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

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Message-ID: <20210210185052.GE308988@casper.infradead.org>
Date:   Wed, 10 Feb 2021 18:50:52 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     Zhou Wang <wangzhou1@...ilicon.com>
Cc:     Greg KH <gregkh@...uxfoundation.org>,
        Andy Lutomirski <luto@...capital.net>,
        linux-kernel@...r.kernel.org, iommu@...ts.linux-foundation.org,
        linux-mm@...ck.org, linux-arm-kernel@...ts.infradead.org,
        linux-api@...r.kernel.org,
        Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        song.bao.hua@...ilicon.com, jgg@...pe.ca, kevin.tian@...el.com,
        jean-philippe@...aro.org, eric.auger@...hat.com,
        liguozhu@...ilicon.com, zhangfei.gao@...aro.org,
        Sihang Chen <chensihang1@...ilicon.com>
Subject: Re: [RFC PATCH v3 1/2] mempinfd: Add new syscall to provide memory
 pin

On Tue, Feb 09, 2021 at 08:20:18PM +0800, Zhou Wang wrote:
> Agree, will add it in next version.

No, don't do another version.  Jason is right, this approach is wrong.
The point of SVA is that it doesn't require the application to do
anything special.  If jitter from too-frequent page migration is actually
a problem, then fix the frequency of page migration.  Don't pretend that
this particular application is so important that it prevents the kernel
from doing its housekeeping.