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[PATCH] Compact sk_stream_mem_schedule() code [message #23513] Mon, 19 November 2007 12:13 Go to previous message
Pavel Emelianov is currently offline  Pavel Emelianov
Messages: 1149
Registered: September 2006
Senior Member
This function references sk->sk_prot->xxx for many times.
It turned out, that there's so many code in it, that gcc 
cannot always optimize access to sk->sk_prot's fields.

After saving the sk->sk_prot on the stack and comparing
disassembled code, it turned out that the function became
~10 bytes shorter and made less dereferences (on i386 and 
x86_64). Stack consumption didn't grow.

Besides, this patch drives most of this function into the
80 columns limit.

Signed-off-by: Pavel Emelyanov <xemul@openvz.org>

---

diff --git a/net/core/stream.c b/net/core/stream.c
index 755bacb..b2fb846 100644
--- a/net/core/stream.c
+++ b/net/core/stream.c
@@ -210,35 +210,36 @@ EXPORT_SYMBOL(__sk_stream_mem_reclaim);
 int sk_stream_mem_schedule(struct sock *sk, int size, int kind)
 {
 	int amt = sk_stream_pages(size);
+	struct proto *prot = sk->sk_prot;
 
 	sk->sk_forward_alloc += amt * SK_STREAM_MEM_QUANTUM;
-	atomic_add(amt, sk->sk_prot->memory_allocated);
+	atomic_add(amt, prot->memory_allocated);
 
 	/* Under limit. */
-	if (atomic_read(sk->sk_prot->memory_allocated) < sk->sk_prot->sysctl_mem[0]) {
-		if (*sk->sk_prot->memory_pressure)
-			*sk->sk_prot->memory_pressure = 0;
+	if (atomic_read(prot->memory_allocated) < prot->sysctl_mem[0]) {
+		if (*prot->memory_pressure)
+			*prot->memory_pressure = 0;
 		return 1;
 	}
 
 	/* Over hard limit. */
-	if (atomic_read(sk->sk_prot->memory_allocated) > sk->sk_prot->sysctl_mem[2]) {
-		sk->sk_prot->enter_memory_pressure();
+	if (atomic_read(prot->memory_allocated) > prot->sysctl_mem[2]) {
+		prot->enter_memory_pressure();
 		goto suppress_allocation;
 	}
 
 	/* Under pressure. */
-	if (atomic_read(sk->sk_prot->memory_allocated) > sk->sk_prot->sysctl_mem[1])
-		sk->sk_prot->enter_memory_pressure();
+	if (atomic_read(prot->memory_allocated) > prot->sysctl_mem[1])
+		prot->enter_memory_pressure();
 
 	if (kind) {
-		if (atomic_read(&sk->sk_rmem_alloc) < sk->sk_prot->sysctl_rmem[0])
+		if (atomic_read(&sk->sk_rmem_alloc) < prot->sysctl_rmem[0])
 			return 1;
-	} else if (sk->sk_wmem_queued < sk->sk_prot->sysctl_wmem[0])
+	} else if (sk->sk_wmem_queued < prot->sysctl_wmem[0])
 		return 1;
 
-	if (!*sk->sk_prot->memory_pressure ||
-	    sk->sk_prot->sysctl_mem[2] > atomic_read(sk->sk_prot->sockets_allocated) *
+	if (!*prot->memory_pressure ||
+	    prot->sysctl_mem[2] > atomic_read(prot->sockets_allocated) *
 				sk_stream_pages(sk->sk_wmem_queued +
 						atomic_read(&sk->sk_rmem_alloc) +
 						sk->sk_forward_alloc))
@@ -258,7 +259,7 @@ suppress_allocation:
 
 	/* Alas. Undo changes. */
 	sk->sk_forward_alloc -= amt * SK_STREAM_MEM_QUANTUM;
-	atomic_sub(amt, sk->sk_prot->memory_allocated);
+	atomic_sub(amt, prot->memory_allocated);
 	return 0;
 }
 
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