From: Stephen Hemminger <stephen@networkplumber.org>
To: "Dorsett, Michal" <Michal.Dorsett@verint.com>
Cc: "users@dpdk.org" <users@dpdk.org>
Subject: Re: [dpdk-users] movzbl in rte_eth_rx_burst
Date: Sun, 20 Aug 2017 10:56:38 -0700 [thread overview]
Message-ID: <20170820105638.4d216f50@xeon-e3> (raw)
In-Reply-To: <DAC43FCF19B05149A1D1F5E9005F94F801358EEF89@TLVMBX1.verint.corp.verintsystems.com>
On Sat, 19 Aug 2017 08:45:15 +0000
"Dorsett, Michal" <Michal.Dorsett@verint.com> wrote:
> Hi,
>
> We are running dpdk 16.07. Below is a snippet from a perf annotate report of a CPU running a thread that constantly reads packets.
> As you can see, the hottest instructruction is
>
> movzbl 0x10(%rcx),%r15d
>
> which, I believe, is referring to
>
> struct rte_eth_dev *dev = &rte_eth_devices[port_id];
>
>
> Can someone explain why this instruction is so costly, and how I can remedy this?
Perf is not accurate on exact instruction.
Your problem is that reading TSC causes a full pipeline stall on most x86 processors.
https://archive.fosdem.org/2015/schedule/event/dpdk_performance/
prev parent reply other threads:[~2017-08-20 17:56 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-08-19 8:45 Dorsett, Michal
2017-08-20 17:56 ` Stephen Hemminger [this message]
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