linux-kernel - Re: [RFC PATCH v3 1/2] mempinfd: Add new syscall to provide memory pin

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Message-ID: <20210209135331.GF4718@ziepe.ca>
Date:   Tue, 9 Feb 2021 09:53:31 -0400
From:   Jason Gunthorpe <jgg@...pe.ca>
To:     "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>
Cc:     David Hildenbrand <david@...hat.com>,
        "Wangzhou (B)" <wangzhou1@...ilicon.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "iommu@...ts.linux-foundation.org" <iommu@...ts.linux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-arm-kernel@...ts.infradead.org" 
        <linux-arm-kernel@...ts.infradead.org>,
        "linux-api@...r.kernel.org" <linux-api@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        "gregkh@...uxfoundation.org" <gregkh@...uxfoundation.org>,
        "kevin.tian@...el.com" <kevin.tian@...el.com>,
        "jean-philippe@...aro.org" <jean-philippe@...aro.org>,
        "eric.auger@...hat.com" <eric.auger@...hat.com>,
        "Liguozhu (Kenneth)" <liguozhu@...ilicon.com>,
        "zhangfei.gao@...aro.org" <zhangfei.gao@...aro.org>,
        "chensihang (A)" <chensihang1@...ilicon.com>
Subject: Re: [RFC PATCH v3 1/2] mempinfd: Add new syscall to provide memory
 pin

On Tue, Feb 09, 2021 at 03:01:42AM +0000, Song Bao Hua (Barry Song) wrote:

> On the other hand, wouldn't it be the benefit of hardware accelerators
> to have a lower and more stable latency zip/encryption than CPU?

No, I don't think so.

If this is an important problem then it should apply equally to CPU
and IO jitter.

Honestly I find the idea that occasional migration jitters CPU and DMA
to not be very compelling. Such specialized applications should
allocate special pages to avoid this, not adding an API to be able to
lock down any page
 
Jason