net: refine {udp|tcp|sctp}_mem limits

Current tcp/udp/sctp global memory limits are not taking into account
hugepages allocations, and allow 50% of ram to be used by buffers of a
single protocol [ not counting space used by sockets / inodes ...]

Lets use nr_free_buffer_pages() and allow a default of 1/8 of kernel ram
per protocol, and a minimum of 128 pages.
Heavy duty machines sysadmins probably need to tweak limits anyway.


References: https://bugzilla.stlinux.com/show_bug.cgi?id=38032
Reported-by: starlight <starlight@binnacle.cx>
Suggested-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

2 files changed, 4 insertions, 16 deletions

diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 054a59d21eb0..46febcacb729 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -3220,7 +3220,7 @@ __setup("thash_entries=", set_thash_entries);
 void __init tcp_init(void)
 {
         struct sk_buff *skb = NULL;
-        unsigned long nr_pages, limit;
+        unsigned long limit;
         int i, max_share, cnt;
         unsigned long jiffy = jiffies;
 
@@ -3277,13 +3277,7 @@ void __init tcp_init(void)
         sysctl_tcp_max_orphans = cnt / 2;
         sysctl_max_syn_backlog = max(128, cnt / 256);
 
-        /* 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.
-         */
-        nr_pages = totalram_pages - totalhigh_pages;
-        limit = min(nr_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
-        limit = (limit * (nr_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
+        limit = nr_free_buffer_pages() / 8;
         limit = max(limit, 128UL);
         sysctl_tcp_mem[0] = limit / 4 * 3;
         sysctl_tcp_mem[1] = limit;
diff --git a/net/ipv4/udp.c b/net/ipv4/udp.c
index 48cd88e62553..198f75b7bdd3 100644
--- a/net/ipv4/udp.c
+++ b/net/ipv4/udp.c
@@ -2209,16 +2209,10 @@ void __init udp_table_init(struct udp_table *table, const char *name)
 
 void __init udp_init(void)
 {
-        unsigned long nr_pages, limit;
+        unsigned long limit;
 
         udp_table_init(&udp_table, "UDP");
-        /* Set the pressure threshold up by the same strategy of TCP. It is 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.
-         */
-        nr_pages = totalram_pages - totalhigh_pages;
-        limit = min(nr_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
-        limit = (limit * (nr_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
+        limit = nr_free_buffer_pages() / 8;
         limit = max(limit, 128UL);
         sysctl_udp_mem[0] = limit / 4 * 3;
         sysctl_udp_mem[1] = limit;