From: Stephen Hemminger <stephen@networkplumber.org>
To: "Gaëtan Rivet" <gaetan.rivet@6wind.com>
Cc: Yuliang Li <yuliang.li@yale.edu>, users@dpdk.org
Subject: Re: [dpdk-users] occasionally ~300us delay
Date: Wed, 28 Feb 2018 07:15:20 -0800 [thread overview]
Message-ID: <20180228071520.3e9d090f@xeon-e3> (raw)
In-Reply-To: <20180228092728.ezf2zic2vjfpzalq@bidouze.vm.6wind.com>
On Wed, 28 Feb 2018 10:27:28 +0100
Gaëtan Rivet <gaetan.rivet@6wind.com> wrote:
> 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,
Sounds like SMI
prev parent reply other threads:[~2018-02-28 15:15 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
2018-02-28 15:15 ` Stephen Hemminger [this message]
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180228071520.3e9d090f@xeon-e3 \
--to=stephen@networkplumber.org \
--cc=gaetan.rivet@6wind.com \
--cc=users@dpdk.org \
--cc=yuliang.li@yale.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).