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mptcp: use batch snmp operations in mptcp_seq_show()

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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>
This commit is contained in:
Eric Dumazet 2021-09-29 18:03:33 -07:00 committed by David S. Miller
parent 59f09ae8fa
commit acbd0c8144
1 changed files with 7 additions and 10 deletions
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17
net/mptcp/mib.c
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@ -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');
}