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From: "Xie, Huawei" <huawei.xie@intel.com>
To: Stephen Hemminger <stephen@networkplumber.org>
Cc: "dev@dpdk.org" <dev@dpdk.org>
Subject: Re: [dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers
Date: Tue, 27 Jan 2015 16:16:10 +0000	[thread overview]
Message-ID: <C37D651A908B024F974696C65296B57B0F362A77@SHSMSX101.ccr.corp.intel.com> (raw)
In-Reply-To: <20150127095831.1572b67a@uryu.home.lan>



> -----Original Message-----
> From: Stephen Hemminger [mailto:stephen@networkplumber.org]
> Sent: Tuesday, January 27, 2015 5:59 PM
> To: Xie, Huawei
> Cc: Ouyang, Changchun; dev@dpdk.org
> Subject: Re: [dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers
> 
> 
> > I recall our original code is virtio_wmb().
> > Use store fence to ensure all updates to entries before updating the index.
> > Why do we need virtio_rmb() here and add virtio_wmb after
> vq_update_avail_idx()?
> 
> Store fence is unnecessary, Intel CPU's are cache coherent, please read
> the virtio Linux ring header file for explanation. A full fence WMB
> is more expensive and causes CPU stall
> 


I mean virtio_wmb rather than virtio_rmb should be used here, 
and both of them are defined as compiler barrier.

The following code is linux virtio driver for adding buffer to vring.
/* Put entry in available array (but don't update avail->idx until they
	 * do sync). */
	avail = (vq->vring.avail->idx & (vq->vring.num-1));
	vq->vring.avail->ring[avail] = head;

	/* Descriptors and available array need to be set before we expose the
	 * new available array entries. */
	virtio_wmb(vq->weak_barriers);
	vq->vring.avail->idx++;

> > >  	vq->vq_ring.avail->idx = vq->vq_avail_idx;
> > >  }
> > >
> > > @@ -255,7 +264,7 @@ static inline void
> > >  virtqueue_notify(struct virtqueue *vq)
> > >  {
> > >  	/*
> > > -	 * Ensure updated avail->idx is visible to host. mb() necessary?
> > > +	 * Ensure updated avail->idx is visible to host.
> > >  	 * For virtio on IA, the notificaiton is through io port operation
> > >  	 * which is a serialization instruction itself.
> > >  	 */
> > > --
> > > 1.8.4.2
> >

  reply	other threads:[~2015-01-27 16:16 UTC|newest]

