三层交换机之Flex Counter

一般情况下，BCM命令show counter <pbmp>命令可以查看各端口的包统计，但是，有时候，我们需要查看MMU入队列、出队列以及队列丢包统计。此时，就需要用到Flexible Counter Pool了。

XGS系列交换芯片有12个Flexible Counter表（Pool），每张表1024个表项，被MMU用来记录enqueue和dequeue的报文个数。

以BCM56440为例，在Ingress方向支持16K Flexible Counters(8 Pools * 2K counters)，在Egress方向支持8K Flexible Counters(8 Pools * 1K counters)。Flex Counters被划分为Interface Tables和Service Tables两个Table Groups。Flexible Counters独立于ICAP counters。

soc/common/counter.c:141: * CTR_FLEX_COUNT_0/1/2/3 = Total ENQ discarded 
soc/common/counter.c:142: * CTR_FLEX_COUNT_4/5/6/7  = Red packet ENQ discarded 
soc/common/counter.c:143: * CTR_FLEX_COUNT_8/9/10/11  = Total DEQ

soc/common/counter.c:162: * CTR_FLEX_COUNT_0 = Total ENQ discarded 
soc/common/counter.c:163: * CTR_FLEX_COUNT_1 = Total ENQ Accepted 
soc/common/counter.c:164: * CTR_FLEX_COUNT_2 = Green ENQ discarded 
soc/common/counter.c:165: * CTR_FLEX_COUNT_3 = Yellow ENQ discarded
soc/common/counter.c:166: * CTR_FLEX_COUNT_4 = Red packet ENQ discarded 
soc/common/counter.c:167: * CTR_FLEX_COUNT_5 = Green ENQ Accepted
soc/common/counter.c:168: * CTR_FLEX_COUNT_6 = Yellow ENQ Accepted
soc/common/counter.c:169: * CTR_FLEX_COUNT_7 = Red ENQ Accepted
soc/common/counter.c:170: * CTR_FLEX_COUNT_8 = Total DEQ

每个Flexible Counter Pool可以映射为某一种类型的包统计，如ENQ(enqueue)、DEQ(dequeue)等，具体配置由BCM SDK实现，以后再补充说明。

使用之前，首先需要停止counter任务的运行（设置interval为0，恢复运行时设置采集时间间隔即可），因为存在冲突。

BCM.0> counter
Current settings:
        Interval=1000000
        PortBitMap=0x00000000000000001fffffff, cpu,ge,xe
        DMA=True

BCM.0> counter interval=0

接下来，读取flex counter计数。其中，CTR_FLEX_COUNT_0表示Total ENQ Discard，即入队列丢包；CTR_FLEX_COUNT_8表示Total DEQ，即出队列包统计。

队列映射的规则为，CPU端口0~47共48个队列，物理端口每个端口8个cos队列，其他为指定入队列。

BCM.0> d chg CTR_FLEX_COUNT_0 56 8
CTR_FLEX_COUNT_0.mmu0[56]: <ECCP=0x16,ECC=0x16,DATA=0x2bda00000b,COUNT=0xb,BYTE_COUNT=0x15ed>
CTR_FLEX_COUNT_0.mmu0[57]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_0.mmu0[58]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_0.mmu0[59]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_0.mmu0[60]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_0.mmu0[61]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_0.mmu0[62]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_0.mmu0[63]: <DATA=1,COUNT=1>

BCM.0> d chg CTR_FLEX_COUNT_8 56 8
CTR_FLEX_COUNT_8.mmu0[56]: <PARITY=1,ECCP=0x59,ECC=0x19,DATA=0x310d1fa006a41,COUNT=0x6a41,BYTE_COUNT=0x18868fd>
CTR_FLEX_COUNT_8.mmu0[57]: <PARITY=1,ECCP=0x71,ECC=0x31,DATA=0x10112000147,COUNT=0x147,BYTE_COUNT=0x8089>
CTR_FLEX_COUNT_8.mmu0[58]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_8.mmu0[59]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_8.mmu0[60]: <DATA=1,COUNT=1>
CTR_FLEX_COUNT_8.mmu0[61]: <PARITY=1,ECCP=0x7c,ECC=0x3c,DATA=0x61ec29e0091a7,COUNT=0x91a7,BYTE_COUNT=0x30f614f>
CTR_FLEX_COUNT_8.mmu0[62]: <PARITY=1,ECCP=0x52,ECC=0x12,DATA=0xfe5d00003ed,COUNT=0x3ed,BYTE_COUNT=0x7f2e8>
CTR_FLEX_COUNT_8.mmu0[63]: <PARITY=1,ECCP=0x4f,ECC=0xf,DATA=0x2ad0000052,COUNT=0x52,BYTE_COUNT=0x1568>