On Wed, Jan 18, 2012 at 07:15:58PM +0400, Glauber Costa wrote: > There is a case in __sk_mem_schedule(), where an allocation > is beyond the maximum, but yet we are allowed to proceed. > It happens under the following condition: > > sk->sk_wmem_queued + size >= sk->sk_sndbuf > > The network code won't revert the allocation in this case, > meaning that at some point later it'll try to do it. Since > this is never communicated to the underlying res_counter > code, there is an inbalance in res_counter uncharge operation. > > I see two ways of fixing this: > > 1) storing the information about those allocations somewhere > in memcg, and then deducting from that first, before > we start draining the res_counter, > 2) providing a slightly different allocation function for > the res_counter, that matches the original behavior of > the network code more closely. > > I decided to go for #2 here, believing it to be more elegant, > since #1 would require us to do basically that, but in a more > obscure way. > > I will eventually submit it through Dave for the -net tree, > but I wanted to query you guys first, to see if this approach > is acceptable or if you'd prefer me to try something else. > > Thanks > > Signed-off-by: Glauber Costa <glommer@xxxxxxxxxxxxx> > Cc: KAMEZAWA Hiroyuki <kamezawa.hiroyu@xxxxxxxxxxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxx> > --- > include/linux/res_counter.h | 6 ++++++ > include/net/sock.h | 10 ++++------ > kernel/res_counter.c | 25 +++++++++++++++++++++++++ > net/core/sock.c | 4 ++-- > 4 files changed, 37 insertions(+), 8 deletions(-) > > diff --git a/include/linux/res_counter.h b/include/linux/res_counter.h > index c9d625c..32a7b02 100644 > --- a/include/linux/res_counter.h > +++ b/include/linux/res_counter.h > @@ -109,12 +109,18 @@ void res_counter_init(struct res_counter *counter, struct res_counter *parent); > * > * returns 0 on success and <0 if the counter->usage will exceed the > * counter->limit _locked call expects the counter->lock to be taken > + * > + * charge_nofail works the same, except that it charges the resource > + * counter unconditionally, and returns < 0 if the after the current > + * charge we are over limit. > */ res_counter_margin() assumes usage <= limit is always true. Just make sure you return 0 if that is not the case, or the charge path can get confused, thinking there is enough room and retry needlessly. Otherwise, looks good. -- To unsubscribe from this list: send the line "unsubscribe cgroups" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
