DPDK patches and discussions
 help / color / mirror / Atom feed
From: Thomas Monjalon <thomas@monjalon.net>
To: Jianbo Liu <jianbo.liu@arm.com>,
	Andrew Rybchenko <arybchenko@solarflare.com>,
	Yongseok Koh <yskoh@mellanox.com>
Cc: dev@dpdk.org, adrien.mazarguil@6wind.com,
	nelio.laranjeiro@6wind.com, jerin.jacob@caviumnetworks.com,
	konstantin.ananyev@intel.com, bruce.richardson@intel.com,
	Chao Zhu <chaozhu@linux.vnet.ibm.com>
Subject: Re: [dpdk-dev] [PATCH v2 1/8] eal: introduce DMA memory barriers
Date: Wed, 17 Jan 2018 14:46:21 +0100	[thread overview]
Message-ID: <3720864.2redlIt54T@xps> (raw)
In-Reply-To: <20180116091040.GA15629@arm.com>

16/01/2018 10:10, Jianbo Liu:
> The 01/16/2018 10:49, Andrew Rybchenko wrote:
> > On 01/16/2018 04:10 AM, Yongseok Koh wrote:
> > >This commit introduces rte_dma_wmb() and rte_dma_rmb(), in order to
> > >guarantee the ordering of coherent shared memory between the CPU and a DMA
> > >capable device.
> > >
> > >Signed-off-by: Yongseok Koh <yskoh@mellanox.com>
> > >---
> > >  lib/librte_eal/common/include/generic/rte_atomic.h | 18 ++++++++++++++++++
> > >  1 file changed, 18 insertions(+)
> > >
> > >diff --git a/lib/librte_eal/common/include/generic/rte_atomic.h b/lib/librte_eal/common/include/generic/rte_atomic.h
> > >index 16af5ca57..2e0503ce6 100644
> > >--- a/lib/librte_eal/common/include/generic/rte_atomic.h
> > >+++ b/lib/librte_eal/common/include/generic/rte_atomic.h
> > >@@ -98,6 +98,24 @@ static inline void rte_io_wmb(void);
> > >   */
> > >  static inline void rte_io_rmb(void);
> > >+/**
> > >+ * Write memory barrier for coherent memory between lcore and IO device
> > >+ *
> > >+ * Guarantees that the STORE operations on coherent memory that
> > >+ * precede the rte_dma_wmb() call are visible to I/O device before the
> > >+ * STORE operations that follow it.
> > >+ */
> > >+static inline void rte_dma_wmb(void);
> > >+
> > >+/**
> > >+ * Read memory barrier for coherent memory between lcore and IO device
> > >+ *
> > >+ * Guarantees that the LOAD operations on coherent memory updated by
> > >+ * IO device that precede the rte_dma_rmb() call are visible to CPU
> > >+ * before the LOAD operations that follow it.
> > >+ */
> > >+static inline void rte_dma_rmb(void);
> > >+
> > >  #endif /* __DOXYGEN__ */
> > >  /**
> >
> > I'm not an ARMv8 expert so, my comments could be a bit ignorant.
> > I'd like to understand the difference between io and added here dma
> > barriers.
> > The difference should be clearly explained. Otherwise we'll constantly hit
> > on incorrect choice of barrier type.
> > Also I don't understand why "dma" name is chosen taking into account
> > that definition is bound to coherent memory between lcore and IO device.
> 
> A good explanation can be found here.
> 
> https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=1077fa36f23e259858caf6f269a47393a5aff523

I agree that something more is needed to explain when to use rte_io_*.
The only difference between rte_io_* and rte_dma_* is "on coherent memory".

  reply	other threads:[~2018-01-17 13:46 UTC|newest]

