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Date:   Mon, 25 Jan 2021 19:16:19 -0400
From:   Jason Gunthorpe <jgg@ziepe.ca>
To:     "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
Cc:     "Wangzhou (B)" <wangzhou1@hisilicon.com>,
        Greg Kroah-Hartman <gregkh@linuxfoundation.org>,
        Arnd Bergmann <arnd@arndb.de>,
        Zhangfei Gao <zhangfei.gao@linaro.org>,
        "linux-accelerators@lists.ozlabs.org" 
        <linux-accelerators@lists.ozlabs.org>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "iommu@lists.linux-foundation.org" <iommu@lists.linux-foundation.org>,
        "linux-mm@kvack.org" <linux-mm@kvack.org>,
        "Liguozhu (Kenneth)" <liguozhu@hisilicon.com>,
        "chensihang (A)" <chensihang1@hisilicon.com>
Subject: Re: [RFC PATCH v2] uacce: Add uacce_ctrl misc device
Message-ID: <20210125231619.GY4605@ziepe.ca>
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On Mon, Jan 25, 2021 at 10:21:14PM +0000, Song Bao Hua (Barry Song) wrote:
> mlock, while certainly be able to prevent swapping out, it won't
> be able to stop page moving due to:
> * memory compaction in alloc_pages()
> * making huge pages
> * numa balance
> * memory compaction in CMA

Enabling those things is a major reason to have SVA device in the
first place, providing a SW API to turn it all off seems like the
wrong direction.

If the device doesn't want to use SVA then don't use it, use normal
DMA pinning like everything else.

Jason