[ovs-discuss] A way to measure time packet/flow takes in EMC and dpcls cache

William Tu u9012063 at gmail.com
Thu Feb 22 15:58:46 UTC 2018


On Thu, Feb 22, 2018 at 6:43 AM, Att Att <attkillrocks at gmail.com> wrote:
> Hi guys
>
> I am looking for a way to measure latency of a packet when it goes through
> EMC and dpcls?I also want to test the time it spends in EMC and in dpcls
> tables. Please suggest me a way to do that.
>
> Thank you
>
Try ovs-appctl dpif-netdev/pmd-stats-show

# man ovs-vswitchd
 dpif-netdev/pmd-stats-show [dp]
              Shows performance statistics for each pmd thread of the
datapath dp.  The special thread ``main''
              sums up the statistics of every non pmd thread.  The sum
of ``emc  hits'',  ``masked  hits''  and
              ``miss''  is the number of packets received by the
datapath.  Cycles are counted using the TSC or
              similar facilities (when available on the platform).
To  reset  these  counters  use  dpif-net‐
              dev/pmd-stats-clear.  The  duration  of one cycle
depends on the measuring infrastructure. ``idle
              cycles'' refers to cycles spent polling devices  but
not  receiving  any  packets.  ``processing
              cycles''  refers  to  cycles  spent  polling devices and
successfully receiving packets, plus the
              cycles spent processing said packets.

William


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