make cleanworld

[Alexander Best]

On Tue Nov  8 11, Dimitry Andric wrote:
> On 2011-11-08 21:49, Alexander Best wrote:
> > any reason 'make cleanworld' does
> > 
> > otaku% make cleanworld
> > rm -rf /usr/obj/usr/git-freebsd-head/*
> > chflags -R 0 /usr/obj/usr/git-freebsd-head
> > rm -rf /usr/obj/usr/git-freebsd-head/*
> > 
> > where
> > 
> > otaku% make cleanworld
> > chflags -R 0 /usr/obj/usr/git-freebsd-head
> > rm -rf /usr/obj/usr/git-freebsd-head/*
> > 
> > should be sufficient?
> 
> The first method is more efficient, because there are usually just a few
> files with schg flags set on them (zero even, if you build as a regular
> user).
> 
> Suppose you have 30,000 files in /usr/obj, of which 20 have schg flags.
> 
> The first method will unlink 29,980 files, failing on 20 of them.  Then
> it will change flags on just 20 files, and lastly unlink those 20 files.
> Total number of 'operations' is 30,000 + 20 + 20 = 30,040.
> 
> The second method will change flags on all 30,000 files, then unlink all
> 30,000 files.  Total number of 'operations' is now 30,000 + 30,000 =
> 60,000.

maybe the comment in /usr/src/Makefile could be updated to mention the
efficiency aspect? right now it only says:

#
# This 'cleanworld' target is not included in TGTS, because it is not a
# recursive target.  All of the work for it is done right here.   It is
# expected that BW_CANONICALOBJDIR == the CANONICALOBJDIR as would be
# created by bsd.obj.mk, except that we don't want to .include that file
# in this makefile.
# 
# In the following, the first 'rm' in a series will usually remove all
# files and directories.  If it does not, then there are probably some
# files with chflags set, so this unsets them and tries the 'rm' a
# second time.  There are situations where this target will be cleaning
# some directories via more than one method, but that duplication is
# needed to correctly handle all the possible situations. Also this
# 

another tought would be to do the following:

find -flags +XXX /usr/obj/usr/git-freebsd-head -exec chflags -R 0 {} +
rm/obj/usr/git-freebsd-head/*

that should only execute chflags(1) on those files with flags set.

cheers.
alex