inetpeer: use div64_ul() and clamp_val() calculate inet_peer_threshold

In inet_initpeers(), struct inet_peer on IA32 uses 128 bytes in nowdays.
Get rid of the cascade and use div64_ul() and clamp_val() calculate that
will not need to be adjusted in the future as suggested by Eric Dumazet.
Suggested-by: NEric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: NYejune Deng <yejune.deng@gmail.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

net/ipv4/inetpeer.c

@@ -65,7 +65,7 @@ EXPORT_SYMBOL_GPL(inet_peer_base_init);
 #define PEER_MAX_GC 32
 
 /* Exported for sysctl_net_ipv4.  */
-int inet_peer_threshold __read_mostly = 65536 + 128;	/* start to throw entries more
+int inet_peer_threshold __read_mostly;	/* start to throw entries more
 					 * aggressively at this stage */
 int inet_peer_minttl __read_mostly = 120 * HZ;	/* TTL under high load: 120 sec */
 int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;	/* usual time to live: 10 min */
@@ -73,20 +73,13 @@ int inet_peer_maxttl __read_mostly = 10 * 60 * HZ;	/* usual time to live: 10 min
 /* Called from ip_output.c:ip_init  */
 void __init inet_initpeers(void)
 {
-	struct sysinfo si;
+	u64 nr_entries;
 
-	/* Use the straight interface to information about memory. */
-	si_meminfo(&si);
-	/* The values below were suggested by Alexey Kuznetsov
-	 * <kuznet@ms2.inr.ac.ru>.  I don't have any opinion about the values
-	 * myself.  --SAW
-	 */
-	if (si.totalram <= (32768*1024)/PAGE_SIZE)
-		inet_peer_threshold >>= 1; /* max pool size about 1MB on IA32 */
-	if (si.totalram <= (16384*1024)/PAGE_SIZE)
-		inet_peer_threshold >>= 1; /* about 512KB */
-	if (si.totalram <= (8192*1024)/PAGE_SIZE)
-		inet_peer_threshold >>= 2; /* about 128KB */
+	 /* 1% of physical memory */
+	nr_entries = div64_ul((u64)totalram_pages() << PAGE_SHIFT,
+			      100 * L1_CACHE_ALIGN(sizeof(struct inet_peer)));
+
+	inet_peer_threshold = clamp_val(nr_entries, 4096, 65536 + 128);
 
 	peer_cachep = kmem_cache_create("inet_peer_cache",
 			sizeof(struct inet_peer),