To support redundant package schedulers more easily, this patch refactors
__mptcp_push_pending() logic from:
For each dfrag:
While sends succeed:
Call the scheduler (selects subflow and msk->snd_burst)
Update subflow locks (push/release/acquire as needed)
Send the dfrag data with mptcp_sendmsg_frag()
Update already_sent, snd_nxt, snd_burst
Update msk->first_pending
Push/release on final subflow
->
While the scheduler selects one subflow:
Lock the subflow
For each pending dfrag:
While sends succeed:
Send the dfrag data with mptcp_sendmsg_frag()
Update already_sent, snd_nxt, snd_burst
Update msk->first_pending
Break if required by msk->snd_burst / etc
Push and release the subflow
Refactors __mptcp_subflow_push_pending logic from:
For each dfrag:
While sends succeed:
Call the scheduler (selects subflow and msk->snd_burst)
Send the dfrag data with mptcp_subflow_delegate(), break
Send the dfrag data with mptcp_sendmsg_frag()
Update dfrag->already_sent, msk->snd_nxt, msk->snd_burst
Update msk->first_pending
->
While first_pending isn't empty:
Call the scheduler (selects subflow and msk->snd_burst)
Send the dfrag data with mptcp_subflow_delegate(), break
Send the dfrag data with mptcp_sendmsg_frag()
For each pending dfrag:
While sends succeed:
Send the dfrag data with mptcp_sendmsg_frag()
Update already_sent, snd_nxt, snd_burst
Update msk->first_pending
Break if required by msk->snd_burst / etc
Move the duplicate code from __mptcp_push_pending() and
__mptcp_subflow_push_pending() into a new helper function, named
__subflow_push_pending(). Simplify __mptcp_push_pending() and
__mptcp_subflow_push_pending() by invoking this helper.
Also move the burst check conditions out of the function
mptcp_subflow_get_send(), check them in __mptcp_push_pending() and
__mptcp_subflow_push_pending() in the inner "for each pending dfrag"
loop.
Signed-off-by: Geliang Tang <geliang.tang@suse.com>
---
net/mptcp/protocol.c | 155 +++++++++++++++++++------------------------
1 file changed, 70 insertions(+), 85 deletions(-)
diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index ddeb8b36a677..9b73297f6543 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -1417,14 +1417,6 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
u64 linger_time;
long tout = 0;
- /* re-use last subflow, if the burst allow that */
- if (msk->last_snd && msk->snd_burst > 0 &&
- sk_stream_memory_free(msk->last_snd) &&
- mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd))) {
- mptcp_set_timeout(sk);
- return msk->last_snd;
- }
-
/* pick the subflow with the lower wmem/wspace ratio */
for (i = 0; i < SSK_MODE_MAX; ++i) {
send_info[i].ssk = NULL;
@@ -1491,12 +1483,6 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
return ssk;
}
-static void mptcp_push_release(struct sock *ssk, struct mptcp_sendmsg_info *info)
-{
- tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle, info->size_goal);
- release_sock(ssk);
-}
-
static void mptcp_update_post_push(struct mptcp_sock *msk,
struct mptcp_data_frag *dfrag,
u32 sent)
@@ -1528,68 +1514,80 @@ void mptcp_check_and_set_pending(struct sock *sk)
mptcp_sk(sk)->push_pending |= BIT(MPTCP_PUSH_PENDING);
}
-void __mptcp_push_pending(struct sock *sk, unsigned int flags)
+static int __subflow_push_pending(struct sock *sk, struct sock *ssk,
+ struct mptcp_sendmsg_info *info)
{
- struct sock *prev_ssk = NULL, *ssk = NULL;
struct mptcp_sock *msk = mptcp_sk(sk);
- struct mptcp_sendmsg_info info = {
- .flags = flags,
- };
- bool do_check_data_fin = false;
struct mptcp_data_frag *dfrag;
- int len;
+ int len, copied = 0, err = 0;
while ((dfrag = mptcp_send_head(sk))) {
- info.sent = dfrag->already_sent;
