On Fri, Jun 2, 2023 at 10:42 PM Shakeel Butt <shakeelb@xxxxxxxxxx> wrote: > > On Fri, Jun 02, 2023 at 04:11:34PM +0800, Abel Wu wrote: > > The sk_under_memory_pressure() is called to check whether there is > > memory pressure related to this socket. But now it ignores the net- > > memcg's pressure if the proto of the socket doesn't care about the > > global pressure, which may put burden on its memcg compaction or > > reclaim path (also remember that socket memory is un-reclaimable). > > > > So always check the memcg's vm status to alleviate memstalls when > > it's in pressure. > > > > This is interesting. UDP is the only protocol which supports memory > accounting (i.e. udp_memory_allocated) but it does not define > memory_pressure. In addition, it does have sysctl_udp_mem. So > effectively UDP supports a hard limit and ignores memcg pressure at the > moment. This patch will change its behavior to consider memcg pressure > as well. I don't have any objection but let's get opinion of UDP > maintainer. Others have more experience with memory pressure on UDP, for the record. Paolo worked on UDP memory pressure in https://lore.kernel.org/netdev/cover.1579281705.git.pabeni@xxxxxxxxxx/ It does seem odd to me to modify sk_under_memory_pressure only. See for instance its use in __sk_mem_raise_allocated: if (sk_has_memory_pressure(sk)) { u64 alloc; if (!sk_under_memory_pressure(sk)) return 1; This is not even reached as sk_has_memory_pressure is false for UDP. So this commit only affects the only other protocol-independent caller, __sk_mem_reduce_allocated, to possibly call sk_leave_memory_pressure if now under the global limit. What is the expected behavioral change in practice of this commit? > > Signed-off-by: Abel Wu <wuyun.abel@xxxxxxxxxxxxx> > > --- > > include/net/sock.h | 6 ++---- > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/include/net/sock.h b/include/net/sock.h > > index 3f63253ee092..ad1895ffbc4a 100644 > > --- a/include/net/sock.h > > +++ b/include/net/sock.h > > @@ -1411,13 +1411,11 @@ static inline bool sk_has_memory_pressure(const struct sock *sk) > > > > static inline bool sk_under_memory_pressure(const struct sock *sk) > > { > > - if (!sk->sk_prot->memory_pressure) > > - return false; > > - > > if (mem_cgroup_under_socket_pressure(sk->sk_memcg)) > > return true; > > > > - return !!*sk->sk_prot->memory_pressure; > > + return sk->sk_prot->memory_pressure && > > + *sk->sk_prot->memory_pressure; > > } > > > > static inline long > > -- > > 2.37.3 > >
