tcp: halves tcp_mem[] limits

Allowing tcp to use ~19% of physical memory is way too much,
and allowed bugs to be hidden. Add to this that some drivers use a full
page per incoming frame, so real cost can be twice the advertized one.

Reduce tcp_mem by 50 % as a first step to sanity.

tcp_mem[0,1,2] defaults are now 4.68%, 6.25%, 9.37% of physical memory.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 9eabfd3e092563b2d8830b15199f180a2a2df9fb..c724195e586287760e9406c3bccde4b3d0c0c75e 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3068,11 +3068,12 @@ __setup("thash_entries=", set_thash_entries);
 
 static void __init tcp_init_mem(void)
 {
-       unsigned long limit = nr_free_buffer_pages() / 8;
+       unsigned long limit = nr_free_buffer_pages() / 16;
+
        limit = max(limit, 128UL);
-       sysctl_tcp_mem[0] = limit / 4 * 3;
-       sysctl_tcp_mem[1] = limit;
-       sysctl_tcp_mem[2] = sysctl_tcp_mem[0] * 2;
+       sysctl_tcp_mem[0] = limit / 4 * 3;              /* 4.68 % */
+       sysctl_tcp_mem[1] = limit;                      /* 6.25 % */
+       sysctl_tcp_mem[2] = sysctl_tcp_mem[0] * 2;      /* 9.37 % */
 }
 
 void __init tcp_init(void)