- info.limit = dfrag->data_len;
+ info->sent = dfrag->already_sent;
+ info->limit = dfrag->data_len;
len = dfrag->data_len - dfrag->already_sent;
while (len > 0) {
int ret = 0;
- prev_ssk = ssk;
- ssk = mptcp_subflow_get_send(msk);
-
- /* First check. If the ssk has changed since
- * the last round, release prev_ssk
- */
- if (ssk != prev_ssk && prev_ssk)
- mptcp_push_release(prev_ssk, &info);
- if (!ssk)
- goto out;
-
- /* Need to lock the new subflow only if different
- * from the previous one, otherwise we are still
- * helding the relevant lock
- */
- if (ssk != prev_ssk)
- lock_sock(ssk);
-
- ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
+ ret = mptcp_sendmsg_frag(sk, ssk, dfrag, info);
if (ret <= 0) {
- if (ret == -EAGAIN)
- continue;
- mptcp_push_release(ssk, &info);
+ err = copied ? : ret;
goto out;
}
- do_check_data_fin = true;
- info.sent += ret;
+ info->sent += ret;
+ copied += ret;
len -= ret;
mptcp_update_post_push(msk, dfrag, ret);
}
WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
+
+ if (msk->snd_burst <= 0 ||
+ !sk_stream_memory_free(ssk) ||
+ !mptcp_subflow_active(mptcp_subflow_ctx(ssk))) {
+ err = copied ? : -EAGAIN;
+ goto out;
+ }
+ mptcp_set_timeout(sk);
+ }
+ err = copied;
+
+out:
+ if (copied) {
+ tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle,
+ info->size_goal);
}
- /* at this point we held the socket lock for the last subflow we used */
- if (ssk)
- mptcp_push_release(ssk, &info);
+ return err;
+}
+
+void __mptcp_push_pending(struct sock *sk, unsigned int flags)
+{
+ struct mptcp_sock *msk = mptcp_sk(sk);
+ struct mptcp_sendmsg_info info = {
+ .flags = flags,
+ };
+ struct sock *ssk;
+ int ret = 0;
+
+again:
+ while (mptcp_send_head(sk) && (ssk = mptcp_subflow_get_send(msk))) {
+ lock_sock(ssk);
+ ret = __subflow_push_pending(sk, ssk, &info);
+ release_sock(ssk);
+
+ if (ret <= 0) {
+ if (ret == -EAGAIN)
+ goto again;
+ goto out;
+ }
+ }
out:
/* ensure the rtx timer is running */
if (!mptcp_timer_pending(sk))
mptcp_reset_timer(sk);
- if (do_check_data_fin)
+ if (ret > 0)
__mptcp_check_send_data_fin(sk);
}
@@ -1599,51 +1597,38 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool
struct mptcp_sendmsg_info info = {
.data_lock_held = true,
};
- struct mptcp_data_frag *dfrag;
struct sock *xmit_ssk;
- int len, copied = 0;
+ int ret = 0;
info.flags = 0;
- while ((dfrag = mptcp_send_head(sk))) {
- info.sent = dfrag->already_sent;
- info.limit = dfrag->data_len;
- len = dfrag->data_len - dfrag->already_sent;
- while (len > 0) {
- int ret = 0;
-
- /* check for a different subflow usage only after
- * spooling the first chunk of data
- */
- xmit_ssk = first ? ssk : mptcp_subflow_get_send(msk);
- if (!xmit_ssk)
- goto out;
- if (xmit_ssk != ssk) {
- mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
- MPTCP_DELEGATE_SEND);
- goto out;
- }
-
- ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
- if (ret <= 0)
- goto out;
-
- info.sent += ret;
- copied += ret;
- len -= ret;
- first = false;
+again:
+ while (mptcp_send_head(sk)) {
+ /* check for a different subflow usage only after
+ * spooling the first chunk of data
+ */
+ xmit_ssk = first ? ssk : mptcp_subflow_get_send(msk);
+ if (!xmit_ssk)
+ goto out;
+ if (xmit_ssk != ssk) {
+ mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
+ MPTCP_DELEGATE_SEND);
+ goto out;
+ }
- mptcp_update_post_push(msk, dfrag, ret);
+ ret = __subflow_push_pending(sk, ssk, &info);
+ first = false;
+ if (ret <= 0) {
+ if (ret == -EAGAIN)
+ goto again;
+ break;
}
- WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
}
out:
/* __mptcp_alloc_tx_skb could have released some wmem and we are
