From: Matthew Wilcox <willy@infradead.org>
To: "Song Bao Hua (Barry Song)" <song.bao.hua@hisilicon.com>
Cc: "jean-philippe@linaro.org" <jean-philippe@linaro.org>,
"kevin.tian@intel.com" <kevin.tian@intel.com>,
"chensihang \(A\)" <chensihang1@hisilicon.com>,
"jgg@ziepe.ca" <jgg@ziepe.ca>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.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>,
"Wangzhou \(B\)" <wangzhou1@hisilicon.com>,
Alexander Viro <viro@zeniv.linux.org.uk>,
"eric.auger@redhat.com" <eric.auger@redhat.com>,
"gregkh@linuxfoundation.org" <gregkh@linuxfoundation.org>,
"zhangfei.gao@linaro.org" <zhangfei.gao@linaro.org>,
Andrew Morton <akpm@linux-foundation.org>,
"Liguozhu \(Kenneth\)" <liguozhu@hisilicon.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>
Subject: Re: [RFC PATCH v3 1/2] mempinfd: Add new syscall to provide memory pin
Date: Mon, 8 Feb 2021 01:30:56 +0000 [thread overview]
Message-ID: <20210208013056.GM308988@casper.infradead.org> (raw)
In-Reply-To: <f4b2d7db8a1047d9952cbbfaf9e27824@hisilicon.com>
On Sun, Feb 07, 2021 at 10:24:28PM +0000, Song Bao Hua (Barry Song) wrote:
> > > In high-performance I/O cases, accelerators might want to perform
> > > I/O on a memory without IO page faults which can result in dramatically
> > > increased latency. Current memory related APIs could not achieve this
> > > requirement, e.g. mlock can only avoid memory to swap to backup device,
> > > page migration can still trigger IO page fault.
> >
> > Well ... we have two requirements. The application wants to not take
> > page faults. The system wants to move the application to a different
> > NUMA node in order to optimise overall performance. Why should the
> > application's desires take precedence over the kernel's desires? And why
> > should it be done this way rather than by the sysadmin using numactl to
> > lock the application to a particular node?
>
> NUMA balancer is just one of many reasons for page migration. Even one
> simple alloc_pages() can cause memory migration in just single NUMA
> node or UMA system.
>
> The other reasons for page migration include but are not limited to:
> * memory move due to CMA
> * memory move due to huge pages creation
>
> Hardly we can ask users to disable the COMPACTION, CMA and Huge Page
> in the whole system.
You're dodging the question. Should the CMA allocation fail because
another application is using SVA?
I would say no. The application using SVA should take the one-time
performance hit from having its memory moved around.
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next prev parent reply other threads:[~2021-02-08 1:32 UTC|newest]
Thread overview: 33+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-02-07 8:18 [RFC PATCH v3 0/2] mempinfd: Add new syscall to provide memory pin Zhou Wang
2021-02-07 8:18 ` [RFC PATCH v3 1/2] " Zhou Wang
2021-02-07 21:34 ` Matthew Wilcox
2021-02-07 22:24 ` Song Bao Hua (Barry Song)
2021-02-08 1:30 ` Matthew Wilcox [this message]
2021-02-08 2:27 ` Song Bao Hua (Barry Song)
2021-02-08 8:21 ` David Hildenbrand
2021-02-08 10:13 ` Song Bao Hua (Barry Song)
2021-02-08 10:37 ` David Hildenbrand
2021-02-08 20:52 ` Song Bao Hua (Barry Song)
2021-02-08 2:18 ` David Rientjes
2021-02-08 5:34 ` Song Bao Hua (Barry Song)
2021-02-09 9:02 ` Zhou Wang
2021-02-07 21:51 ` Arnd Bergmann
2021-02-09 9:27 ` Zhou Wang
2021-02-07 22:02 ` Andy Lutomirski
2021-02-09 9:17 ` Zhou Wang
2021-02-09 9:37 ` Greg KH
2021-02-09 11:58 ` Zhou Wang
2021-02-09 12:01 ` Greg KH
2021-02-09 12:20 ` Zhou Wang
2021-02-10 18:50 ` Matthew Wilcox
2021-02-08 8:14 ` David Hildenbrand
2021-02-08 18:33 ` Jason Gunthorpe
2021-02-08 20:35 ` Song Bao Hua (Barry Song)
2021-02-08 21:30 ` Jason Gunthorpe
2021-02-09 3:01 ` Song Bao Hua (Barry Song)
2021-02-09 13:53 ` Jason Gunthorpe
2021-02-09 22:22 ` Song Bao Hua (Barry Song)
2021-02-10 18:04 ` Jason Gunthorpe
2021-02-10 21:39 ` Song Bao Hua (Barry Song)
2021-02-11 10:28 ` David Hildenbrand
2021-02-07 8:18 ` [RFC PATCH v3 2/2] selftests/vm: add mempinfd test Zhou Wang
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