Re: [RFC PATCH v3 2/7] proc: Reduce cache miss in {snmp,netstat}_seq_show

[Marcelo <marcelo.leitner@gmail.com>]

On Fri, Sep 09, 2016 at 02:33:57PM +0800, Jia He wrote:
> This is to use the generic interface snmp_get_cpu_field{,64}_batch to 
> aggregate the data by going through all the items of each cpu sequentially.
> Then snmp_seq_show and netstat_seq_show are split into 2 parts to avoid build
> warning "the frame size" larger than 1024 on s390.

Yeah about that, did you test it with stack overflow detection?
These arrays can be quite large.

One more below..

> 
> Signed-off-by: Jia He <hejianet@gmail.com>
> ---
>  net/ipv4/proc.c | 106 +++++++++++++++++++++++++++++++++++++++-----------------
>  1 file changed, 74 insertions(+), 32 deletions(-)
> 
> diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
> index 9f665b6..c6fc80e 100644
> --- a/net/ipv4/proc.c
> +++ b/net/ipv4/proc.c
> @@ -46,6 +46,8 @@
>  #include <net/sock.h>
>  #include <net/raw.h>
>  
> +#define TCPUDP_MIB_MAX max_t(u32, UDP_MIB_MAX, TCP_MIB_MAX)
> +
>  /*
>   *	Report socket allocation statistics [mea@utu.fi]
>   */
> @@ -378,13 +380,15 @@ static void icmp_put(struct seq_file *seq)
>  /*
>   *	Called from the PROCfs module. This outputs /proc/net/snmp.
>   */
> -static int snmp_seq_show(struct seq_file *seq, void *v)
> +static int snmp_seq_show_ipstats(struct seq_file *seq, void *v)
>  {
>  	int i;
> +	u64 buff64[IPSTATS_MIB_MAX];
>  	struct net *net = seq->private;
>  
> -	seq_puts(seq, "Ip: Forwarding DefaultTTL");
> +	memset(buff64, 0, IPSTATS_MIB_MAX * sizeof(u64));
>  
> +	seq_puts(seq, "Ip: Forwarding DefaultTTL");
>  	for (i = 0; snmp4_ipstats_list[i].name != NULL; i++)
>  		seq_printf(seq, " %s", snmp4_ipstats_list[i].name);
>  
> @@ -393,57 +397,77 @@ static int snmp_seq_show(struct seq_file *seq, void *v)
>  		   net->ipv4.sysctl_ip_default_ttl);
>  
>  	BUILD_BUG_ON(offsetof(struct ipstats_mib, mibs) != 0);
> +	snmp_get_cpu_field64_batch(buff64, snmp4_ipstats_list,
> +				   net->mib.ip_statistics,
> +				   offsetof(struct ipstats_mib, syncp));
>  	for (i = 0; snmp4_ipstats_list[i].name != NULL; i++)
> -		seq_printf(seq, " %llu",
> -			   snmp_fold_field64(net->mib.ip_statistics,
> -					     snmp4_ipstats_list[i].entry,
> -					     offsetof(struct ipstats_mib, syncp)));
> +		seq_printf(seq, " %llu", buff64[i]);
>  
> -	icmp_put(seq);	/* RFC 2011 compatibility */
> -	icmpmsg_put(seq);
> +	return 0;
> +}
> +
> +static int snmp_seq_show_tcp_udp(struct seq_file *seq, void *v)
> +{
> +	int i;
> +	unsigned long buff[TCPUDP_MIB_MAX];
> +	struct net *net = seq->private;
> +
> +	memset(buff, 0, TCPUDP_MIB_MAX * sizeof(unsigned long));
>  
>  	seq_puts(seq, "\nTcp:");
>  	for (i = 0; snmp4_tcp_list[i].name != NULL; i++)
>  		seq_printf(seq, " %s", snmp4_tcp_list[i].name);
>  
>  	seq_puts(seq, "\nTcp:");
> +	snmp_get_cpu_field_batch(buff, snmp4_tcp_list,
> +				 net->mib.tcp_statistics);
>  	for (i = 0; snmp4_tcp_list[i].name != NULL; i++) {
>  		/* MaxConn field is signed, RFC 2012 */
>  		if (snmp4_tcp_list[i].entry = TCP_MIB_MAXCONN)
> -			seq_printf(seq, " %ld",
> -				   snmp_fold_field(net->mib.tcp_statistics,
> -						   snmp4_tcp_list[i].entry));
> +			seq_printf(seq, " %ld", buff[i]);
>  		else
> -			seq_printf(seq, " %lu",
> -				   snmp_fold_field(net->mib.tcp_statistics,
> -						   snmp4_tcp_list[i].entry));
> +			seq_printf(seq, " %lu", buff[i]);
>  	}
>  
> +	memset(buff, 0, TCPUDP_MIB_MAX * sizeof(unsigned long));
> +
> +	snmp_get_cpu_field_batch(buff, snmp4_udp_list,
> +				 net->mib.udp_statistics);
