[PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow

MPTCP Linux Development
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* [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow
@ 2022-06-20 16:19 Paolo Abeni
  2022-06-20 16:19 ` [PATCH net-next v3 2/3] mptcp: drop SK_RECLAIM_* macros Paolo Abeni
                   ` (2 more replies)
  0 siblings, 3 replies; 6+ messages in thread
From: Paolo Abeni @ 2022-06-20 16:19 UTC (permalink / raw)
  To: mptcp

The memory accounting is broken in such exceptional code
path, and after commit 4890b686f408 ("net: keep sk->sk_forward_alloc
as small as possible") we can't find much help there.

Drop the broken code.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
This is possibly for net, but makes sense only on top of recent
net-next patches, so whatever ;)
---
 net/mptcp/protocol.c | 11 +++--------
 1 file changed, 3 insertions(+), 8 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 6d2aa41390e7..0d4b2c010da0 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -328,15 +328,10 @@ static bool mptcp_rmem_schedule(struct sock *sk, struct sock *ssk, int size)
 
 	amt = sk_mem_pages(size);
 	amount = amt << PAGE_SHIFT;
-	msk->rmem_fwd_alloc += amount;
-	if (!__sk_mem_raise_allocated(sk, size, amt, SK_MEM_RECV)) {
-		if (ssk->sk_forward_alloc < amount) {
-			msk->rmem_fwd_alloc -= amount;
-			return false;
-		}
+	if (!__sk_mem_raise_allocated(sk, size, amt, SK_MEM_RECV))
+		return false;
 
-		ssk->sk_forward_alloc -= amount;
-	}
+	msk->rmem_fwd_alloc += amount;
 	return true;
 }
 
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* [PATCH net-next v3 2/3] mptcp: drop SK_RECLAIM_* macros
  2022-06-20 16:19 [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow Paolo Abeni
@ 2022-06-20 16:19 ` Paolo Abeni
  2022-06-20 20:38   ` Mat Martineau
  2022-06-20 16:19 ` [PATCH net-next v3 3/3] mptcp: refine memory scheduling Paolo Abeni
  2022-06-20 16:46 ` [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow Paolo Abeni
  2 siblings, 1 reply; 6+ messages in thread
From: Paolo Abeni @ 2022-06-20 16:19 UTC (permalink / raw)
  To: mptcp

After commit 4890b686f408 ("net: keep sk->sk_forward_alloc as small as
possible"), the MPTCP protocol is the last SK_RECLAIM_CHUNK and
SK_RECLAIM_THRESHOLD users.

Update the MPTCP reclaim schema to match the core/TCP one and drop the
mentioned macros. This additionally clean the MPTCP code a bit.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/protocol.c | 35 ++---------------------------------
 1 file changed, 2 insertions(+), 33 deletions(-)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index 0d4b2c010da0..b31bac33f87a 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -181,8 +181,8 @@ static void mptcp_rmem_uncharge(struct sock *sk, int size)
 	reclaimable = msk->rmem_fwd_alloc - sk_unused_reserved_mem(sk);
 
 	/* see sk_mem_uncharge() for the rationale behind the following schema */
-	if (unlikely(reclaimable >= SK_RECLAIM_THRESHOLD))
-		__mptcp_rmem_reclaim(sk, SK_RECLAIM_CHUNK);
+	if (unlikely(reclaimable >= PAGE_SIZE))
+		__mptcp_rmem_reclaim(sk, reclaimable);
 }
 
 static void mptcp_rfree(struct sk_buff *skb)
@@ -961,25 +961,6 @@ static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
 		df->data_seq + df->data_len == msk->write_seq;
 }
 
-static void __mptcp_mem_reclaim_partial(struct sock *sk)
-{
-	int reclaimable = mptcp_sk(sk)->rmem_fwd_alloc - sk_unused_reserved_mem(sk);
-
-	lockdep_assert_held_once(&sk->sk_lock.slock);
-
-	if (reclaimable > (int)PAGE_SIZE)
-		__mptcp_rmem_reclaim(sk, reclaimable - 1);
-
-	sk_mem_reclaim(sk);
-}
-
-static void mptcp_mem_reclaim_partial(struct sock *sk)
-{
-	mptcp_data_lock(sk);
-	__mptcp_mem_reclaim_partial(sk);
-	mptcp_data_unlock(sk);
-}
-
 static void dfrag_uncharge(struct sock *sk, int len)
 {
 	sk_mem_uncharge(sk, len);
@@ -999,7 +980,6 @@ static void __mptcp_clean_una(struct sock *sk)
 {
 	struct mptcp_sock *msk = mptcp_sk(sk);
 	struct mptcp_data_frag *dtmp, *dfrag;
-	bool cleaned = false;
 	u64 snd_una;
 
