> On Jul 18, 2023, at 00:46, Eric Dumazet <edumazet@xxxxxxxxxx> wrote: > > On Thu, Jul 13, 2023 at 1:24 PM <menglong8.dong@xxxxxxxxx> wrote: >> >> From: Menglong Dong <imagedong@xxxxxxxxxxx> >> >> For now, skb will be dropped directly if rmem schedule fails, which means >> tcp_try_rmem_schedule() returns an error. This can happen on following >> cases: >> >> 1. The total memory allocated for TCP protocol is up to tcp_mem[2], and >> the receive queue of the tcp socket is not empty. >> 2. The receive buffer of the tcp socket is full, which can happen on small >> packet cases. >> >> If the user hangs and doesn't take away the packet in the receive queue >> with recv() or read() for a long time, the sender will keep >> retransmitting until timeout, and the tcp connection will break. >> >> In order to handle such case, we introduce the tcp protocol OOM detection >> in following steps, as Neal Cardwell suggested: >> > > For the record, I dislike this patch. I am not sure what Neal had in mind. > > I suggested instead to send an ACK RWIN 0, whenever we were under > extreme memory pressure, > and we only could queue one skb in the receive queue. > > For details, look at the points we call sk_forced_mem_schedule(). > This would be a matter of refactoring code around it, in tcp_data_queue() > > The patch would be much simpler. Nothing changed at the sender side :/ I think you are right. I misunderstood the code in tcp_retransmit_timer(). It seems that it already handle the window shrink case properly. Let me do more testing first. Thanks! Menglong Dong
