Hi! [ Context for people CCed, this is a bug report against dpkg due to it recently starting to use deferred fsync()+rename() and introducing a major performance degradation on ext4. I've taken the liberty to add people previously involved in the btrfs dpkg bug report. ]
On Tue, 2010-05-11 at 10:59:51 +0200, Raphael Hertzog wrote: > On Wed, 21 Apr 2010, Sven Joachim wrote: > > The fix for #577756 reintroduced a severe performance degradation first > > reported in [1]. On my system, unpacking the emacs23-common package > > with a warm cache takes ~ 40 seconds, about seven times as long as with > > 1.15.5.6 and 1.15.6.1. > Can you try with the dpkg version that is in the branch pu/async-sync > of git://git.hadrons.org/git/debian/dpkg.git ? The relevant patch is <http://git.hadrons.org/?p=debian/dpkg/dpkg.git;a=commitdiff;h=b405384c>, which on Linux switches from using an fsync() per file to a global sync() per package. This seems to help quite a bit with ext4, as reported by few people who have done some tests. > It would be nice to have a quick answer so that we can decide if we can > push that change in 1.15.7.2. I just happened to read <http://lwn.net/Articles/358940/>, and was wondering if this would affect badly on btrfs (by being slower with sync() than fsync()), so it would be nice to see some tests w/ the patch using the pu/async-sync branch, and w/o using dpkg 1.15.7, 1.15.7.1 or the sid branch. And probably by doing some parallel I/O to see the effect of sync(). To build on a Debian based system, you just need to “autoreconf -f -i” and then “debuild -us -uc -b”. If pre-built packages would make this easier I can prepare some for requested architectures. If you are using Ubuntu, Colin Watson has prepared packages on his PPA <https://launchpad.net/~cjwatson/+archive/ppa> with the patch. thanks, guillem -- To UNSUBSCRIBE, email to debian-bugs-dist-requ...@lists.debian.org with a subject of "unsubscribe". Trouble? Contact listmas...@lists.debian.org
