[PATCH linux-next] net: record times of netdev_budget exhausted

yang.yang29
2022-12-03T08:12:20Z

From: Yang Yang <yang.yang29@zte.com>

A long time ago time_squeeze was used to only record netdev_budget
exhausted[1]. Then we added netdev_budget_usecs to enable softirq
tuning[2]. And when polling elapsed netdev_budget_usecs, it's also
record by time_squeeze.
For tuning netdev_budget and netdev_budget_usecs respectively, we'd
better distinguish netdev_budget exhausted from netdev_budget_usecs
elapsed, so add a new recorder to record netdev_budget exhausted.

[1] commit 1da177e4c3f4("Linux-2.6.12-rc2")
[2] commit 7acf8a1e8a28("Replace 2 jiffies with sysctl netdev_budget_usecs to enable softirq tuning")

Signed-off-by: Yang Yang <yang.yang29@zte.com>
---
include/linux/netdevice.h | 1 +
net/core/dev.c | 11 +++++++----
net/core/net-procfs.c | 5 +++--
3 files changed, 11 insertions(+), 6 deletions(-)

diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h
index 5aa35c58c342..a77719b956a6 100644
--- a/include/linux/netdevice.h
+++ b/include/linux/netdevice.h
@@ -3135,6 +3135,7 @@ struct softnet_data {
/* stats */
unsigned int processed;
unsigned int time_squeeze;
+ unsigned int budget_exhaust;
#ifdef CONFIG_RPS
struct softnet_data *rps_ipi_list;
#endif
diff --git a/net/core/dev.c b/net/core/dev.c
index 7627c475d991..42ae2dc62661 100644
--- a/net/core/dev.c
+++ b/net/core/dev.c
@@ -6663,11 +6663,14 @@ static __latent_entropy void net_rx_action(struct softirq_action *h)
budget -= napi_poll(n, &repoll);

/* If softirq window is exhausted then punt.
- * Allow this to run for 2 jiffies since which will allow
- * an average latency of 1.5/HZ.
+ * The window is controlled by time and packet budget.
+ * See Documentation/admin-guide/sysctl/net.rst for details.
*/
- if (unlikely(budget <= 0 ||
- time_after_eq(jiffies, time_limit))) {
+ if (unlikely(budget <= 0)) {
+ sd->budget_exhaust++;
+ break;
+ }
+ if (unlikely(time_after_eq(jiffies, time_limit))) {
sd->time_squeeze++;
break;
}
diff --git a/net/core/net-procfs.c b/net/core/net-procfs.c
index 1ec23bf8b05c..e09e245125f0 100644
--- a/net/core/net-procfs.c
+++ b/net/core/net-procfs.c
@@ -169,12 +169,13 @@ static int softnet_seq_show(struct seq_file *seq, void *v)
* mapping the data a specific CPU
*/
seq_printf(seq,
- "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x\n",
+ "%08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x %08x\n",
sd->processed, sd->dropped, sd->time_squeeze, 0,
0, 0, 0, 0, /* was fastroute */
0, /* was cpu_collision */
sd->received_rps, flow_limit_count,
- softnet_backlog_len(sd), (int)seq->index);
+ softnet_backlog_len(sd), (int)seq->index
+ sd->budget_exhaust);
return 0;
}

--
2.15.2