Dear kernel team, On Mon, Nov 15, 2010 at 09:58:47AM +0100, Sven Joachim wrote: > > I'm sorry, I won't have the time to do new benchmarks on this. > > > > The only benchmarks we have have been made by Sven Joachim: > > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=578635#20 > > (asyncsync is the switch to sync() instead of fsync() so the opposite of > > the above patch) > > > > He mentionned that without the sync() trick it takes 3 to 5 times longer > > to unpack a package. > > Even longer actually, see the figures below. > > > Sven, would you have time to provide some of the stats asked by the > > release team? > > I can only test ext4, here are some samples of dpkg unpacking a large > package (dpkg --unpack --no-triggers emacs23-common_23.2+1-5.1_all.deb), > leaving out user and sys times since those do not vary much (~ 0.5 > seconds in every case): > > dpkg version Cache mount options unpack time > ̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅̅ > 1.15.8.5 cold defaults 7.803s > 1.15.8.5 warm defaults 5.283s > 1.15.8.5 cold nodelalloc 7.608s > 1.15.8.5 warm nodelalloc 3.783s > 1.15.7 cold defaults 40.429s > 1.15.7 warm defaults 37.848s > 1.15.7 cold nodelalloc 7.945s > 1.15.7 warm nodelalloc 3.524s > > All this is with a standard squeeze kernel on an otherwise idle system. > It should be noted that with lots of other disk activity such as writing > to USB disks, the figures in dpkg 1.15.8.5 can become much worse and > dpkg might even stall because of the many sync() calls: > http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=595927. > > As far as ext4 is concerned, switching back to fsync() seems to be > acceptable only if the filesystem is mounted with the nodelalloc > option. Maybe the installer should set this up.
and I don't suppose we could make that the default? Is there anything else the dpkg developers can try to be portable and still not be sacrificing performance? Kind regards Philipp Kern
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