From: "Gaëtan Rivet" <gaetan.rivet@6wind.com>
To: Yuliang Li <yuliang.li@yale.edu>
Cc: users@dpdk.org
Subject: Re: [dpdk-users] occasionally ~300us delay
Date: Wed, 28 Feb 2018 10:27:28 +0100 [thread overview]
Message-ID: <20180228092728.ezf2zic2vjfpzalq@bidouze.vm.6wind.com> (raw)
In-Reply-To: <CAECc8jpQGD3tXNED8vkbaP1K2u68Oz3qwKVv32RMGZA=3PD28w@mail.gmail.com>
Hi,
On Wed, Feb 28, 2018 at 12:03:30AM -0500, Yuliang Li wrote:
> Also, such pause happens regularly--every 0.5s.
>
> On Wed, Feb 28, 2018 at 12:01 AM, Yuliang Li <yuliang.li@yale.edu> wrote:
>
> > Hi all,
> >
> > I am using dpdk to generate packets. Specifically, I have a list of
> > <packet Pi, time Ti>, meaning I want to send Pi at Ti. I wait for Ti by while
> > (rte_get_tsc_cycles()<Ti). However, sometimes I see a delay of around
> > 300us of sending packets, i.e., the sending time of some Pi is around
> > Ti+300us. It looks like the program just pauses by 300us, and then resumes.
> > Does anyone know why?
> >
> > Thanks,
>
I would reduce entropy and gather more data.
You can isolate your process (i.e. numactl), if possible not on core 0, disable
hyper-threading, disable CPU frequency scaling.
Then, running your app:
# grep ctxt_sw /proc/$(pidof your-dpdk-app)/status
If you have context switches, then you have other tasks throwing off your measures.
The rte-intr-thread is notorious for having bad affinities and triggering context
switches, and can be used for alarms (thus, possible regular occurence).
Regards,
--
Gaëtan Rivet
6WIND
next prev parent reply other threads:[~2018-02-28 9:27 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-28 5:01 Yuliang Li
2018-02-28 5:03 ` Yuliang Li
2018-02-28 9:27 ` Gaëtan Rivet [this message]
2018-02-28 15:15 ` Stephen Hemminger
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