* not going to flush it via release_sock()
*/
- if (copied) {
- tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
- info.size_goal);
+ if (ret > 0) {
if (!mptcp_timer_pending(sk))
mptcp_reset_timer(sk);
--
2.35.3On Tue, 18 Oct 2022, Geliang Tang wrote:
> To support redundant package schedulers more easily, this patch refactors
> __mptcp_push_pending() logic from:
>
> For each dfrag:
> While sends succeed:
> Call the scheduler (selects subflow and msk->snd_burst)
> Update subflow locks (push/release/acquire as needed)
> Send the dfrag data with mptcp_sendmsg_frag()
> Update already_sent, snd_nxt, snd_burst
> Update msk->first_pending
> Push/release on final subflow
>
> ->
>
> While the scheduler selects one subflow:
> Lock the subflow
> For each pending dfrag:
> While sends succeed:
> Send the dfrag data with mptcp_sendmsg_frag()
> Update already_sent, snd_nxt, snd_burst
> Update msk->first_pending
> Break if required by msk->snd_burst / etc
> Push and release the subflow
>
> Refactors __mptcp_subflow_push_pending logic from:
>
> For each dfrag:
> While sends succeed:
> Call the scheduler (selects subflow and msk->snd_burst)
> Send the dfrag data with mptcp_subflow_delegate(), break
> Send the dfrag data with mptcp_sendmsg_frag()
> Update dfrag->already_sent, msk->snd_nxt, msk->snd_burst
> Update msk->first_pending
>
> ->
>
> While first_pending isn't empty:
> Call the scheduler (selects subflow and msk->snd_burst)
> Send the dfrag data with mptcp_subflow_delegate(), break
> Send the dfrag data with mptcp_sendmsg_frag()
> For each pending dfrag:
> While sends succeed:
> Send the dfrag data with mptcp_sendmsg_frag()
> Update already_sent, snd_nxt, snd_burst
> Update msk->first_pending
> Break if required by msk->snd_burst / etc
>
> Move the duplicate code from __mptcp_push_pending() and
> __mptcp_subflow_push_pending() into a new helper function, named
> __subflow_push_pending(). Simplify __mptcp_push_pending() and
> __mptcp_subflow_push_pending() by invoking this helper.
>
> Also move the burst check conditions out of the function
> mptcp_subflow_get_send(), check them in __mptcp_push_pending() and
> __mptcp_subflow_push_pending() in the inner "for each pending dfrag"
> loop.
>
> Signed-off-by: Geliang Tang <geliang.tang@suse.com>
> ---
> net/mptcp/protocol.c | 155 +++++++++++++++++++------------------------
> 1 file changed, 70 insertions(+), 85 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index ddeb8b36a677..9b73297f6543 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -1417,14 +1417,6 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
> u64 linger_time;
> long tout = 0;
>
> - /* re-use last subflow, if the burst allow that */
> - if (msk->last_snd && msk->snd_burst > 0 &&
> - sk_stream_memory_free(msk->last_snd) &&
> - mptcp_subflow_active(mptcp_subflow_ctx(msk->last_snd))) {
> - mptcp_set_timeout(sk);
> - return msk->last_snd;
> - }
> -
> /* pick the subflow with the lower wmem/wspace ratio */
> for (i = 0; i < SSK_MODE_MAX; ++i) {
> send_info[i].ssk = NULL;
> @@ -1491,12 +1483,6 @@ struct sock *mptcp_subflow_get_send(struct mptcp_sock *msk)
> return ssk;
> }
>
> -static void mptcp_push_release(struct sock *ssk, struct mptcp_sendmsg_info *info)
> -{
> - tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle, info->size_goal);
> - release_sock(ssk);
> -}
> -
> static void mptcp_update_post_push(struct mptcp_sock *msk,
> struct mptcp_data_frag *dfrag,
> u32 sent)
> @@ -1528,68 +1514,80 @@ void mptcp_check_and_set_pending(struct sock *sk)
> mptcp_sk(sk)->push_pending |= BIT(MPTCP_PUSH_PENDING);
> }
>
> -void __mptcp_push_pending(struct sock *sk, unsigned int flags)