 	/* on fallback we just need to ignore snd_una, as this is really
@@ -1022,7 +1002,6 @@ static void __mptcp_clean_una(struct sock *sk)
 		}
 
 		dfrag_clear(sk, dfrag);
-		cleaned = true;
 	}
 
 	dfrag = mptcp_rtx_head(sk);
@@ -1044,7 +1023,6 @@ static void __mptcp_clean_una(struct sock *sk)
 		dfrag->already_sent -= delta;
 
 		dfrag_uncharge(sk, delta);
-		cleaned = true;
 	}
 
 	/* all retransmitted data acked, recovery completed */
@@ -1052,9 +1030,6 @@ static void __mptcp_clean_una(struct sock *sk)
 		msk->recovery = false;
 
 out:
-	if (cleaned && tcp_under_memory_pressure(sk))
-		__mptcp_mem_reclaim_partial(sk);
-
 	if (snd_una == READ_ONCE(msk->snd_nxt) &&
 	    snd_una == READ_ONCE(msk->write_seq)) {
 		if (mptcp_timer_pending(sk) && !mptcp_data_fin_enabled(msk))
@@ -1206,12 +1181,6 @@ static struct sk_buff *mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk, boo
 {
 	gfp_t gfp = data_lock_held ? GFP_ATOMIC : sk->sk_allocation;
 
-	if (unlikely(tcp_under_memory_pressure(sk))) {
-		if (data_lock_held)
-			__mptcp_mem_reclaim_partial(sk);
-		else
-			mptcp_mem_reclaim_partial(sk);
-	}
 	return __mptcp_alloc_tx_skb(sk, ssk, gfp);
 }
 
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* Re: [PATCH net-next v3 2/3] mptcp: drop SK_RECLAIM_* macros
  2022-06-20 16:19 ` [PATCH net-next v3 2/3] mptcp: drop SK_RECLAIM_* macros Paolo Abeni
@ 2022-06-20 20:38   ` Mat Martineau
  0 siblings, 0 replies; 6+ messages in thread
From: Mat Martineau @ 2022-06-20 20:38 UTC (permalink / raw)
  To: Paolo Abeni; +Cc: mptcp

On Mon, 20 Jun 2022, Paolo Abeni wrote:

> After commit 4890b686f408 ("net: keep sk->sk_forward_alloc as small as
> possible"), the MPTCP protocol is the last SK_RECLAIM_CHUNK and
> SK_RECLAIM_THRESHOLD users.
>
> Update the MPTCP reclaim schema to match the core/TCP one and drop the
> mentioned macros. This additionally clean the MPTCP code a bit.
>

Please also add one more patch to the series that deletes SK_RECLAIM_* 
from include/net/sock.h

