* [PATCH mptcp-next 0/2] mptcp: rx path refactor follow-ups
@ 2022-08-24 11:18 Paolo Abeni
2022-08-24 11:18 ` [PATCH mptcp-next 1/2] Squash-to: "mptcp: move msk input path under full msk socket lock" Paolo Abeni
2022-08-24 11:18 ` [PATCH mptcp-next 2/2] mptcp: never re-inject data on a single subflow Paolo Abeni
0 siblings, 2 replies; 5+ messages in thread
From: Paolo Abeni @ 2022-08-24 11:18 UTC (permalink / raw)
To: mptcp
A couple of fixes trying to address the self-tests failures
seen after the recent refactor.
Paolo Abeni (2):
Squash-to: "mptcp: move msk input path under full msk socket lock"
mptcp: never re-inject data on a single subflow
net/mptcp/protocol.c | 3 ++-
net/mptcp/sched.c | 4 ++++
2 files changed, 6 insertions(+), 1 deletion(-)
--
2.37.1
^ permalink raw reply [flat|nested] 5+ messages in thread
* [PATCH mptcp-next 1/2] Squash-to: "mptcp: move msk input path under full msk socket lock"
2022-08-24 11:18 [PATCH mptcp-next 0/2] mptcp: rx path refactor follow-ups Paolo Abeni
@ 2022-08-24 11:18 ` Paolo Abeni
2022-08-24 12:38 ` Paolo Abeni
2022-08-24 11:18 ` [PATCH mptcp-next 2/2] mptcp: never re-inject data on a single subflow Paolo Abeni
1 sibling, 1 reply; 5+ messages in thread
From: Paolo Abeni @ 2022-08-24 11:18 UTC (permalink / raw)
To: mptcp
whoops, I forgot to really test for pending data at release_cb time.
The above causes several recurring failures in the self-tests.
Note that this could affect badly the mptcp performance (as we now
really move relevant CPU time from the subflow rx path/ksoftirqd to
the user-space process), even if I haven't performed perf-tests yet
on top of this change.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
This should be placed just before: "mptcp: move RCVPRUNE event later"/
the last rx path refactor
---
net/mptcp/protocol.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 74699bd47edf..d47c19494023 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -3008,7 +3008,8 @@ void __mptcp_check_push(struct sock *sk, struct sock *ssk)
#define MPTCP_FLAGS_PROCESS_CTX_NEED (BIT(MPTCP_PUSH_PENDING) | \
BIT(MPTCP_RETRANSMIT) | \
- BIT(MPTCP_FLUSH_JOIN_LIST))
+ BIT(MPTCP_FLUSH_JOIN_LIST) | \
+ BIT(MPTCP_DEQUEUE))
/* processes deferred events and flush wmem */
static void mptcp_release_cb(struct sock *sk)
--
2.37.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* [PATCH mptcp-next 2/2] mptcp: never re-inject data on a single subflow
2022-08-24 11:18 [PATCH mptcp-next 0/2] mptcp: rx path refactor follow-ups Paolo Abeni
2022-08-24 11:18 ` [PATCH mptcp-next 1/2] Squash-to: "mptcp: move msk input path under full msk socket lock" Paolo Abeni
@ 2022-08-24 11:18 ` Paolo Abeni
2022-08-24 13:00 ` mptcp: never re-inject data on a single subflow: Tests Results MPTCP CI
1 sibling, 1 reply; 5+ messages in thread
From: Paolo Abeni @ 2022-08-24 11:18 UTC (permalink / raw)
To: mptcp
If the MPTCP-level data ack is delayed WRT to the TCP-level ack,
there is a single subflow and the user-space stops pushing data,
the MPTCP-level retransmit may trigger in, fooling (disallowing)
infinite mapping fallback.
All the above is triggered quite reliably by the self-tests, once
we move the MPTCP receive path under the msk socket lock - delaying
the MPTCP-level acks.
Plain TCP is good enough to handle retransmissions as needed.
Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
Note that there are a couple of sad untold stories here. The first one
is as follow: with the delayed mptcp-level ack, at MPC handshake time we have:
MPC + SYN ->
<- MPC + SYN_ACK(1)
MPC + ACK(1) ->
<- DSS(n bytes) + ACK(1)
DSS_ACK(1) + ACK(n+1)
and no more acks from the client side, even after reading the
incoming n bytes data. So a possible alternative solution would be
to tweek mptcp_cleanup_rbuf() to properly handle this scenario.
Additionally, possibly, still due to the mptcp-level delyated ack,
we could need to tweek mptcp_cleanup_rbuf() more - e.g. do we need
to force mptcp-level ack when there is a large enough amount of newly
"ackable" data due to __mptcp_move_skbs() action? I don't know.