Thread overview: 49+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2017-12-27  4:28 [dpdk-dev] [PATCH 1/2] eal/arm64: modify I/O device " Yongseok Koh
2017-12-27  4:28 ` [dpdk-dev] [PATCH 2/2] net/mlx5: fix synchonization on polling Rx completions Yongseok Koh
2018-01-04 12:58 ` [dpdk-dev] [PATCH 1/2] eal/arm64: modify I/O device memory barriers Jerin Jacob
2018-01-08  1:55 ` Jianbo Liu
2018-01-16  0:42   ` Yongseok Koh
2018-01-16  1:10 ` [dpdk-dev] [PATCH v2 0/8] introduce DMA " Yongseok Koh
2018-01-16  1:10   ` [dpdk-dev] [PATCH v2 1/8] eal: " Yongseok Koh
2018-01-16  2:47     ` Jianbo Liu
2018-01-16  7:49     ` Andrew Rybchenko
2018-01-16  9:10       ` Jianbo Liu
2018-01-17 13:46         ` Thomas Monjalon [this message]
2018-01-17 18:39           ` Yongseok Koh
2018-01-18 11:56             ` Andrew Rybchenko
2018-01-18 18:14               ` Yongseok Koh
2018-01-16  1:10   ` [dpdk-dev] [PATCH v2 2/8] eal/x86: define " Yongseok Koh
2018-01-16  1:10   ` [dpdk-dev] [PATCH v2 3/8] eal/ppc64: define DMA device " Yongseok Koh
2018-01-16  1:10   ` [dpdk-dev] [PATCH v2 4/8] eal/armv7: define DMA " Yongseok Koh
2018-01-16  2:48     ` Jianbo Liu
2018-01-16  1:10   ` [dpdk-dev] [PATCH v2 5/8] eal/arm64: " Yongseok Koh
2018-01-16  2:50     ` Jianbo Liu
2018-01-16  1:10   ` [dpdk-dev] [PATCH v2 6/8] net/mlx5: remove unnecessary memory barrier Yongseok Koh
2018-01-16  1:10   ` [dpdk-dev] [PATCH v2 7/8] net/mlx5: replace IO memory barrier with DMA " Yongseok Koh
2018-01-16  1:10   ` [dpdk-dev] [PATCH v2 8/8] net/mlx5: fix synchonization on polling Rx completions Yongseok Koh
2018-01-16  3:53     ` Jianbo Liu
2018-01-19  0:44   ` [dpdk-dev] [PATCH v3 0/8] introduce DMA memory barriers Yongseok Koh
2018-01-19  0:44     ` [dpdk-dev] [PATCH v3 1/8] eal: " Yongseok Koh
2018-01-19  7:16       ` Andrew Rybchenko
2018-01-22 18:29         ` Yongseok Koh
2018-01-22 20:59           ` Thomas Monjalon
2018-01-23  4:35           ` Jerin Jacob
2018-01-25 19:08             ` Yongseok Koh
2018-01-19  0:44     ` [dpdk-dev] [PATCH v3 2/8] eal/x86: define " Yongseok Koh
2018-01-19  0:44     ` [dpdk-dev] [PATCH v3 3/8] eal/ppc64: " Yongseok Koh
2018-01-19  0:44     ` [dpdk-dev] [PATCH v3 4/8] eal/armv7: " Yongseok Koh
2018-01-19  0:44     ` [dpdk-dev] [PATCH v3 5/8] eal/arm64: " Yongseok Koh
2018-01-19  0:44     ` [dpdk-dev] [PATCH v3 6/8] net/mlx5: remove unnecessary memory barrier Yongseok Koh
2018-01-19  0:44     ` [dpdk-dev] [PATCH v3 7/8] net/mlx5: replace IO memory barrier with DMA " Yongseok Koh
2018-01-19  0:44     ` [dpdk-dev] [PATCH v3 8/8] net/mlx5: fix synchonization on polling Rx completions Yongseok Koh
2018-01-25 21:02     ` [dpdk-dev] [PATCH v4 0/9] introduce coherent I/O memory barriers Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 1/9] eal: add Doxygen grouping for " Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 2/9] eal: introduce coherent I/O " Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 3/9] eal/x86: define " Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 4/9] eal/ppc64: " Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 5/9] eal/armv7: " Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 6/9] eal/arm64: " Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 7/9] net/mlx5: remove unnecessary memory barrier Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 8/9] net/mlx5: replace I/O memory barrier with coherent version Yongseok Koh
2018-01-25 21:02       ` [dpdk-dev] [PATCH v4 9/9] net/mlx5: fix synchronization on polling Rx completions Yongseok Koh
2018-01-28  7:32       ` [dpdk-dev] [PATCH v4 0/9] introduce coherent I/O memory barriers Thomas Monjalon

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=3720864.2redlIt54T@xps \
    --to=thomas@monjalon.net \
    --cc=adrien.mazarguil@6wind.com \
    --cc=arybchenko@solarflare.com \
    --cc=bruce.richardson@intel.com \
    --cc=chaozhu@linux.vnet.ibm.com \
    --cc=dev@dpdk.org \
    --cc=jerin.jacob@caviumnetworks.com \
    --cc=jianbo.liu@arm.com \
    --cc=konstantin.ananyev@intel.com \
    --cc=nelio.laranjeiro@6wind.com \
    --cc=yskoh@mellanox.com \
    /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).