Messages in this thread | | | From | Paul Menage <> | Date | Mon, 25 Jul 2011 18:05:00 -0700 | Subject | Re: [PATCH 6/7] cgroups: Add res counter common ancestor searching |
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On Mon, Jul 11, 2011 at 7:15 AM, Frederic Weisbecker <fweisbec@gmail.com> wrote: > Add a new API to find the common ancestor between two resource > counters. This includes the passed resource counter themselves. > > Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com>
Acked-by: Paul Menage <menage@google.com>
There's something distasteful about doing an O(N^2) search on every charge/uncharge operation, but I guess in general N isn't going to be more than 2 or 3 so it's not worth optimizing.
If you wanted to avoid the N^2 search then you could add a "depth" field in struct res_counter, which would be initialized to parent->depth+1, and then easily get both r1 and r2 to the same depth before proceeding up the tree in lock step, but that would bloat all instances of res_counter, which might work out as more expensive in the long run.
Paul
> Cc: Paul Menage <menage@google.com> > Cc: Li Zefan <lizf@cn.fujitsu.com> > Cc: Johannes Weiner <hannes@cmpxchg.org> > Cc: Aditya Kali <adityakali@google.com> > --- > include/linux/res_counter.h | 2 ++ > kernel/res_counter.c | 19 +++++++++++++++++++ > 2 files changed, 21 insertions(+), 0 deletions(-) > > diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h > index 8c421ac..354ed30 100644 > --- a/include/linux/res_counter.h > +++ b/include/linux/res_counter.h > @@ -139,6 +139,8 @@ void res_counter_uncharge_until(struct res_counter *counter, struct res_counter > unsigned long val); > void res_counter_uncharge(struct res_counter *counter, unsigned long val); > > +struct res_counter *res_counter_common_ancestor(struct res_counter *l, struct res_counter *r); > + > /** > * res_counter_margin - calculate chargeable space of a counter > * @cnt: the counter > diff --git a/kernel/res_counter.c b/kernel/res_counter.c > index 39f2513..1b2efd6 100644 > --- a/kernel/res_counter.c > +++ b/kernel/res_counter.c > @@ -102,6 +102,25 @@ void res_counter_uncharge(struct res_counter *counter, unsigned long val) > res_counter_uncharge_until(counter, NULL, val); > } > > +struct res_counter * > +res_counter_common_ancestor(struct res_counter *r1, struct res_counter *r2) > +{ > + struct res_counter *iter; > + > + while (r1) { > + iter = r2; > + while (iter) { > + if (iter == r1) > + return iter; > + iter = iter->parent; > + } > + > + r1 = r1->parent; > + } > + > + return NULL; > +} > + > static inline unsigned long long * > res_counter_member(struct res_counter *counter, int member) > { > -- > 1.7.5.4 > > -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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