From: Johannes Weiner <hannes@xxxxxxxxxxx> Date: Tue, 24 Nov 2015 16:51:59 -0500 > There won't be a tcp control soft limit, so integrating the memcg code > into the global skmem limiting scheme complicates things > unnecessarily. Replace this with simple and clear charge and uncharge > calls--hidden behind a jump label--to account skb memory. > > Note that this is not purely aesthetic: as a result of shoehorning the > per-memcg code into the same memory accounting functions that handle > the global level, the old code would compare the per-memcg consumption > against the smaller of the per-memcg limit and the global limit. This > allowed the total consumption of multiple sockets to exceed the global > limit, as long as the individual sockets stayed within bounds. After > this change, the code will always compare the per-memcg consumption to > the per-memcg limit, and the global consumption to the global limit, > and thus close this loophole. > > Without a soft limit, the per-memcg memory pressure state in sockets > is generally questionable. However, we did it until now, so we > continue to enter it when the hard limit is hit, and packets are > dropped, to let other sockets in the cgroup know that they shouldn't > grow their transmit windows, either. However, keep it simple in the > new callback model and leave memory pressure lazily when the next > packet is accepted (as opposed to doing it synchroneously when packets > are processed). When packets are dropped, network performance will > already be in the toilet, so that should be a reasonable trade-off. > > As described above, consumption is now checked on the per-memcg level > and the global level separately. Likewise, memory pressure states are > maintained on both the per-memcg level and the global level, and a > socket is considered under pressure when either level asserts as much. > > Signed-off-by: Johannes Weiner <hannes@xxxxxxxxxxx> > Reviewed-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx> Acked-by: David S. Miller <davem@xxxxxxxxxxxxx> -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>