From: Artem Bityutskiy Subject: Re: [PATCHv4 3/5] ext4: remove unnecessary superblock dirtying Date: Tue, 10 Jul 2012 15:17:29 +0300 Message-ID: <1341922649.2963.94.camel@sauron> References: <1341404514-13660-1-git-send-email-dedekind1@gmail.com> <1341404514-13660-4-git-send-email-dedekind1@gmail.com> <20120704131124.GA29954@quack.suse.cz> Reply-To: dedekind1@gmail.com Mime-Version: 1.0 Content-Type: multipart/signed; micalg="pgp-sha1"; protocol="application/pgp-signature"; boundary="=-g8v1ShFN8TOJjY8zEqUL" Cc: Theodore Tso , Linux FS Maling List , Linux Kernel Maling List , Ext4 Mailing List To: Jan Kara Return-path: In-Reply-To: <20120704131124.GA29954@quack.suse.cz> Sender: linux-kernel-owner@vger.kernel.org List-Id: linux-ext4.vger.kernel.org --=-g8v1ShFN8TOJjY8zEqUL Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, 2012-07-04 at 15:11 +0200, Jan Kara wrote: > On Wed 04-07-12 15:21:52, Artem Bityutskiy wrote: > > From: Artem Bityutskiy > >=20 > > This patch changes the '__ext4_handle_dirty_super()' function which is = used > > by ext4 to update the superblock via the journal in the following cases= : > >=20 > > 1. When creating the first large file on a file system without > > EXT4_FEATURE_RO_COMPAT_LARGE_FILE feature. > > 2. When re-sizing the file-system. > > 3. When creating an xattr on a file-system without the > > EXT4_FEATURE_COMPAT_EXT_ATTR feature. > > 4. When adding or deleting an orphan (because we update the 's_last_orp= han' > > superblock field). > >=20 > > This function, however, falls back to just marking the superblock as di= rty > > if the file-system has no journal. This means that we delay the actual > > superblock I/O submission by 5 seconds (roughly speaking). Namely, the > > 'sync_supers()' kernel thread will call 'ext4_write_super()' later, whe= re > > we actually will submit the superblock down to the media. > >=20 > > However: > > 1. For cases 1-3 it does not add any value to delay the I/O submission.= These > > events are rare and we may just commit submit the superblock for > > asynchronous I/O right away. > > 2. For case 4 - similarly, not terribly frequent event in most of workl= oads. > > It should be good enough to just submit asynchronous superblock writ= e-out. > Well, it happens for every inode being truncated / deleted to it can be > rather frequent. That's why I wanted to have now =3D=3D 1 case everywhere= - > i.e. just recompute the checksum and do mark_buffer_dirty(). I'd just > remove the 'now' test in this patch and then in patch 5 remove the now > argument from the function and callers as you did. It looked logical to me to use 'ext4_commit_super()' always and remove 'now' and marking the buffer dirty directly. Just because I thought the speed difference should be nearly 0, and 'ext4_commit_super()' is doing some error checking. But you seem to suggest to do the opposite, and I do not understand why would that be better. So I dropped this change so far. I've sent v5 where I basically only changed the commit message in patch 3 and dropped patch 5. In patch 3 I've explicitly indicated that we'll do more checksum calculations, but I think this is OK acceptable. Thanks! --=20 Best Regards, Artem Bityutskiy --=-g8v1ShFN8TOJjY8zEqUL Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.12 (GNU/Linux) iQIcBAABAgAGBQJP/B1ZAAoJECmIfjd9wqK0TREP/1CdrYyy7/NnH/ymCVj78GVZ JNxTsZb5t1Pg9nPNksqbjyXgclsE/anvopAwif81XiMZVkFhI63sg5ona8p5rb7N L70B1mZ6KJT3OKNGYFa/Hku6/lCks2HcKM0UbYXMzYQqi7Mi3WtTTeHUxe3eo0O3 PE/T8wo7BA2pnPj+CJLELyPitnm671BlZERjb25JPOFoJ5PQNopyb5q11fADf+6a 2H03r7PzcQZ0emkRMNoIKX3MYseUEGmffbUjT0JwoPD8oG0qsGdxOoa0DoZ7R3QS hwyh2xtb/SN4qisZX+UFM9OaUGuSMCep6iCvuQES6/ggFU+gtA88MUCN/ODqVINv DYcV6iM3REjU0aMrAxk8xRn/5EzDyWs0dcopwjzzxN+jmN5vCXLmHN7MWfu2UkOt EOo2kQz4XwesnWfzO5Oab0fCOQz4O9EqtFUQCQE7H3rVZQX5yBrurRrP0EjDqNQh UoVgkaoUco2pD/8bN95XItUw7tnrcp3rudYjZZO6/bvyZFEXQPnM9qiN1uiel8jt /RMflJ+RFhNgXUPg1xPj5NFA7CMRRJXC+g1PHP4TtwtygR86a53t8vSFDa1Hd58A zYaynfsQWL4spGnIG8uKTbVv3KA6Et4WByx98JfbGeo4pv5WDhq1Mn9XvKIcvjM0 Q3fmwbDlp6zAE+RLMmIe =CcLr -----END PGP SIGNATURE----- --=-g8v1ShFN8TOJjY8zEqUL--