From: Ilya Maximets <i.maximets@samsung.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: dev@dpdk.org, Huawei Xie <huawei.xie@intel.com>,
Dyasly Sergey <s.dyasly@samsung.com>
Subject: Re: [dpdk-dev] [PATCH v4] vhost: use SMP barriers instead of compiler ones.
Date: Mon, 21 Mar 2016 07:49:54 +0300 [thread overview]
Message-ID: <56EF7D72.1050108@samsung.com> (raw)
In-Reply-To: <20160318124102.GV979@yliu-dev.sh.intel.com>
On 18.03.2016 15:41, Yuanhan Liu wrote:
> On Fri, Mar 18, 2016 at 03:23:53PM +0300, Ilya Maximets wrote:
>> Since commit 4c02e453cc62 ("eal: introduce SMP memory barriers") virtio
>> uses architecture dependent SMP barriers. vHost should use them too.
>>
>> Fixes: 4c02e453cc62 ("eal: introduce SMP memory barriers")
>>
>> Signed-off-by: Ilya Maximets <i.maximets@samsung.com>
>> ---
>> lib/librte_vhost/vhost_rxtx.c | 7 ++++---
>> 1 file changed, 4 insertions(+), 3 deletions(-)
>>
>> diff --git a/lib/librte_vhost/vhost_rxtx.c b/lib/librte_vhost/vhost_rxtx.c
>> index b4da665..859c669 100644
>> --- a/lib/librte_vhost/vhost_rxtx.c
>> +++ b/lib/librte_vhost/vhost_rxtx.c
>> @@ -315,7 +315,7 @@ virtio_dev_rx(struct virtio_net *dev, uint16_t queue_id,
>> rte_prefetch0(&vq->desc[desc_indexes[i+1]]);
>> }
>>
>> - rte_compiler_barrier();
>> + rte_smp_wmb();
>>
>> /* Wait until it's our turn to add our buffer to the used ring. */
>> while (unlikely(vq->last_used_idx != res_start_idx))
>> @@ -565,7 +565,7 @@ virtio_dev_merge_rx(struct virtio_net *dev, uint16_t queue_id,
>>
>> nr_used = copy_mbuf_to_desc_mergeable(dev, vq, start, end,
>> pkts[pkt_idx]);
>> - rte_compiler_barrier();
>> + rte_smp_wmb();
>>
>> /*
>> * Wait until it's our turn to add our buffer
>> @@ -923,7 +923,8 @@ rte_vhost_dequeue_burst(struct virtio_net *dev, uint16_t queue_id,
>> sizeof(vq->used->ring[used_idx]));
>> }
>>
>> - rte_compiler_barrier();
>> + rte_smp_wmb();
>> + rte_smp_rmb();
>
> rte_smp_mb?
rte_smp_mb() is a real mm_fence() on x86. And we don't need to synchronize reads with
writes here, only reads with reads and writes with writes. It is enough because next
increment uses read and write. Pair of barriers is better because it will not impact
on performance on x86.
Best regards, Ilya Maximets.
next prev parent reply other threads:[~2016-03-21 4:49 UTC|newest]
Thread overview: 28+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-02-24 11:47 [dpdk-dev] [PATCH RFC v3 0/3] Thread safe rte_vhost_enqueue_burst() Ilya Maximets
2016-02-24 11:47 ` [dpdk-dev] [PATCH RFC v3 1/3] vhost: use SMP barriers instead of compiler ones Ilya Maximets
2016-03-18 10:08 ` Xie, Huawei
2016-03-18 10:23 ` Ilya Maximets
2016-03-18 10:27 ` Xie, Huawei
2016-03-18 10:39 ` Ilya Maximets
2016-03-18 10:47 ` Xie, Huawei
2016-03-18 11:00 ` Ilya Maximets
[not found] ` <C37D651A908B024F974696C65296B57B4C67825C@SHSMSX101.ccr.corp.intel.com>
[not found] ` <56EBE9AE.9070400@samsung.com>
[not found] ` <56EBF256.8040409@samsung.com>
2016-03-18 12:28 ` Ilya Maximets
2016-03-18 12:23 ` [dpdk-dev] [PATCH v4] " Ilya Maximets
2016-03-18 12:41 ` Yuanhan Liu
2016-03-21 4:49 ` Ilya Maximets [this message]
2016-03-21 14:07 ` Ananyev, Konstantin
2016-03-21 17:25 ` Xie, Huawei
2016-03-21 17:36 ` Ananyev, Konstantin
2016-03-23 14:07 ` Xie, Huawei
2016-03-31 13:46 ` Thomas Monjalon
2016-02-24 11:47 ` [dpdk-dev] [PATCH RFC v3 2/3] vhost: make buf vector for scatter RX local Ilya Maximets
2016-02-24 11:47 ` [dpdk-dev] [PATCH RFC v3 3/3] vhost: avoid reordering of used->idx and last_used_idx updating Ilya Maximets
2016-03-17 15:29 ` [dpdk-dev] [PATCH RFC v3 0/3] Thread safe rte_vhost_enqueue_burst() Thomas Monjalon
2016-03-18 8:00 ` Yuanhan Liu
2016-03-18 8:09 ` Thomas Monjalon
2016-03-18 9:16 ` Yuanhan Liu
2016-03-18 9:34 ` Thomas Monjalon
2016-03-18 9:46 ` Yuanhan Liu
2016-03-18 9:55 ` Ilya Maximets
2016-03-18 10:10 ` Xie, Huawei
2016-03-18 10:24 ` Thomas Monjalon
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