From: Stephen Hemminger <stephen@networkplumber.org>
To: Ed Czeck <ed.czeck@atomicrules.com>
Cc: dev@dpdk.org
Subject: Re: [dpdk-dev] [PATCH v3 2/7] net/ark: HW API part 1 of 3
Date: Tue, 21 Mar 2017 15:15:52 -0700 [thread overview]
Message-ID: <20170321151552.2d172477@xeon-e3> (raw)
In-Reply-To: <1490132621-7851-2-git-send-email-ed.czeck@atomicrules.com>
On Tue, 21 Mar 2017 17:43:36 -0400
Ed Czeck <ed.czeck@atomicrules.com> wrote:
> + volatile uint32_t ctrl;
> + volatile uint32_t stats_clear;
> + volatile uint32_t cplh_max;
You are using a lot of 'volatile' in this driver.
In general volatile should be reserved for known software shared data structures
rather than every device register and statistics. I.e volatile is an inefficient
replacement for proper use of barriers. The DPDK is not as stringent as Linux
kernel (the kernel community considers almost all use of volatile a bug).
See kernel document. process/volatile-considered-harmful.rst
Do you understand that volatile requires compiler to generate the most paranoid code possible.
Basically every reference turns into a barrier.
next prev parent reply other threads:[~2017-03-21 22:15 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-21 21:43 [dpdk-dev] [PATCH v3 1/7] net/ark: PMD for Atomic Rules Arkville driver stub Ed Czeck
2017-03-21 21:43 ` [dpdk-dev] [PATCH v3 2/7] net/ark: HW API part 1 of 3 Ed Czeck
2017-03-21 22:15 ` Stephen Hemminger [this message]
2017-03-22 0:13 ` Ed Czeck
2017-03-22 0:30 ` Stephen Hemminger
2017-03-22 14:36 ` Ed Czeck
2017-03-21 21:43 ` [dpdk-dev] [PATCH v3 3/7] net/ark: HW API part 2 " Ed Czeck
2017-03-21 21:43 ` [dpdk-dev] [PATCH v3 4/7] net/ark: HW API part 3 " Ed Czeck
2017-03-21 21:43 ` [dpdk-dev] [PATCH v3 5/7] net/ark: Packet TX support initial version Ed Czeck
2017-03-21 21:43 ` [dpdk-dev] [PATCH v3 6/7] net/ark: Packet RX " Ed Czeck
2017-03-21 21:43 ` [dpdk-dev] [PATCH v3 7/7] net/ark: Arkville PMD component integration Ed Czeck
2017-03-22 18:16 ` [dpdk-dev] [PATCH v3 1/7] net/ark: PMD for Atomic Rules Arkville driver stub Ferruh Yigit
2017-03-23 1:09 ` Ed Czeck
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