From: "Július Milan" <julius.milan.22@gmail.com>
To: xdp-newbies@vger.kernel.org
Subject: thread safe, lock free AF_XDP setup
Date: Mon, 10 Jul 2023 15:43:13 +0200 [thread overview]
Message-ID: <CANaGk7uNc171gmxH=NspPokePc+4eg2qg+jK+kVispnJcwRinA@mail.gmail.com> (raw)
Hi all
I am missing a full understanding of what really is thread safe and
what is not, when using AF_XDP.
RX and TX operations look obvious as every xsk socket has its own RX
and TX rings and so I can have multiple threads, as long as they don't
try to use the same ring of the same socket concurrently, that's the
only limitation (Am I correct yet?). So I can have for example 1:1
mapping of thread to xsk socket to avoid locking.
However what about UMEM rings, i.e. Completion and Fill queue?
About ring operations as __peek, __reserve ..., it is written (for ex.
here: https://www.kernel.org/doc/html/latest/networking/af_xdp.html#rings),
that they are not thread safe.
So it seems that I should use mutex to access them.
But I can see in:
https://github.com/xdp-project/bpf-examples/blob/master/AF_XDP-forwarding/xsk_fwd.c#L526
That they are filled / drained without locking, how is it then?
Does it make a difference if the socket is created by
xsk_socket__create_shared or xsk_socket__create?
What is the limitation that cannot be broken, as I described it for RX
/ TX? (if correctly)
Best Regards
Julius
next reply other threads:[~2023-07-10 13:43 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-07-10 13:43 Július Milan [this message]
2023-07-10 13:57 ` thread safe, lock free AF_XDP setup Magnus Karlsson
2023-07-10 14:39 ` Július Milan
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