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

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