> +static int __subflow_push_pending(struct sock *sk, struct sock *ssk,
> + struct mptcp_sendmsg_info *info)
> {
> - struct sock *prev_ssk = NULL, *ssk = NULL;
> struct mptcp_sock *msk = mptcp_sk(sk);
> - struct mptcp_sendmsg_info info = {
> - .flags = flags,
> - };
> - bool do_check_data_fin = false;
> struct mptcp_data_frag *dfrag;
> - int len;
> + int len, copied = 0, err = 0;
>
> while ((dfrag = mptcp_send_head(sk))) {
> - info.sent = dfrag->already_sent;
> - info.limit = dfrag->data_len;
> + info->sent = dfrag->already_sent;
> + info->limit = dfrag->data_len;
> len = dfrag->data_len - dfrag->already_sent;
> while (len > 0) {
> int ret = 0;
>
> - prev_ssk = ssk;
> - ssk = mptcp_subflow_get_send(msk);
> -
> - /* First check. If the ssk has changed since
> - * the last round, release prev_ssk
> - */
> - if (ssk != prev_ssk && prev_ssk)
> - mptcp_push_release(prev_ssk, &info);
> - if (!ssk)
> - goto out;
> -
> - /* Need to lock the new subflow only if different
> - * from the previous one, otherwise we are still
> - * helding the relevant lock
> - */
> - if (ssk != prev_ssk)
> - lock_sock(ssk);
> -
> - ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
> + ret = mptcp_sendmsg_frag(sk, ssk, dfrag, info);
> if (ret <= 0) {
> - if (ret == -EAGAIN)
> - continue;
> - mptcp_push_release(ssk, &info);
> + err = copied ? : ret;
> goto out;
> }
>
> - do_check_data_fin = true;
> - info.sent += ret;
> + info->sent += ret;
> + copied += ret;
> len -= ret;
>
> mptcp_update_post_push(msk, dfrag, ret);
> }
> WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
> +
> + if (msk->snd_burst <= 0 ||
> + !sk_stream_memory_free(ssk) ||
> + !mptcp_subflow_active(mptcp_subflow_ctx(ssk))) {
> + err = copied ? : -EAGAIN;
> + goto out;
> + }
> + mptcp_set_timeout(sk);
> + }
> + err = copied;
> +
> +out:
> + if (copied) {
> + tcp_push(ssk, 0, info->mss_now, tcp_sk(ssk)->nonagle,
> + info->size_goal);
> }
>
> - /* at this point we held the socket lock for the last subflow we used */
> - if (ssk)
> - mptcp_push_release(ssk, &info);
> + return err;
> +}
> +
> +void __mptcp_push_pending(struct sock *sk, unsigned int flags)
> +{
> + struct mptcp_sock *msk = mptcp_sk(sk);
> + struct mptcp_sendmsg_info info = {
> + .flags = flags,
> + };
> + struct sock *ssk;
> + int ret = 0;
> +
> +again:
> + while (mptcp_send_head(sk) && (ssk = mptcp_subflow_get_send(msk))) {
> + lock_sock(ssk);
> + ret = __subflow_push_pending(sk, ssk, &info);
> + release_sock(ssk);
Thanks for reworking this patch set, it's easier to see what's going on
now.
With this refactoring a long send will push, release, and re-lock the
subflow for every "burst" (as limited by snd_burst or by the available
buffer space). That seems like it could add noticeable overhead for
high-throughput connections, compared to the old code that would defer the
push & unlock. In earlier reviews I didn't consider this carefully enough:
I thought that __subflow_push_pending() would usually be able to send all
the pending dfrags, but I didn't consider sendmsg calls with lots of data
(more than the burst size).
I think it's possible to keep the push/unlock optimization in
__mptcp_push_pending() if the tcp_push() is handled outside
__subflow_push_pending().
Would likely need more information returned from the helper to give the
caller of __subflow_push_pending() enough information, like:
static int __subflow_push_pending(struct sock *sk, struct sock *ssk,
struct mptcp_sendmsg_info *info,
bool *needs_push)
I'll talk to Paolo about this on Thursday too (and he's welcome to chime
in here :) )
> +
> + if (ret <= 0) {
> + if (ret == -EAGAIN)
> + goto again;
Better to use a 'continue' here.
