.3818.113.camel@localhost>
Mime-Version: 1.0
Subject: Re: [Stable-review] [08/45] mm, x86: Saving vmcore with non-lazy
 freeing of vmas
Sender: linux-kernel-owner@vger.kernel.org
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On Fri, 2010-11-19 at 13:42 -0800, Greg KH wrote:
> 2.6.32-stable review patch.  If anyone has any objections, please let us =
know.
>=20
> ------------------
>=20
> From: Cliff Wickman <cpw@sgi.com>
>=20
> commit 3ee48b6af49cf534ca2f481ecc484b156a41451d upstream.
>=20
> During the reading of /proc/vmcore the kernel is doing
> ioremap()/iounmap() repeatedly. And the buildup of un-flushed
> vm_area_struct's is causing a great deal of overhead. (rb_next()
> is chewing up most of that time).
>=20
> This solution is to provide function set_iounmap_nonlazy(). It
> causes a subsequent call to iounmap() to immediately purge the
> vma area (with try_purge_vmap_area_lazy()).
>=20
> With this patch we have seen the time for writing a 250MB
> compressed dump drop from 71 seconds to 44 seconds.
[...]

Useful, but it doesn't seem to meet the criteria for stable updates.

Ben.

--=20
Ben Hutchings
Once a job is fouled up, anything done to improve it makes it worse.

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