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AJvYcCXM1muf8ceBioeDdf4LffGcBnm517DlVl/ISjTPxP9h8Vo/kDF7dgTpKV0Rd9GnMQwOqB6x/zxsT/fXWJGHmbVLWao= X-Gm-Message-State: AOJu0YwyklMkLLA+2F5aoYCUzQ0OGqvrpT3XxU3C8gVE6GOioKjZDM7J 0m7KoQJacSEPEE1iJ1e06PLpQ7qVZEmeyFzQxOtCXiMW+bGARoAzrOd2zVcFG/KNA/2wCw52E8K o+vPs+h8QMpqL1lhhnadQsiUx9NqKclGB5cmo X-Google-Smtp-Source: AGHT+IFuN0O+kal72+FcB0c5JiyRdueE3ZMGP21IEEO1SX378ULBlZj/S+2MBo6xoRWpY8nLXB1udHE0ojkh+LOy+OI= X-Received: by 2002:a05:6000:1a4e:b0:361:78c8:2eb6 with SMTP id ffacd0b85a97d-366e9499ca1mr7618385f8f.25.1719361149918; Tue, 25 Jun 2024 17:19:09 -0700 (PDT) MIME-Version: 1.0 References: <20240624163348.1751454-1-jiaqiyan@google.com> <20240624163348.1751454-5-jiaqiyan@google.com> <78857a6a-f9a2-4072-b2d4-82fcfda25d2d@infradead.org> In-Reply-To: <78857a6a-f9a2-4072-b2d4-82fcfda25d2d@infradead.org> From: Jiaqi Yan Date: Tue, 25 Jun 2024 17:18:56 -0700 Message-ID: Subject: Re: [PATCH v5 4/4] docs: mm: add enable_soft_offline sysctl To: Randy Dunlap Cc: nao.horiguchi@gmail.com, linmiaohe@huawei.com, jane.chu@oracle.com, ioworker0@gmail.com, muchun.song@linux.dev, akpm@linux-foundation.org, shuah@kernel.org, corbet@lwn.net, osalvador@suse.de, rientjes@google.com, duenwen@google.com, fvdl@google.com, linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-doc@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: CF70E1C001A X-Stat-Signature: 7ij8hgc93t61thts15b1msfswmpixmob X-HE-Tag: 1719361151-476034 X-HE-Meta: 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 XSnNJI+S USYBycCZ+Dp8XHBuftOrogTY28yuodyIWSrgua7uGV1O5Rh5vwwmHcoLEzSxywqJOAxKLdLqdx5AZLj4ZtBbgTujRR4fdLR2zjpbgXsfwsePxhjJR5d/1+4lQdL9y2x+kggFEZSWIemvRa0lxpuayDO5+9RGO+ey03Jl9NkPQzq6YfMCb+NqAeARNtzU7/eEswnhlWlif05OMwV7YHQerdvYNOJ8BUek0DQJKl9HH6EicL9lpR5vHV859eJppwZRr4lGpxEb+PtAPOD7krDqm/jgyutnBbsPTNhX4lq/AT0LIumtxXRTf4A/Z747gvXF3n9XAU7cIjhrCFdOGjaFexAz8g8PoUAg5DYO/13ezZRcag7ANluP8etQNrA== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Tue, Jun 25, 2024 at 5:02=E2=80=AFPM Randy Dunlap wrote: > > Hi-- > > On 6/24/24 9:33 AM, Jiaqi Yan wrote: > > Add the documentation for soft offline behaviors / costs, and what > > the new enable_soft_offline sysctl is for. > > > > Acked-by: Oscar Salvador > > > > Signed-off-by: Jiaqi Yan > > --- > > Documentation/admin-guide/sysctl/vm.rst | 32 +++++++++++++++++++++++++ > > 1 file changed, 32 insertions(+) > > > > diff --git a/Documentation/admin-guide/sysctl/vm.rst b/Documentation/ad= min-guide/sysctl/vm.rst > > index e86c968a7a0e..71463a7b3e2a 100644 > > --- a/Documentation/admin-guide/sysctl/vm.rst > > +++ b/Documentation/admin-guide/sysctl/vm.rst > > @@ -267,6 +268,37 @@ used:: > > These are informational only. They do not mean that anything is wrong > > with your system. To disable them, echo 4 (bit 2) into drop_caches. > > > > +enable_soft_offline > > +=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > +Correctable memory errors are very common on servers. Soft-offline is = kernel's > > +solution for memory pages having (excessive) corrected memory errors. > > + > > +For different types of page, soft-offline has different behaviors / co= sts. > > +- For a raw error page, soft-offline migrates the in-use page's conten= t to > > + a new raw page. > > +- For a page that is part of a transparent hugepage, soft-offline spl= its the > > Use only one space after the comma ...................^ > > > + transparent hugepage into raw pages, then migrates only the raw erro= r page. > > + As a result, user is transparently backed by 1 less hugepage, impact= ing > > + memory access performance. > > +- For a page that is part of a HugeTLB hugepage, soft-offline first mi= grates > > + the entire HugeTLB hugepage, during which a free hugepage will be co= nsumed > > + as migration target. Then the original hugepage is dissolved into r= aw > > + pages without compensation, reducing the capacity of the HugeTLB poo= l by 1. > > + > > +It is user's call to choose between reliability (staying away from fra= gile > > +physical memory) vs performance / capacity implications in transparent= and > > +HugeTLB cases. > > + > > +For all architectures, enable_soft_offline controls whether to soft of= fline > > +memory pages. When setting to 1, kernel attempts to soft offline the = pages > > When set to 1, > > > +whenever it thinks needed. When setting to 0, kernel returns EOPNOTSU= PP to > > When set to 0, Thanks Randy! I will fix these 3 nits in v6. > > > +the request to soft offline the pages. Its default value is 1. > > + > > +It is worth mentioning that after setting enable_soft_offline to 0, th= e > > +following requests to soft offline pages will not be performed: > > +- Request to soft offline pages from RAS Correctable Errors Collector. > > +- On ARM, the request to soft offline pages from GHES driver. > > +- On PARISC, the request to soft offline pages from Page Deallocation = Table. > > > > extfrag_threshold > > =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D > > -- > ~Randy