> + goto out;
> + }
> + }
>
> out:
> /* ensure the rtx timer is running */
> if (!mptcp_timer_pending(sk))
> mptcp_reset_timer(sk);
> - if (do_check_data_fin)
> + if (ret > 0)
> __mptcp_check_send_data_fin(sk);
> }
>
> @@ -1599,51 +1597,38 @@ static void __mptcp_subflow_push_pending(struct sock *sk, struct sock *ssk, bool
> struct mptcp_sendmsg_info info = {
> .data_lock_held = true,
> };
> - struct mptcp_data_frag *dfrag;
> struct sock *xmit_ssk;
> - int len, copied = 0;
> + int ret = 0;
>
> info.flags = 0;
> - while ((dfrag = mptcp_send_head(sk))) {
> - info.sent = dfrag->already_sent;
> - info.limit = dfrag->data_len;
> - len = dfrag->data_len - dfrag->already_sent;
> - while (len > 0) {
> - int ret = 0;
> -
> - /* check for a different subflow usage only after
> - * spooling the first chunk of data
> - */
> - xmit_ssk = first ? ssk : mptcp_subflow_get_send(msk);
> - if (!xmit_ssk)
> - goto out;
> - if (xmit_ssk != ssk) {
> - mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
> - MPTCP_DELEGATE_SEND);
> - goto out;
> - }
> -
> - ret = mptcp_sendmsg_frag(sk, ssk, dfrag, &info);
> - if (ret <= 0)
> - goto out;
> -
> - info.sent += ret;
> - copied += ret;
> - len -= ret;
> - first = false;
> +again:
> + while (mptcp_send_head(sk)) {
> + /* check for a different subflow usage only after
> + * spooling the first chunk of data
> + */
> + xmit_ssk = first ? ssk : mptcp_subflow_get_send(msk);
> + if (!xmit_ssk)
> + goto out;
> + if (xmit_ssk != ssk) {
> + mptcp_subflow_delegate(mptcp_subflow_ctx(xmit_ssk),
> + MPTCP_DELEGATE_SEND);
> + goto out;
> + }
>
> - mptcp_update_post_push(msk, dfrag, ret);
> + ret = __subflow_push_pending(sk, ssk, &info);
> + first = false;
> + if (ret <= 0) {
> + if (ret == -EAGAIN)
> + goto again;
Another place to use 'continue'.
> + break;
> }
> - WRITE_ONCE(msk->first_pending, mptcp_send_next(sk));
> }
>
> out:
> /* __mptcp_alloc_tx_skb could have released some wmem and we are
> * not going to flush it via release_sock()
> */
> - if (copied) {
> - tcp_push(ssk, 0, info.mss_now, tcp_sk(ssk)->nonagle,
> - info.size_goal);
> + if (ret > 0) {
> if (!mptcp_timer_pending(sk))
> mptcp_reset_timer(sk);
>
> --
> 2.35.3
>
>
>
--
Mat Martineau
Intel
Hi Geliang,
Thank you for your modifications, that's great!
Our CI did some validations and here is its report:
- KVM Validation: normal:
- Unstable: 1 failed test(s): packetdrill_add_addr 🔴:
- Task: https://cirrus-ci.com/task/4741266072666112
- Summary: https://api.cirrus-ci.com/v1/artifact/task/4741266072666112/summary/summary.txt
- {"code":404,"message":
- "Can't find artifacts containing file conclusion.txt"}:
- Task: https://cirrus-ci.com/task/5867165979508736
- Summary: https://api.cirrus-ci.com/v1/artifact/task/5867165979508736/summary/summary.txt
Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/12a4c489939c
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)
Hi Geliang,
Thank you for your modifications, that's great!
Our CI did some validations and here is its report:
- KVM Validation: normal:
- Unstable: 1 failed test(s): selftest_simult_flows 🔴:
- Task: https://cirrus-ci.com/task/5202885733515264
- Summary: https://api.cirrus-ci.com/v1/artifact/task/5202885733515264/summary/summary.txt
- {"code":404,"message":
- "Can't find artifacts containing file conclusion.txt"}:
- Task: https://cirrus-ci.com/task/6328785640357888
- Summary: https://api.cirrus-ci.com/v1/artifact/task/6328785640357888/summary/summary.txt
Initiator: Patchew Applier
Commits: https://github.com/multipath-tcp/mptcp_net-next/commits/ddd3c597286e
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)
© 2016 - 2026 Red Hat, Inc.