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>

1 files changed, 1 insertions, 10 deletions

diff --git a/net/sctp/protocol.c b/net/sctp/protocol.c
index 67380a29e2e9..207175b2f40a 100644
--- a/net/sctp/protocol.c
+++ b/net/sctp/protocol.c
@@ -1058,7 +1058,6 @@ SCTP_STATIC __init int sctp_init(void)
         int status = -EINVAL;
         unsigned long goal;
         unsigned long limit;
-        unsigned long nr_pages;
         int max_share;
         int order;
 
@@ -1148,15 +1147,7 @@ SCTP_STATIC __init int sctp_init(void)
         /* Initialize handle used for association ids. */
         idr_init(&sctp_assocs_id);
 
-        /* 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.
-         * Note this initializes the data in sctpv6_prot too
-         * Unabashedly stolen from tcp_init
-         */
-        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_sctp_mem[0] = limit / 4 * 3;
         sysctl_sctp_mem[1] = limit;