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Re: Pre-approval request for dpkg sync() changes for squeeze


On Wed, 10 Nov 2010, Philipp Kern wrote:
> On Tue, Nov 09, 2010 at 07:50:23PM +0100, Philipp Kern wrote:
> > On Fri, Oct 22, 2010 at 11:35:54AM +0200, Guillem Jover wrote:
> > >   1) Switch back from sync() to fsync() before rename() (while keeping
> > >      the sync() code around for the benefit of other distributions
> > >      that might not want to switch just yet). So to avoid unrelated
> > >      I/O when there's background work being done for example. This
> > >      hack also only works on Linux where sync() is synchronous, so
> > >      it would unify that code path for all dpkg supported platforms.
> > > 
> > >      Bug: #588339
> > > 
> > >   <http://git.hadrons.org/?p=debian/dpkg/dpkg.git;a=commitdiff;h=87740373>
> > I'm still not sure we have all needed information.  Would you mind doing
> > a matrix what this change would cause?  I.e. if we get performance
> > regressions on ext4, btrfs or even ext3 with the squeeze kernel (we're
> > really only interested in that one, not some random other revision)
> > or if we even get data safety regressions.
> I also forgot to throw nfs into the picture.

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:
(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.

Sven, would you have time to provide some of the stats asked by the
release team?

We really need to upload dpkg this week so we must take a decision what
goes in.

Raphaël Hertzog ◈ Debian Developer ◈ [Flattr=20693]

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