[TCP]: Fix tcp_mem[] initialization.

Change tcp_mem initialization function.  The fraction of total memory
is now a continuous function of memory size, and independent of page
size.

Signed-off-by: John Heffner <jheffner@psc.edu>
Signed-off-by: David S. Miller <davem@davemloft.net>

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 74c4d10..3834b10 100644 (file)
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2458,11 +2458,18 @@ void __init tcp_init(void)
                sysctl_max_syn_backlog = 128;
        }
 
-       /* Allow no more than 3/4 kernel memory (usually less) allocated to TCP */
-       sysctl_tcp_mem[0] = (1536 / sizeof (struct inet_bind_hashbucket)) << order;
-       sysctl_tcp_mem[1] = sysctl_tcp_mem[0] * 4 / 3;
+       /* Set the pressure threshold to be a fraction of global memory that
+        * is up to 1/2 at 256 MB, decreasing toward zero with the amount of
+        * memory, with a floor of 128 pages.
+        */
+       limit = min(nr_all_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
+       limit = (limit * (nr_all_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
+       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;
 
+       /* Set per-socket limits to no more than 1/128 the pressure threshold */
        limit = ((unsigned long)sysctl_tcp_mem[1]) << (PAGE_SHIFT - 7);
        max_share = min(4UL*1024*1024, limit);