From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53982) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VMhza-00061p-IX for qemu-devel@nongnu.org; Thu, 19 Sep 2013 13:26:19 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1VMhzV-0002SZ-MT for qemu-devel@nongnu.org; Thu, 19 Sep 2013 13:26:14 -0400 Received: from mx1.redhat.com ([209.132.183.28]:21548) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1VMhzV-0002SS-E5 for qemu-devel@nongnu.org; Thu, 19 Sep 2013 13:26:09 -0400 Received: from int-mx01.intmail.prod.int.phx2.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id r8JHQ8lI008605 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK) for ; Thu, 19 Sep 2013 13:26:08 -0400 Message-ID: <523B33AF.8090607@redhat.com> Date: Thu, 19 Sep 2013 11:26:07 -0600 From: Eric Blake MIME-Version: 1.0 References: <1378106712-29856-1-git-send-email-mreitz@redhat.com> <523B134C.8060902@redhat.com> In-Reply-To: <523B134C.8060902@redhat.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="fOXrSUtx4o0eKbweBNdQDh9p4rCR1QNaj" Subject: Re: [Qemu-devel] [PATCH v5 0/8] Add metadata overlap checks List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Max Reitz Cc: Kevin Wolf , qemu-devel@nongnu.org, Stefan Hajnoczi This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --fOXrSUtx4o0eKbweBNdQDh9p4rCR1QNaj Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable On 09/19/2013 09:07 AM, Max Reitz wrote: > Hi, >=20 > I've done some benchmarks regarding this series now. In particular, I'v= e > created a 7G image, installed Arch Linux to a partition in the first 2G= > and created an empty ext4 partition for benchmarking in the remaining 5= G. Thank you for doing this! >=20 > Basically, I didn't get any results which indicate a performance hit. >=20 > All in all, I don't see any significant performance difference when > benchmarking on a tmpfs (which should maximize the overhead of > "constant" and "cached") and the data from my HDD benchmarks is probabl= y > stastically unusable. The only comparison which they would have been > useful for are the comparison of "all" to "cached", but since "all" wil= l > not be the default (and anyone explicitly using this option is in fact > responsible for slow I/O himself)) they aren't actually that important > anyway. That's good news. Remember, my question about whether we needed the ability for command-line tuning was conditional on whether the tuning would make a difference - but if you aren't seeing a difference with your benchmark, then we might as well unconditionally enable the checking, and not worry about the complexity of exposing additional tuning. Simpler is better if it makes no difference in end. [Of course, if you WANT to write the patches for making it configurable, I won't stop you; but now that you answered my question about performance, and the answer is the desirable "no measurable impact", I don't know that I would ever plan on using such tuning] --=20 Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org --fOXrSUtx4o0eKbweBNdQDh9p4rCR1QNaj Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.14 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Thunderbird - http://www.enigmail.net/ iQEcBAEBCAAGBQJSOzOvAAoJEKeha0olJ0NqVvEH/0RNbP+5mdMSygsvGrn0wTrl ZIoUE1NMAXAHMOApww6dAje5KR0UVgdtUsr9I+/159NFgLcHQ85lahXJTjahgY1N 6MUXitgYUSONiDu5BVJz1inlxi6l12tQKvhFs/gZjhQ5GZeekBvLdUBO98s5qtgU O92DUi+Kcr5OpCDgc/OOa5s+eB1bHSAEFoxY4MN7WhkU7j90tQ4oWwyc8MwaSOCl 4jg7f9y8Lmby7hW1z1wA8UjU/b6PTq6Au4sStyg2d82z6YEQq1QfIo6L4+EtOI3k 6YC3ehRN8BzuVBvYxYDH/3V3DweDmVKZ9ISOhdVPxkZs/D8XPXSXohRwpfjXgcw= =PtnX -----END PGP SIGNATURE----- --fOXrSUtx4o0eKbweBNdQDh9p4rCR1QNaj--