netdev - Weird NET_RX softirq behavior

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [thread-next>] [day] [month] [year] [list]

Message-ID: <20140807171050.77819b10@xhacker>
Date:	Thu, 7 Aug 2014 17:10:50 +0800
From:	Jisheng Zhang <jszhang@...vell.com>
To:	<davem@...emloft.net>, <netdev@...r.kernel.org>,
	<linux-kernel@...r.kernel.org>
Subject: Weird NET_RX softirq behavior

Hi list,

I observed one weird NET_RX softirq behavior:


1. CONFIG_RPS=y in kernel config file.

2. only one netdev in the system: eth0. eth0 only has one interrupt which is
all handled by CPU0. eth0 doesn't support RFS_ACCEL

"cat /proc/interrupts" shows 

~ # cat /proc/interrupts 
           CPU0       CPU1       CPU2       CPU3       
...
 49:         52          0          0          0       GIC  mmc1
 52:         53          0          0          0       GIC  mmc2
 56:     430365          0          0          0       GIC  eth0
 60:         61          0          0          0       GIC  mmc0
...

3. RPS and RFS remains disabled as default.

~ # ls /sys/class/net/eth0/queues/
rx-0  rx-1  rx-2  rx-3  tx-0
~ # cat /sys/class/net/eth0/queues/rx-*/rps_cpus
0
0
0
0
~ # cat /proc/sys/net/core/rps_sock_flow_entries
0
~ # cat /sys/class/net/eth0/queues/rx-*/rps_flow_cnt
0
0
0
0

4. But NET_RX seems abnormal
~ # cat /proc/softirqs 
                    CPU0       CPU1       CPU2       CPU3       
          HI:          0          0          0          0
       TIMER:      92386        767        367        263
      NET_TX:       6338          0          0          1
      NET_RX:     445587        322        983          0
       BLOCK:          0          0          0          0
BLOCK_IOPOLL:          0          0          0          0
     TASKLET:        150          0          0          0
       SCHED:      31414        490        275        179
     HRTIMER:          1          0          0          0
         RCU:      49029        570        285        182

I'm expecting NET_RX under CPU1, 2, 3 should be zero. Any suggestions
about this abnormal behavior?

Thanks in advance,
Jisheng
--
To unsubscribe from this list: send the line "unsubscribe netdev" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html