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Re: CD sizes again (and BoF reminder!)

On Sat, Jul 21, 2012 at 09:25:50PM +0300, Uoti Urpala wrote:
> Most of the time taken by cdebootstrap is wasted by dpkg on doing
> useless file syncs:
> cdebootstrap --arch=amd64 unstable debian-tree/
> from local package cache on ext4: 138 seconds
> on tmpfs where dpkg can't waste time on useless syncs: 21 seconds (and a
> significant portion of that is used by package scripts with "sleep 1")
> So at least in this case the biggest performance problem by far is the
> inappropriate use of fsync() or other disk synchronization primitives,
> and CPU use for unpacking is pretty much irrelevant.

My understanding is that dpkg uses fsync properly; that is, to guarantee
the data is on the disk before exiting or doing things that require that
data to be present.  I don't currently see any bugs on dpkg that
indicate that it is calling fsync needlessly or wastefully.  If you see
that behavior, could you please file a bug on dpkg?

brian m. carlson / brian with sandals: Houston, Texas, US
+1 832 623 2791 | http://www.crustytoothpaste.net/~bmc | My opinion only
OpenPGP: RSA v4 4096b: 88AC E9B2 9196 305B A994 7552 F1BA 225C 0223 B187

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