>  	seq_puts(seq, "\nUdp:");
>  	for (i = 0; snmp4_udp_list[i].name != NULL; i++)
>  		seq_printf(seq, " %s", snmp4_udp_list[i].name);
> -
>  	seq_puts(seq, "\nUdp:");
>  	for (i = 0; snmp4_udp_list[i].name != NULL; i++)
> -		seq_printf(seq, " %lu",
> -			   snmp_fold_field(net->mib.udp_statistics,
> -					   snmp4_udp_list[i].entry));
> +		seq_printf(seq, " %lu", buff[i]);
> +
> +	memset(buff, 0, TCPUDP_MIB_MAX * sizeof(unsigned long));
>  
>  	/* the UDP and UDP-Lite MIBs are the same */
>  	seq_puts(seq, "\nUdpLite:");
> +	snmp_get_cpu_field_batch(buff, snmp4_udp_list,
> +				 net->mib.udplite_statistics);
>  	for (i = 0; snmp4_udp_list[i].name != NULL; i++)
>  		seq_printf(seq, " %s", snmp4_udp_list[i].name);
> -
>  	seq_puts(seq, "\nUdpLite:");
>  	for (i = 0; snmp4_udp_list[i].name != NULL; i++)
> -		seq_printf(seq, " %lu",
> -			   snmp_fold_field(net->mib.udplite_statistics,
> -					   snmp4_udp_list[i].entry));
> +		seq_printf(seq, " %lu", buff[i]);
>  
>  	seq_putc(seq, '\n');
>  	return 0;
>  }
>  
> +static int snmp_seq_show(struct seq_file *seq, void *v)
> +{
> +	snmp_seq_show_ipstats(seq, v);
> +
> +	icmp_put(seq);	/* RFC 2011 compatibility */
> +	icmpmsg_put(seq);
> +
> +	snmp_seq_show_tcp_udp(seq, v);
> +
> +	return 0;
> +}
> +
>  static int snmp_seq_open(struct inode *inode, struct file *file)
>  {
>  	return single_open_net(inode, file, snmp_seq_show);
> @@ -457,41 +481,59 @@ static const struct file_operations snmp_seq_fops = {
>  	.release = single_release_net,
>  };
>  
> -
> -
>  /*
>   *	Output /proc/net/netstat
>   */
> -static int netstat_seq_show(struct seq_file *seq, void *v)
> +static int netstat_seq_show_tcpext(struct seq_file *seq, void *v)
>  {
>  	int i;
> +	unsigned long buff[LINUX_MIB_MAX];
>  	struct net *net = seq->private;
>  
> +	memset(buff, 0, sizeof(unsigned long) * LINUX_MIB_MAX);
> +
>  	seq_puts(seq, "TcpExt:");
>  	for (i = 0; snmp4_net_list[i].name != NULL; i++)
>  		seq_printf(seq, " %s", snmp4_net_list[i].name);
>  
>  	seq_puts(seq, "\nTcpExt:");
> +	snmp_get_cpu_field_batch(buff, snmp4_net_list,
> +				 net->mib.net_statistics);
>  	for (i = 0; snmp4_net_list[i].name != NULL; i++)
> -		seq_printf(seq, " %lu",
> -			   snmp_fold_field(net->mib.net_statistics,
> -					   snmp4_net_list[i].entry));
> +		seq_printf(seq, " %lu", buff[i]);
> +
> +	return 0;
> +}
> +
> +static int netstat_seq_show_ipext(struct seq_file *seq, void *v)
> +{
> +	int i;
> +	u64 buff64[IPSTATS_MIB_MAX];
> +	struct net *net = seq->private;
>  
>  	seq_puts(seq, "\nIpExt:");
>  	for (i = 0; snmp4_ipextstats_list[i].name != NULL; i++)
>  		seq_printf(seq, " %s", snmp4_ipextstats_list[i].name);
>  
>  	seq_puts(seq, "\nIpExt:");

You're missing a memset() call here.

> +	snmp_get_cpu_field64_batch(buff64, snmp4_ipextstats_list,
> +				   net->mib.ip_statistics,
> +				   offsetof(struct ipstats_mib, syncp));
>  	for (i = 0; snmp4_ipextstats_list[i].name != NULL; i++)
> -		seq_printf(seq, " %llu",
> -			   snmp_fold_field64(net->mib.ip_statistics,
> -					     snmp4_ipextstats_list[i].entry,
> -					     offsetof(struct ipstats_mib, syncp)));
> +		seq_printf(seq, " %llu", buff64[i]);
>  
>  	seq_putc(seq, '\n');
>  	return 0;
>  }
>  
> +static int netstat_seq_show(struct seq_file *seq, void *v)
> +{
> +	netstat_seq_show_tcpext(seq, v);
> +	netstat_seq_show_ipext(seq, v);
> +
> +	return 0;
> +}
> +
>  static int netstat_seq_open(struct inode *inode, struct file *file)
>  {
>  	return single_open_net(inode, file, netstat_seq_show);
> -- 
> 1.8.3.1
> 
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