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".
next prev parent 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
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