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authorEric Dumazet <edumazet@google.com>2021-09-29 18:03:33 -0700
committerDavid S. Miller <davem@davemloft.net>2021-09-30 14:17:10 +0100
commitacbd0c8144138b6e652240bba248910d330d71bf (patch)
treec8834059bb0c4d98bf6446de0c7d2b8b59d377f6 /net/mptcp
parent59f09ae8fac4a990070fc6bdc889d0e0118664ea (diff)
downloadlinux-acbd0c8144138b6e652240bba248910d330d71bf.tar.gz
mptcp: use batch snmp operations in mptcp_seq_show()
Using snmp_get_cpu_field_batch() allows for better cpu cache
utilization, especially on hosts with large number of cpus.

Also remove special handling when mptcp mibs where not yet
allocated.

I chose to use temporary storage on the stack to keep this patch simple.
We might in the future use the storage allocated in netstat_seq_show().

Combined with prior patch (inlining snmp_get_cpu_field)
time to fetch and output mptcp counters on a 256 cpu host [1]
goes from 75 usec to 16 usec.

[1] L1 cache size is 32KB, it is not big enough to hold all dataset.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/mptcp')
-rw-r--r--net/mptcp/mib.c17
1 files changed, 7 insertions, 10 deletions
diff --git a/net/mptcp/mib.c b/net/mptcp/mib.c
index b21ff9be04c6..3240b72271a7 100644
--- a/net/mptcp/mib.c
+++ b/net/mptcp/mib.c
@@ -72,6 +72,7 @@ bool mptcp_mib_alloc(struct net *net)
 
 void mptcp_seq_show(struct seq_file *seq)
 {
+	unsigned long sum[ARRAY_SIZE(mptcp_snmp_list) - 1];
 	struct net *net = seq->private;
 	int i;
 
@@ -81,17 +82,13 @@ void mptcp_seq_show(struct seq_file *seq)
 
 	seq_puts(seq, "\nMPTcpExt:");
 
-	if (!net->mib.mptcp_statistics) {
-		for (i = 0; mptcp_snmp_list[i].name; i++)
-			seq_puts(seq, " 0");
-
-		seq_putc(seq, '\n');
-		return;
-	}
+	memset(sum, 0, sizeof(sum));
+	if (net->mib.mptcp_statistics)
+		snmp_get_cpu_field_batch(sum, mptcp_snmp_list,
+					 net->mib.mptcp_statistics);
 
 	for (i = 0; mptcp_snmp_list[i].name; i++)
-		seq_printf(seq, " %lu",
-			   snmp_fold_field(net->mib.mptcp_statistics,
-					   mptcp_snmp_list[i].entry));
+		seq_printf(seq, " %lu", sum[i]);
+
 	seq_putc(seq, '\n');
 }