DPDK patches and discussions
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From: "Tan, Jianfeng" <jianfeng.tan@intel.com>
To: Yuanhan Liu <yuanhan.liu@linux.intel.com>
Cc: dev@dpdk.org, huawei.xie@intel.com
Subject: Re: [dpdk-dev] [PATCH] virtio: fix allocating virtnet_rx not mem aligned
Date: Mon, 13 Jun 2016 18:15:29 +0800	[thread overview]
Message-ID: <d120e623-041f-4689-5cf3-9ff171880e8f@intel.com> (raw)
In-Reply-To: <20160613092101.GN10038@yliu-dev.sh.intel.com>



On 6/13/2016 5:21 PM, Yuanhan Liu wrote:
> On Sun, Jun 12, 2016 at 02:29:42PM +0000, Jianfeng Tan wrote:
>> Compile DPDK with clang, below line in virtio_rxtx.c could be
>> optimized with four "VMOVAPS ymm, m256".
>>    memset(&rxvq->fake_mbuf, 0, sizeof(rxvq->fake_mbuf));
>>
>> This instruction requires memory address is 32-byte aligned.
>> Or, it leads to segfault.
> That looks like a dangerous optimization to me.If that's the case,
> doesn't it mean we have to make sure the address is always aligned
> properly while calling memset?

I guess clang does such optimization when length is a 32-byte aligned 
immediate number. May need more information here.

Thanks,
Jianfeng

>
> 	--yliu

  parent reply	other threads:[~2016-06-13 10:15 UTC|newest]

Thread overview: 7+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-06-12 14:29 Jianfeng Tan
2016-06-13  9:21 ` Yuanhan Liu
2016-06-13  9:51   ` Yuanhan Liu
2016-06-13 10:06     ` Tan, Jianfeng
2016-06-13 10:26       ` Yuanhan Liu
2016-06-13 10:15   ` Tan, Jianfeng [this message]
2016-06-14 12:44 ` Yuanhan Liu

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