netdev - Re: net: unix: Align send data_len up to PAGE

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Message-ID: <1400164076.3782.32.camel@tkhai>
Date:	Thu, 15 May 2014 18:27:56 +0400
From:	Kirill Tkhai <ktkhai@...allels.com>
To:	Eric Dumazet <eric.dumazet@...il.com>
CC:	David Miller <davem@...emloft.net>, <netdev@...r.kernel.org>,
	<edumazet@...gle.com>
Subject: Re: net: unix: Align send data_len up to PAGE_SIZE

В Чт, 15/05/2014 в 06:27 -0700, Eric Dumazet пишет:
> On Thu, 2014-05-15 at 12:54 +0400, Kirill Tkhai wrote:
> 
> > 
> > And I assumed it's OK to allocate skbs with zero header size like this:
> > 
> > sock_alloc_send_pskb(sk, 0, data_len)
> > 
> > Please say, if it's wrong.
> > 
> 
> Its OK
> 

Thanks for the reply. So, new version is below.

[PATCH]net: unix: Align send data_len up to PAGE_SIZE
    
Using whole of allocated pages reduces requested skb->data size.
This is just a little more thriftily allocation.
    
netperf does not show difference with the current performance.
    
Signed-off-by: Kirill Tkhai <ktkhai@...allels.com>
---
 net/unix/af_unix.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)

diff --git a/net/unix/af_unix.c b/net/unix/af_unix.c
index 749f80c..65d67c2 100644
--- a/net/unix/af_unix.c
+++ b/net/unix/af_unix.c
@@ -1492,10 +1492,12 @@ static int unix_dgram_sendmsg(struct kiocb *kiocb, struct socket *sock,
 	if (len > sk->sk_sndbuf - 32)
 		goto out;
 
-	if (len > SKB_MAX_ALLOC)
+	if (len > SKB_MAX_ALLOC) {
 		data_len = min_t(size_t,
 				 len - SKB_MAX_ALLOC,
 				 MAX_SKB_FRAGS * PAGE_SIZE);
+		data_len = PAGE_ALIGN(data_len);
+	}
 
 	skb = sock_alloc_send_pskb(sk, len - data_len, data_len,
 				   msg->msg_flags & MSG_DONTWAIT, &err,
@@ -1670,6 +1672,8 @@ static int unix_stream_sendmsg(struct kiocb *kiocb, struct socket *sock,
 
 		data_len = max_t(int, 0, size - SKB_MAX_HEAD(0));
 
+		data_len = min_t(size_t, size, PAGE_ALIGN(data_len));
+
 		skb = sock_alloc_send_pskb(sk, size - data_len, data_len,
 					   msg->msg_flags & MSG_DONTWAIT, &err,
 					   get_order(UNIX_SKB_FRAGS_SZ));


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