- Mat

> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/mptcp/protocol.c | 35 ++---------------------------------
> 1 file changed, 2 insertions(+), 33 deletions(-)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index 0d4b2c010da0..b31bac33f87a 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -181,8 +181,8 @@ static void mptcp_rmem_uncharge(struct sock *sk, int size)
> 	reclaimable = msk->rmem_fwd_alloc - sk_unused_reserved_mem(sk);
>
> 	/* see sk_mem_uncharge() for the rationale behind the following schema */
> -	if (unlikely(reclaimable >= SK_RECLAIM_THRESHOLD))
> -		__mptcp_rmem_reclaim(sk, SK_RECLAIM_CHUNK);
> +	if (unlikely(reclaimable >= PAGE_SIZE))
> +		__mptcp_rmem_reclaim(sk, reclaimable);
> }
>
> static void mptcp_rfree(struct sk_buff *skb)
> @@ -961,25 +961,6 @@ static bool mptcp_frag_can_collapse_to(const struct mptcp_sock *msk,
> 		df->data_seq + df->data_len == msk->write_seq;
> }
>
> -static void __mptcp_mem_reclaim_partial(struct sock *sk)
> -{
> -	int reclaimable = mptcp_sk(sk)->rmem_fwd_alloc - sk_unused_reserved_mem(sk);
> -
> -	lockdep_assert_held_once(&sk->sk_lock.slock);
> -
> -	if (reclaimable > (int)PAGE_SIZE)
> -		__mptcp_rmem_reclaim(sk, reclaimable - 1);
> -
> -	sk_mem_reclaim(sk);
> -}
> -
> -static void mptcp_mem_reclaim_partial(struct sock *sk)
> -{
> -	mptcp_data_lock(sk);
> -	__mptcp_mem_reclaim_partial(sk);
> -	mptcp_data_unlock(sk);
> -}
> -
> static void dfrag_uncharge(struct sock *sk, int len)
> {
> 	sk_mem_uncharge(sk, len);
> @@ -999,7 +980,6 @@ static void __mptcp_clean_una(struct sock *sk)
> {
> 	struct mptcp_sock *msk = mptcp_sk(sk);
> 	struct mptcp_data_frag *dtmp, *dfrag;
> -	bool cleaned = false;
> 	u64 snd_una;
>
> 	/* on fallback we just need to ignore snd_una, as this is really
> @@ -1022,7 +1002,6 @@ static void __mptcp_clean_una(struct sock *sk)
> 		}
>
> 		dfrag_clear(sk, dfrag);
> -		cleaned = true;
> 	}
>
> 	dfrag = mptcp_rtx_head(sk);
> @@ -1044,7 +1023,6 @@ static void __mptcp_clean_una(struct sock *sk)
> 		dfrag->already_sent -= delta;
>
> 		dfrag_uncharge(sk, delta);
> -		cleaned = true;
> 	}
>
> 	/* all retransmitted data acked, recovery completed */
> @@ -1052,9 +1030,6 @@ static void __mptcp_clean_una(struct sock *sk)
> 		msk->recovery = false;
>
> out:
> -	if (cleaned && tcp_under_memory_pressure(sk))
> -		__mptcp_mem_reclaim_partial(sk);
> -
> 	if (snd_una == READ_ONCE(msk->snd_nxt) &&
> 	    snd_una == READ_ONCE(msk->write_seq)) {
> 		if (mptcp_timer_pending(sk) && !mptcp_data_fin_enabled(msk))
> @@ -1206,12 +1181,6 @@ static struct sk_buff *mptcp_alloc_tx_skb(struct sock *sk, struct sock *ssk, boo
> {
> 	gfp_t gfp = data_lock_held ? GFP_ATOMIC : sk->sk_allocation;
>
> -	if (unlikely(tcp_under_memory_pressure(sk))) {
> -		if (data_lock_held)
> -			__mptcp_mem_reclaim_partial(sk);
> -		else
> -			mptcp_mem_reclaim_partial(sk);
> -	}
> 	return __mptcp_alloc_tx_skb(sk, ssk, gfp);
> }
>
> -- 
> 2.35.3
>
>
>

--
Mat Martineau
Intel

^ permalink raw reply	[flat|nested] 6+ messages in thread

* [PATCH net-next v3 3/3] mptcp: refine memory scheduling
  2022-06-20 16:19 [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow Paolo Abeni
  2022-06-20 16:19 ` [PATCH net-next v3 2/3] mptcp: drop SK_RECLAIM_* macros Paolo Abeni
@ 2022-06-20 16:19 ` Paolo Abeni
  2022-06-20 20:32   ` Mat Martineau
  2022-06-20 16:46 ` [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow Paolo Abeni
  2 siblings, 1 reply; 6+ messages in thread
From: Paolo Abeni @ 2022-06-20 16:19 UTC (permalink / raw)
  To: mptcp

Similar to commit 7c80b038d23e ("net: fix sk_wmem_schedule() and
sk_rmem_schedule() errors"), let the MPTCP receive path schedule
exactly the required amount of memory.

