diff mbox

[net-next] net: rps: don't skip offline cpus when set rps_cpus

Message ID 20170515125552.2971-1-zlpnobody@163.com
State Changes Requested, archived
Delegated to: David Miller
Headers show

Commit Message

Liping Zhang May 15, 2017, 12:55 p.m. UTC 
From: Liping Zhang <zlpnobody@gmail.com>

On our 4-core system, sometimes I can enable all CPUs to process packets.
But sometimes I can't, if all the CPUs become offline except core 0, I
will get the following result, which is really annoying for my script:
 # echo f > /sys/class/net/eth0/queues/rx-0/rps_cpus
 # cat /sys/class/net/eth0/queues/rx-0/rps_cpus
 1

Since we won't steer the packets to these offline cpus, it's reasonable
to enable all configed cpus to the rps_map, even if they are offline for
the time being.

Signed-off-by: Liping Zhang <zlpnobody@gmail.com>
---
 net/core/net-sysfs.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

David Miller May 15, 2017, 2:23 p.m. UTC | #1 
From: Liping Zhang <zlpnobody@163.com>
Date: Mon, 15 May 2017 20:55:52 +0800

> From: Liping Zhang <zlpnobody@gmail.com>
> 
> On our 4-core system, sometimes I can enable all CPUs to process packets.
> But sometimes I can't, if all the CPUs become offline except core 0, I
> will get the following result, which is really annoying for my script:
>  # echo f > /sys/class/net/eth0/queues/rx-0/rps_cpus
>  # cat /sys/class/net/eth0/queues/rx-0/rps_cpus
>  1
> 
> Since we won't steer the packets to these offline cpus, it's reasonable
> to enable all configed cpus to the rps_map, even if they are offline for
> the time being.
> 
> Signed-off-by: Liping Zhang <zlpnobody@gmail.com>

But this means while those cpus are offline, get_rps_cpu() performs
very suboptimally.

In fact, if the packet hashes to one of those offline cpus, you get
no RPS at all.

So I think we really can't make this change, at least in it's current
form.
diff mbox

Patch

diff --git a/net/core/net-sysfs.c b/net/core/net-sysfs.c
index 65ea0ff..8adb36d 100644
--- a/net/core/net-sysfs.c
+++ b/net/core/net-sysfs.c
@@ -731,7 +731,7 @@  static ssize_t store_rps_map(struct netdev_rx_queue *queue,
 	}
 
 	i = 0;
-	for_each_cpu_and(cpu, mask, cpu_online_mask)
+	for_each_cpu_and(cpu, mask, cpu_possible_mask)
 		map->cpus[i++] = cpu;
 
 	if (i)