Re: [PATCH net-next v5 2/3] sock: Always take memcg pressure into consideration
From: Shakeel Butt <hidden>
Date: 2023-06-02 20:42:07
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+Willem 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.
quoted hunk ↗ jump to hunk
Signed-off-by: Abel Wu <redacted> --- 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