I guess/hope that the condition on mptcp-level window update already
implemented in mptcp_cleanup_rbuf() should also cover for the above,
but I'm not sure.
The other point is that I can't recall the previous discussion about
avoiding re-injection with a single subflow. I now think that is bad,
at least with delayed mptcp-level ack, and I don't see a need for that,
but possibly/likely I'm forgetting something?!?
---
net/mptcp/sched.c | 4 ++++
1 file changed, 4 insertions(+)
diff --git a/net/mptcp/sched.c b/net/mptcp/sched.c
index 044c5ec8bbfb..409e832085c2 100644
--- a/net/mptcp/sched.c
+++ b/net/mptcp/sched.c
@@ -162,6 +162,10 @@ struct sock *mptcp_sched_get_retrans(struct mptcp_sock *msk)
if (__mptcp_check_fallback(msk))
return NULL;
+ /* never retransmit when there is a single subflow */
+ if (list_is_singular(&msk->conn_list) && list_empty(&msk->join_list))
+ return NULL;
+
if (!msk->sched)
return mptcp_subflow_get_retrans(msk);
--
2.37.1
^ permalink raw reply related [flat|nested] 5+ messages in thread
* Re: [PATCH mptcp-next 1/2] Squash-to: "mptcp: move msk input path under full msk socket lock"
2022-08-24 11:18 ` [PATCH mptcp-next 1/2] Squash-to: "mptcp: move msk input path under full msk socket lock" Paolo Abeni
@ 2022-08-24 12:38 ` Paolo Abeni
0 siblings, 0 replies; 5+ messages in thread
From: Paolo Abeni @ 2022-08-24 12:38 UTC (permalink / raw)
To: mptcp
On Wed, 2022-08-24 at 13:18 +0200, Paolo Abeni wrote:
> whoops, I forgot to really test for pending data at release_cb time.
>
> The above causes several recurring failures in the self-tests.
>
> Note that this could affect badly the mptcp performance (as we now
> really move relevant CPU time from the subflow rx path/ksoftirqd to
> the user-space process), even if I haven't performed perf-tests yet
> on top of this change.
The first raw number are quite discouraging :/
-30% on single subflow test.
/P
^ permalink raw reply [flat|nested] 5+ messages in thread
* Re: mptcp: never re-inject data on a single subflow: Tests Results
2022-08-24 11:18 ` [PATCH mptcp-next 2/2] mptcp: never re-inject data on a single subflow Paolo Abeni
@ 2022-08-24 13:00 ` MPTCP CI
0 siblings, 0 replies; 5+ messages in thread
From: MPTCP CI @ 2022-08-24 13:00 UTC (permalink / raw)
To: Paolo Abeni; +Cc: mptcp
Hi Paolo,
Thank you for your modifications, that's great!
Our CI did some validations and here is its report:
- KVM Validation: normal:
- Unstable: 2 failed test(s): selftest_mptcp_join selftest_simult_flows 🔴:
- Task: https://cirrus-ci.com/task/4563343720579072
- Summary: https://api.cirrus-ci.com/v1/artifact/task/4563343720579072/summary/summary.txt
- KVM Validation: debug:
- Unstable: 2 failed test(s): selftest_mptcp_connect selftest_mptcp_join 🔴:
- Task: https://cirrus-ci.com/task/5689243627421696
- Summary: https://api.cirrus-ci.com/v1/artifact/task/5689243627421696/summary/summary.txt
Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/a85c4255a43d
If there are some issues, you can reproduce them using the same environment as
the one used by the CI thanks to a docker image, e.g.:
$ cd [kernel source code]
$ docker run -v "${PWD}:${PWD}:rw" -w "${PWD}" --privileged --rm -it \
--pull always mptcp/mptcp-upstream-virtme-docker:latest \
auto-debug
For more details:
https://github.com/multipath-tcp/mptcp-upstream-virtme-docker
Please note that despite all the efforts that have been already done to have a
stable tests suite when executed on a public CI like here, it is possible some
reported issues are not due to your modifications. Still, do not hesitate to
help us improve that ;-)
Cheers,
MPTCP GH Action bot
Bot operated by Matthieu Baerts (Tessares)
^ permalink raw reply [flat|nested] 5+ messages in thread
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2022-08-24 11:18 [PATCH mptcp-next 0/2] mptcp: rx path refactor follow-ups Paolo Abeni
2022-08-24 11:18 ` [PATCH mptcp-next 1/2] Squash-to: "mptcp: move msk input path under full msk socket lock" Paolo Abeni
2022-08-24 12:38 ` Paolo Abeni
2022-08-24 11:18 ` [PATCH mptcp-next 2/2] mptcp: never re-inject data on a single subflow Paolo Abeni
2022-08-24 13:00 ` mptcp: never re-inject data on a single subflow: Tests Results MPTCP CI
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