[NET]: Size listen hash tables using backlog hint
We currently allocate a fixed size (TCP_SYNQ_HSIZE=512) slots hash table for
each LISTEN socket, regardless of various parameters (listen backlog for
example)
On x86_64, this means order-1 allocations (might fail), even for 'small'
sockets, expecting few connections. On the contrary, a huge server wanting a
backlog of 50000 is slowed down a bit because of this fixed limit.
This patch makes the sizing of listen hash table a dynamic parameter,
depending of :
- net.core.somaxconn tunable (default is 128)
- net.ipv4.tcp_max_syn_backlog tunable (default : 256, 1024 or 128)
- backlog value given by user application (2nd parameter of listen())
For large allocations (bigger than PAGE_SIZE), we use vmalloc() instead of
kmalloc().
We still limit memory allocation with the two existing tunables (somaxconn &
tcp_max_syn_backlog). So for standard setups, this patch actually reduce RAM
usage.
Signed-off-by: Eric Dumazet <dada1@cosmosbay.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/core/request_sock.c b/net/core/request_sock.c
index 79ebd75..5f0818d 100644
--- a/net/core/request_sock.c
+++ b/net/core/request_sock.c
@@ -15,6 +15,7 @@
#include <linux/random.h>
#include <linux/slab.h>
#include <linux/string.h>
+#include <linux/vmalloc.h>
#include <net/request_sock.h>
@@ -29,22 +30,31 @@
* it is absolutely not enough even at 100conn/sec. 256 cures most
* of problems. This value is adjusted to 128 for very small machines
* (<=32Mb of memory) and to 1024 on normal or better ones (>=256Mb).
- * Further increasing requires to change hash table size.
+ * Note : Dont forget somaxconn that may limit backlog too.
*/
int sysctl_max_syn_backlog = 256;
int reqsk_queue_alloc(struct request_sock_queue *queue,
- const int nr_table_entries)
+ unsigned int nr_table_entries)
{
- const int lopt_size = sizeof(struct listen_sock) +
- nr_table_entries * sizeof(struct request_sock *);
- struct listen_sock *lopt = kzalloc(lopt_size, GFP_KERNEL);
+ size_t lopt_size = sizeof(struct listen_sock);
+ struct listen_sock *lopt;
+ nr_table_entries = min_t(u32, nr_table_entries, sysctl_max_syn_backlog);
+ nr_table_entries = max_t(u32, nr_table_entries, 8);
+ nr_table_entries = roundup_pow_of_two(nr_table_entries + 1);
+ lopt_size += nr_table_entries * sizeof(struct request_sock *);
+ if (lopt_size > PAGE_SIZE)
+ lopt = __vmalloc(lopt_size,
+ GFP_KERNEL | __GFP_HIGHMEM | __GFP_ZERO,
+ PAGE_KERNEL);
+ else
+ lopt = kzalloc(lopt_size, GFP_KERNEL);
if (lopt == NULL)
return -ENOMEM;
- for (lopt->max_qlen_log = 6;
- (1 << lopt->max_qlen_log) < sysctl_max_syn_backlog;
+ for (lopt->max_qlen_log = 3;
+ (1 << lopt->max_qlen_log) < nr_table_entries;
lopt->max_qlen_log++);
get_random_bytes(&lopt->hash_rnd, sizeof(lopt->hash_rnd));
@@ -65,9 +75,11 @@
{
/* make all the listen_opt local to us */
struct listen_sock *lopt = reqsk_queue_yank_listen_sk(queue);
+ size_t lopt_size = sizeof(struct listen_sock) +
+ lopt->nr_table_entries * sizeof(struct request_sock *);
if (lopt->qlen != 0) {
- int i;
+ unsigned int i;
for (i = 0; i < lopt->nr_table_entries; i++) {
struct request_sock *req;
@@ -81,7 +93,10 @@
}
BUG_TRAP(lopt->qlen == 0);
- kfree(lopt);
+ if (lopt_size > PAGE_SIZE)
+ vfree(lopt);
+ else
+ kfree(lopt);
}
EXPORT_SYMBOL(reqsk_queue_destroy);