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

Krish attkillrocks at gmail.com
Fri Feb 23 04:34:12 UTC 2018

Thanks William, but I need a timestamp when a packet enters the switch and
EMC and when it leaves.
I am thinking if I can do it by coding. Can you please refer me to a way to
accomplish this, in which file do I need to add it?

Thank You

On Thu, Feb 22, 2018 at 11:58 PM, William Tu <u9012063 at gmail.com> wrote:

> 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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