Re: [PATCH] tcp: Add memory pressure flag to sockstat

Jay Vosburgh
2023-07-14T22:45:17Z

Jamie Bainbridge <jamie.bainbridge@gmail.com> wrote:

>When tuning a system it can be helpful to know whether the protocol is
>in memory pressure state or not. This can be determined by corresponding
>the number of pages in "net.ipv4.tcp_mem" with the current allocation,
>but a global variable already tracks this as the source of truth.
>
>Expose that variable in sockstat where other protocol memory usage is
>already reported.
>
>Add "pressure" which is 0 in normal state and 1 under pressure:
>
> # grep TCP /proc/net/sockstat
> TCP: inuse 5 orphan 0 tw 0 alloc 7 mem 1 pressure 0
>
> # grep TCP /proc/net/sockstat
> TCP: inuse 5 orphan 0 tw 0 alloc 7 mem 1 pressure 1

Isn't this already available in /proc/net/protocols?

protocol size sockets memory press maxhdr slab module cl co di ac io in de sh ss gs se re sp bi br ha uh gp em
[...]
UDP 1472 7 6 NI 0 yes kernel y y y n y y y n y y y y y n n y y y n
TCP 2512 5 1 no 320 yes kernel y y y y y y y y y y y y y n y y y y y

-J

>Tested by writing a large value to global variable tcp_memory_pressure
>(it usually stores jiffies when memory pressure was entered) and not
>just by code review or editing example output.
>
>Signed-off-by: Jamie Bainbridge <jamie.bainbridge@gmail.com>
>---
> net/ipv4/proc.c | 7 ++++---
> 1 file changed, 4 insertions(+), 3 deletions(-)
>
>diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
>index eaf1d3113b62f7dc93fdc7b7c4041140ac63bf69..f4c5ced2de49d5c6d7f5d7ccdaa76c89dcf8c932 100644
>--- a/net/ipv4/proc.c
>+++ b/net/ipv4/proc.c
>@@ -51,16 +51,17 @@
> static int sockstat_seq_show(struct seq_file *seq, void *v)
> {
> struct net *net = seq->private;
>- int orphans, sockets;
>+ int orphans, sockets, tcp_pressure;
>
> orphans = tcp_orphan_count_sum();
> sockets = proto_sockets_allocated_sum_positive(&tcp_prot);
>+ tcp_pressure = READ_ONCE(tcp_memory_pressure) ? 1 : 0;
>
> socket_seq_show(seq);
>- seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %ld\n",
>+ seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %ld pressure %d\n",
> sock_prot_inuse_get(net, &tcp_prot), orphans,
> refcount_read(&net->ipv4.tcp_death_row.tw_refcount) - 1,
>- sockets, proto_memory_allocated(&tcp_prot));
>+ sockets, proto_memory_allocated(&tcp_prot), tcp_pressure);
> seq_printf(seq, "UDP: inuse %d mem %ld\n",
> sock_prot_inuse_get(net, &udp_prot),
> proto_memory_allocated(&udp_prot));
>--
>2.41.0
>
>

---
-Jay Vosburgh, jay.vosburgh@canonical.com