Thread overview: 132+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-01-15  5:15 [dpdk-dev] [PATCH 00/22] Single virtio implementation Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 01/22] virtio: Rearrange resource initialization Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 02/22] virtio: Use weaker barriers Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 03/22] virtio: Allow starting with link down Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 04/22] virtio: Add support for Link State interrupt Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 05/22] ether: Add soft vlan encap/decap functions Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 06/22] virtio: Use software vlan stripping Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 07/22] virtio: Remove unnecessary adapter structure Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 08/22] virtio: Remove redundant vq_alignment Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 09/22] virtio: Fix how states are handled during initialization Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 10/22] virtio: Make vtpci_get_status local Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 11/22] virtio: Check for packet headroom at compile time Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 12/22] virtio: Move allocation before initialization Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 13/22] virtio: Add support for vlan filtering Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 14/22] virtio: Add suport for multiple mac addresses Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 15/22] virtio: Add ability to set MAC address Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 16/22] virtio: Free mbuf's with threshold Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 17/22] virtio: Use port IO to get PCI resource Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 18/22] virtio: Fix descriptor index issue Ouyang Changchun
2015-01-15 16:54   ` Stephen Hemminger
2015-01-16  0:55     ` Ouyang, Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 19/22] ether: Fix vlan strip/insert issue Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 20/22] example/vhost: Avoid inserting vlan twice Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 21/22] example/vhost: Add vlan-strip cmd line option Ouyang Changchun
2015-01-15  5:15 ` [dpdk-dev] [PATCH 22/22] virtio: Use soft vlan strip in mergeable Rx path Ouyang Changchun
2015-01-15 16:55   ` Stephen Hemminger
2015-01-16  0:56     ` Ouyang, Changchun
2015-01-27  2:35 ` [dpdk-dev] [PATCH v2 00/24] Single virtio implementation Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 01/24] virtio: Rearrange resource initialization Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 02/24] virtio: Use weaker barriers Ouyang Changchun
2015-01-27  7:03     ` Xie, Huawei
2015-01-27  9:58       ` Stephen Hemminger
2015-01-27 16:16         ` Xie, Huawei [this message]
2015-01-28  6:12           ` Ouyang, Changchun
2015-01-27  7:56     ` Xie, Huawei
2015-01-27  8:04       ` Ouyang, Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 03/24] virtio: Allow starting with link down Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 04/24] virtio: Add support for Link State interrupt Ouyang Changchun
2015-01-27  9:04     ` Xie, Huawei
2015-01-27 10:00       ` Stephen Hemminger
2015-01-28  3:03         ` Ouyang, Changchun
2015-01-28 15:11           ` Stephen Hemminger
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 05/24] ether: Add soft vlan encap/decap functions Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 06/24] virtio: Use software vlan stripping Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 07/24] virtio: Remove unnecessary adapter structure Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 08/24] virtio: Remove redundant vq_alignment Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 09/24] virtio: Fix how states are handled during initialization Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 10/24] virtio: Make vtpci_get_status local Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 11/24] virtio: Check for packet headroom at compile time Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 12/24] virtio: Move allocation before initialization Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 13/24] virtio: Add support for vlan filtering Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 14/24] virtio: Add suport for multiple mac addresses Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 15/24] virtio: Add ability to set MAC address Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 16/24] virtio: Free mbuf's with threshold Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 17/24] virtio: Use port IO to get PCI resource Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 18/24] virtio: Fix descriptor index issue Ouyang Changchun
2015-01-27  2:35   ` [dpdk-dev] [PATCH v2 19/24] ether: Fix vlan strip/insert issue Ouyang Changchun
2015-01-27  2:36   ` [dpdk-dev] [PATCH v2 20/24] example/vhost: Avoid inserting vlan twice Ouyang Changchun
2015-01-27  2:36   ` [dpdk-dev] [PATCH v2 21/24] example/vhost: Add vlan-strip cmd line option Ouyang Changchun
2015-01-27  2:36   ` [dpdk-dev] [PATCH v2 22/24] virtio: Use soft vlan strip in mergeable Rx path Ouyang Changchun
2015-01-27  2:36   ` [dpdk-dev] [PATCH v2 23/24] virtio: Fix zero copy break issue Ouyang Changchun
2015-01-27  2:36   ` [dpdk-dev] [PATCH v2 24/24] virtio: Remove hotspots Ouyang Changchun
2015-01-27  3:06   ` [dpdk-dev] [PATCH v2 00/24] Single virtio implementation Matthew Hall
2015-01-27  3:42     ` Wiles, Keith
2015-01-27  9:41       ` Matthew Hall
2015-01-27 10:02     ` Stephen Hemminger
2015-01-27 18:59       ` Matthew Hall
2015-01-29  7:23   ` [dpdk-dev] [PATCH v3 00/25] " Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 01/25] virtio: Rearrange resource initialization Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 02/25] virtio: Use weaker barriers Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 03/25] virtio: Allow starting with link down Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 04/25] virtio: Add support for Link State interrupt Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 05/25] ether: Add soft vlan encap/decap functions Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 06/25] virtio: Use software vlan stripping Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 07/25] virtio: Remove unnecessary adapter structure Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 08/25] virtio: Remove redundant vq_alignment Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 09/25] virtio: Fix how states are handled during initialization Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 10/25] virtio: Make vtpci_get_status local Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 11/25] virtio: Check for packet headroom at compile time Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 12/25] virtio: Move allocation before initialization Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 13/25] virtio: Add support for vlan filtering Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 14/25] virtio: Add suport for multiple mac addresses Ouyang Changchun
2015-01-29  7:23     ` [dpdk-dev] [PATCH v3 15/25] virtio: Add ability to set MAC address Ouyang Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 16/25] virtio: Free mbuf's with threshold Ouyang Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 17/25] virtio: Use port IO to get PCI resource Ouyang Changchun
2015-01-29 23:14       ` Thomas Monjalon
2015-02-04  1:31         ` Ouyang, Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 18/25] virtio: Fix descriptor index issue Ouyang Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 19/25] ether: Fix vlan strip/insert issue Ouyang Changchun
2015-02-04 10:54       ` Xie, Huawei
2015-02-05  0:54         ` Ouyang, Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 20/25] example/vhost: Avoid inserting vlan twice Ouyang Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 21/25] example/vhost: Add vlan-strip cmd line option Ouyang Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 22/25] virtio: Use soft vlan strip in mergeable Rx path Ouyang Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 23/25] virtio: Fix zero copy break issue Ouyang Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 24/25] virtio: Remove hotspots Ouyang Changchun
2015-01-29  7:24     ` [dpdk-dev] [PATCH v3 25/25] virtio: Fix wmb issue Ouyang Changchun
2015-02-09  1:13     ` [dpdk-dev] [PATCH v4 00/26] Single virtio implementation Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 01/26] virtio: Rearrange resource initialization Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 02/26] virtio: Use weaker barriers Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 03/26] virtio: Allow starting with link down Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 04/26] virtio: Add support for Link State interrupt Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 05/26] ether: Add soft vlan encap/decap functions Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 06/26] virtio: Use software vlan stripping Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 07/26] virtio: Remove unnecessary adapter structure Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 08/26] virtio: Remove redundant vq_alignment Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 09/26] virtio: Fix how states are handled during initialization Ouyang Changchun
2015-02-09  1:13       ` [dpdk-dev] [PATCH v4 10/26] virtio: Make vtpci_get_status local Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 11/26] virtio: Check for packet headroom at compile time Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 12/26] virtio: Move allocation before initialization Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 13/26] virtio: Add support for vlan filtering Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 14/26] virtio: Add suport for multiple mac addresses Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 15/26] virtio: Add ability to set MAC address Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 16/26] virtio: Free mbuf's with threshold Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 17/26] virtio: Use port IO to get PCI resource Ouyang Changchun
2015-02-11  4:32         ` Stephen Hemminger
2015-02-11  4:50           ` Ouyang, Changchun
2015-02-11  7:29             ` Vincent JARDIN
2015-02-11 13:50               ` Stephen Hemminger
2015-02-11 14:16                 ` Thomas Monjalon
2015-02-12  0:52                   ` Ouyang, Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 18/26] virtio: Fix descriptor index issue Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 19/26] ether: Fix vlan strip/insert issue Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 20/26] example/vhost: Avoid inserting vlan twice Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 21/26] example/vhost: Add vlan-strip cmd line option Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 22/26] virtio: Use soft vlan strip in mergeable Rx path Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 23/26] virtio: Fix zero copy break issue Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 24/26] virtio: Remove hotspots Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 25/26] virtio: Fix wmb issue Ouyang Changchun
2015-02-09  1:14       ` [dpdk-dev] [PATCH v4 26/26] virtio: Fix updating vring descriptor index issue Ouyang Changchun
2015-02-17  6:04       ` [dpdk-dev] [PATCH v4 00/26] Single virtio implementation Xie, Huawei
2015-02-20 18:06         ` Thomas Monjalon

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