From: Ed Czeck <ed.czeck@atomicrules.com>
To: Stephen Hemminger <stephen@networkplumber.org>
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 20:13:48 -0400 [thread overview]
Message-ID: <CALZ3GujU86qSU81Ks+-V9v6XxyKBnL7WB9ukZMZGD66JEqynvw@mail.gmail.com> (raw)
In-Reply-To: <20170321151552.2d172477@xeon-e3>
Hi Stephen,
Yes I understand the paranoid issue of volatile modifier, which is the
reason it was coded in this manner.
The struct with volatile are memory mapped IO structures. These structure
are not instantiated in memory and hence do not incur concurrent (host)
software access. The a vast majority of the fields as read-only (as viewed
by the host.) The concurrency model is that hardware is the producer, and
the host the consumer. There is no handshake other than the host must not
expect the memory location to remain constant -- that is optimization off.
As for performance, these structures are not in any critical path, so he
optimization path is correctness not performance.
Do you have a recommendation for changing this code without using the
volatile modifier? I have requirements from the hardware in the pattern of:
write a 1 to location x
read from location y until it become 0
write a 0 to location x
How can this work without a volatile modified on x and y?
Best,
Ed.
next prev parent reply other threads:[~2017-03-22 0:14 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
2017-03-22 0:13 ` Ed Czeck [this message]
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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