Signed-off-by: Paolo Abeni <pabeni@redhat.com>
---
 net/mptcp/protocol.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
index b31bac33f87a..0e295b3bce54 100644
--- a/net/mptcp/protocol.c
+++ b/net/mptcp/protocol.c
@@ -326,6 +326,7 @@ static bool mptcp_rmem_schedule(struct sock *sk, struct sock *ssk, int size)
 	if (size < msk->rmem_fwd_alloc)
 		return true;
 
+	size -= msk->rmem_fwd_alloc;
 	amt = sk_mem_pages(size);
 	amount = amt << PAGE_SHIFT;
 	if (!__sk_mem_raise_allocated(sk, size, amt, SK_MEM_RECV))
-- 
2.35.3


^ permalink raw reply related	[flat|nested] 6+ messages in thread

* Re: [PATCH net-next v3 3/3] mptcp: refine memory scheduling
  2022-06-20 16:19 ` [PATCH net-next v3 3/3] mptcp: refine memory scheduling Paolo Abeni
@ 2022-06-20 20:32   ` Mat Martineau
  0 siblings, 0 replies; 6+ messages in thread
From: Mat Martineau @ 2022-06-20 20:32 UTC (permalink / raw)
  To: Paolo Abeni; +Cc: mptcp

On Mon, 20 Jun 2022, Paolo Abeni wrote:

> Similar to commit 7c80b038d23e ("net: fix sk_wmem_schedule() and
> sk_rmem_schedule() errors"), let the MPTCP receive path schedule
> exactly the required amount of memory.
>
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>
> ---
> net/mptcp/protocol.c | 1 +
> 1 file changed, 1 insertion(+)
>
> diff --git a/net/mptcp/protocol.c b/net/mptcp/protocol.c
> index b31bac33f87a..0e295b3bce54 100644
> --- a/net/mptcp/protocol.c
> +++ b/net/mptcp/protocol.c
> @@ -326,6 +326,7 @@ static bool mptcp_rmem_schedule(struct sock *sk, struct sock *ssk, int size)
> 	if (size < msk->rmem_fwd_alloc)

With the change below, also would be good to change the above line to:

 	if (size <= msk->rmem_fwd_alloc)

so there's no attempt to allocate 0 new pages.

> 		return true;
>
> +	size -= msk->rmem_fwd_alloc;
> 	amt = sk_mem_pages(size);
> 	amount = amt << PAGE_SHIFT;
> 	if (!__sk_mem_raise_allocated(sk, size, amt, SK_MEM_RECV))
> -- 
> 2.35.3
>
>
>

--
Mat Martineau
Intel

^ permalink raw reply	[flat|nested] 6+ messages in thread

* Re: [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow
  2022-06-20 16:19 [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow Paolo Abeni
  2022-06-20 16:19 ` [PATCH net-next v3 2/3] mptcp: drop SK_RECLAIM_* macros Paolo Abeni
  2022-06-20 16:19 ` [PATCH net-next v3 3/3] mptcp: refine memory scheduling Paolo Abeni
@ 2022-06-20 16:46 ` Paolo Abeni
  2 siblings, 0 replies; 6+ messages in thread
From: Paolo Abeni @ 2022-06-20 16:46 UTC (permalink / raw)
  To: mptcp

On Mon, 2022-06-20 at 18:19 +0200, Paolo Abeni wrote:
> The memory accounting is broken in such exceptional code
> path, and after commit 4890b686f408 ("net: keep sk->sk_forward_alloc
> as small as possible") we can't find much help there.
> 
> Drop the broken code.
> 
> Signed-off-by: Paolo Abeni <pabeni@redhat.com>

This is actually a "v2" ;)

The only change is the new patch 3/3 - I even kept the obsolete comment
after the commit message in patch 1/3 :)

/P


^ permalink raw reply	[flat|nested] 6+ messages in thread

end of thread, other threads:[~2022-06-20 20:38 UTC | newest]

Thread overview: 6+ messages (download: mbox.gz follow: Atom feed
-- links below jump to the message on this page --
2022-06-20 16:19 [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow Paolo Abeni
2022-06-20 16:19 ` [PATCH net-next v3 2/3] mptcp: drop SK_RECLAIM_* macros Paolo Abeni
2022-06-20 20:38   ` Mat Martineau
2022-06-20 16:19 ` [PATCH net-next v3 3/3] mptcp: refine memory scheduling Paolo Abeni
2022-06-20 20:32   ` Mat Martineau
2022-06-20 16:46 ` [PATCH net-next v3 1/3] mptcp: never fetch fwd memory from the subflow Paolo Abeni

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