linux-kernel - [v3.3-rc2+ PATCH] tcp: properly initialize tcp memory limits

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Date:	Thu, 02 Feb 2012 18:07:00 +0800
From:	Jason Wang <jasowang@...hat.com>
To:	netdev@...r.kernel.org, jasowang@...hat.com, davem@...emloft.net,
	linux-kernel@...r.kernel.org, glommer@...allels.com
Cc:	mst@...hat.com
Subject: [v3.3-rc2+ PATCH] tcp: properly initialize tcp memory limits

Commit 4acb4190 tries to fix the using uninitialized value
introduced by commit 3dc43e3,  but it would make the
per-socket memory limits too small.

This patch fixes this and also remove the redundant codes
introduced in 4acb4190.

Signed-off-by: Jason Wang <jasowang@...hat.com>
---
 net/ipv4/sysctl_net_ipv4.c |    5 -----
 net/ipv4/tcp.c             |    4 ++--
 2 files changed, 2 insertions(+), 7 deletions(-)

diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
index 4cb9cd2..1eb8caa 100644
--- a/net/ipv4/sysctl_net_ipv4.c
+++ b/net/ipv4/sysctl_net_ipv4.c
@@ -815,11 +815,6 @@ static __net_init int ipv4_sysctl_init_net(struct net *net)
 	net->ipv4.sysctl_rt_cache_rebuild_count = 4;
 
 	tcp_init_mem(net);
-	limit = nr_free_buffer_pages() / 8;
-	limit = max(limit, 128UL);
-	net->ipv4.sysctl_tcp_mem[0] = limit / 4 * 3;
-	net->ipv4.sysctl_tcp_mem[1] = limit;
-	net->ipv4.sysctl_tcp_mem[2] = net->ipv4.sysctl_tcp_mem[0] * 2;
 
 	net->ipv4.ipv4_hdr = register_net_sysctl_table(net,
 			net_ipv4_ctl_path, table);
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 06373b4..3a7514b 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3218,7 +3218,6 @@ __setup("thash_entries=", set_thash_entries);
 
 void tcp_init_mem(struct net *net)
 {
-	/* Set per-socket limits to no more than 1/128 the pressure threshold */
 	unsigned long limit = nr_free_buffer_pages() / 8;
 	limit = max(limit, 128UL);
 	net->ipv4.sysctl_tcp_mem[0] = limit / 4 * 3;
@@ -3287,7 +3286,8 @@ void __init tcp_init(void)
 	sysctl_max_syn_backlog = max(128, cnt / 256);
 
 	tcp_init_mem(&init_net);
-	limit = nr_free_buffer_pages() / 8;
+	/* Set per-socket limits to no more than 1/128 the pressure threshold */
+	limit = nr_free_buffer_pages() << (PAGE_SHIFT - 10);
 	limit = max(limit, 128UL);
 	max_share = min(4UL*1024*1024, limit);
 

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