Messages in this thread | | | Date | Wed, 13 Jan 2010 15:28:01 +0100 | From | Frederic Weisbecker <> | Subject | Re: [PATCH 1/3] rbtree: Introduce rb_for_each_entry |
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On Wed, Jan 13, 2010 at 03:18:16PM +0100, Peter Zijlstra wrote: > On Wed, 2010-01-13 at 12:13 -0200, Arnaldo Carvalho de Melo wrote: > > Em Wed, Jan 13, 2010 at 02:58:53PM +0100, Peter Zijlstra escreveu: > > > On Wed, 2010-01-13 at 11:52 -0200, Arnaldo Carvalho de Melo wrote: > > > > Em Wed, Jan 13, 2010 at 02:34:45PM +0100, Frederic Weisbecker escreveu: > > > > > At least it matches many patterns in perf :) > > > > > > > > What an insane piece of... software! 8-) Whatever, if it makes Peter > > > > happy we can keep it on tools/perf/util/include/linux/rbtree.h, just > > > > after the: > > > > > > > > #include "../../../../include/linux/rbtree.h" > > > > > > > > ;-) > > > > > > > > Just like we have list_del_range() in tools/perf/util/include/linux/list.h. > > > > > > That's not the point, doing a for_each on the rb-trees as we have today > > > is a O(n log(n)) operation, not something you should want to do often. > > > > > > Adding a helper promotes the idea that its a sane thing to do, its not. > > > > > > If you really need it, open coding it isn't hard, but the lack of helper > > > does make you think and hopefully realize you're doing something funny. > > > > We need it in several places in the perf tools, to present sorted results, to > > dump the maps for debugging purposes, etc. > > > > But I'll go and look at each one of them to see if there is any where it > > is used in some stupid way. > > Sure, but again, that's missing the point, adding that helper isn't a > good thing. We have no 64bit division operators in Linux either, for the > very same reason. >
I don't understand why this is unsane. Sure it is O(n log(n)), but that's what is suitable for our use in perf. Shouldn't we simplify it through a helper just because it's not something sane in most other cases?
But yeah, such helper inside the kernel wouldn't be sane, as it wouldn't fit any sane need I guess.
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