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Merge branch 'tcp-mem-pressure-fixes'

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Eric Dumazet says:

====================
tcp: final (?) round of mem pressure fixes

While working on prior patch series (e10b02ee5b "Merge branch
'net-reduce-tcp_memory_allocated-inflation'"), I found that we
could still have frozen TCP flows under memory pressure.

I thought we had solved this in 2015, but the fix was not complete.

v2: deal with zerocopy tx paths.
====================

Signed-off-by: David S. Miller <davem@davemloft.net>
This commit is contained in:
David S. Miller 2022-06-17 10:11:04 +01:00
commit e42134b57e
2 changed files with 50 additions and 7 deletions
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50
net/ipv4/tcp.c
View File

@ -951,6 +951,40 @@ static int tcp_downgrade_zcopy_pure(struct sock *sk, struct sk_buff *skb)
return 0;
}
static int tcp_wmem_schedule(struct sock *sk, int copy)
{
int left;
if (likely(sk_wmem_schedule(sk, copy)))
return copy;
/* We could be in trouble if we have nothing queued.
* Use whatever is left in sk->sk_forward_alloc and tcp_wmem[0]
* to guarantee some progress.
*/
left = sock_net(sk)->ipv4.sysctl_tcp_wmem[0] - sk->sk_wmem_queued;
if (left > 0)
sk_forced_mem_schedule(sk, min(left, copy));
return min(copy, sk->sk_forward_alloc);
}
static int tcp_wmem_schedule(struct sock *sk, int copy)
{
int left;
if (likely(sk_wmem_schedule(sk, copy)))
return copy;
/* We could be in trouble if we have nothing queued.
* Use whatever is left in sk->sk_forward_alloc and tcp_wmem[0]
* to guarantee some progress.
*/
left = sock_net(sk)->ipv4.sysctl_tcp_wmem[0] - sk->sk_wmem_queued;
if (left > 0)
sk_forced_mem_schedule(sk, min(left, copy));
return min(copy, sk->sk_forward_alloc);
}
static struct sk_buff *tcp_build_frag(struct sock *sk, int size_goal, int flags,
struct page *page, int offset, size_t *size)
{
@ -986,7 +1020,11 @@ new_segment:
tcp_mark_push(tp, skb);
goto new_segment;
}
if (tcp_downgrade_zcopy_pure(sk, skb) || !sk_wmem_schedule(sk, copy))
if (tcp_downgrade_zcopy_pure(sk, skb))
return NULL;
copy = tcp_wmem_schedule(sk, copy);
if (!copy)
return NULL;
if (can_coalesce) {
@ -1334,8 +1372,11 @@ new_segment:
copy = min_t(int, copy, pfrag->size - pfrag->offset);
if (tcp_downgrade_zcopy_pure(sk, skb) ||
!sk_wmem_schedule(sk, copy))
if (tcp_downgrade_zcopy_pure(sk, skb))
goto wait_for_space;
copy = tcp_wmem_schedule(sk, copy);
if (!copy)
goto wait_for_space;
err = skb_copy_to_page_nocache(sk, &msg->msg_iter, skb,
@ -1362,7 +1403,8 @@ new_segment:
skb_shinfo(skb)->flags |= SKBFL_PURE_ZEROCOPY;
if (!skb_zcopy_pure(skb)) {
if (!sk_wmem_schedule(sk, copy))
copy = tcp_wmem_schedule(sk, copy);
if (!copy)
goto wait_for_space;
}

7
net/ipv4/tcp_output.c
View File

@ -3362,11 +3362,12 @@ void tcp_xmit_retransmit_queue(struct sock *sk)
*/
void sk_forced_mem_schedule(struct sock *sk, int size)
{
int amt;
int delta, amt;
if (size <= sk->sk_forward_alloc)
delta = size - sk->sk_forward_alloc;
if (delta <= 0)
return;
amt = sk_mem_pages(size);
amt = sk_mem_pages(delta);
sk->sk_forward_alloc += amt << PAGE_SHIFT;
sk_memory_allocated_add(sk, amt);