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AJvYcCVxGgVth6hmDBsLLW8dvwrMk2kXQA5AV1eyHBCCvbGF0V+8UtLilDlsATKW3HqVCN0mYt8ZuTSnKA==@kvack.org X-Gm-Message-State: AOJu0YwX5A9YCfGrc+twNM9vJDTR/PZQ2owEPMer45Yz8sr6/XxQODiX IRX0LC6LJqTeXR/d6UlNFcFFsjF3O9xWogK4YQ77bseCvpQSnoYxl272DkAU8J4WV4y089haQch G3O840djKhVS7M9IVNdJUQgg94FT3pYCJPE76+pEzuQ== X-Gm-Gg: AY/fxX7Yt+bUhjH+4y72k46ZXC2apovR+U20/B29i5jqXUt+EDf6v3TWhvTrpismVpo LiMHlvwpjrblGfUu3lvX1igAM8Lxc6vLknC5OsdVTLm0kgdjzeqJPww8MNhOF/IDW+N2MSiJF05 DuXs67DXO3PX6Hn1GHYMzuN0RIJQTRRm4BYCzVmGEm0Xg2OvMsV1qI91cQA4QdDnR54HP1l+RDc AwDfczPiLEF4iohFfvSX/cIBbEF9fzKfts20292XxkUCKHJwGxMy4srGzyBgX2MYUT3KRE1F8gA J/a00CuQ1ejTGuoufvJ6JLvP X-Google-Smtp-Source: AGHT+IF8hUf/njs47ssOWxWrTAtN9SW44kkMcdwp9wLrZso0GjDwC7fAR8uTmXjFxwWpMLXPrdui4riC4+4Ir5L8T5c= X-Received: by 2002:a17:907:3f21:b0:b76:f57a:b0a7 with SMTP id a640c23a62f3a-b7d238caf7dmr1725050066b.31.1765900354456; Tue, 16 Dec 2025 07:52:34 -0800 (PST) MIME-Version: 1.0 References: <20251216084913.86342-1-epetron@amazon.de> In-Reply-To: From: Pasha Tatashin Date: Tue, 16 Dec 2025 10:51:57 -0500 X-Gm-Features: AQt7F2oVU79Y7RmiV1TRfmRsHfWXG1IqX56Yslo2Aowm0vb9rvseAzO_YZsWkZw Message-ID: Subject: Re: [PATCH] kho: add support for deferred struct page init To: Mike Rapoport Cc: Evangelos Petrongonas , Pratyush Yadav , Alexander Graf , Andrew Morton , Jason Miu , linux-kernel@vger.kernel.org, kexec@lists.infradead.org, linux-mm@kvack.org, nh-open-source@amazon.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: 6BF2580007 X-Rspamd-Server: rspam03 X-Stat-Signature: a8rjuwtito34qgc9amedhhziyoo6yfcm X-Rspam-User: X-HE-Tag: 1765900356-605921 X-HE-Meta: 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 wKRHu7NQ fp/madWPl5bWmo4iWxsw05YqWV4+siy+erx0Aye2J6CKaaoOAtY8Wk5MQ82fYHXzx17Q6Q23XeMhMxX9ErfjCMphxieEJC1Sp4Oe8h8AW/aOJvvBLQ4T6O2c8e2FFKH40GGyCG7T75ovcyDdHrbOsDZ9HTYEt4zoK3MMhf1ix+b5TKDOv1N6B+mR4v6l4AmY5rsoqd2KHbvf2xbu1sU0Vg8M6Irs/T+QYeNdhBtBmk3JgSNbBVZq0MSJCIMVY1BNkTFkA1eXGf6+6Uotl+LwdgBFItA== 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, Dec 16, 2025 at 10:36=E2=80=AFAM Pasha Tatashin wrote: > > On Tue, Dec 16, 2025 at 10:19=E2=80=AFAM Mike Rapoport = wrote: > > > > On Tue, Dec 16, 2025 at 10:05:27AM -0500, Pasha Tatashin wrote: > > > > > +static struct page *__init kho_get_preserved_page(phys_addr_t ph= ys, > > > > > + unsigned int orde= r) > > > > > +{ > > > > > + unsigned long pfn =3D PHYS_PFN(phys); > > > > > + int nid =3D early_pfn_to_nid(pfn); > > > > > + > > > > > + for (int i =3D 0; i < (1 << order); i++) > > > > > + init_deferred_page(pfn + i, nid); > > > > > > > > This will skip pages below node->first_deferred_pfn, we need to use > > > > __init_page_from_nid() here. > > > > > > Mike, but those struct pages should be initialized early anyway. If > > > they are not yet initialized we have a problem, as they are going to > > > be re-initialized later. > > > > Can say I understand your point. Which pages should be initialized earl= t? > > All pages below node->first_deferred_pfn. > > > And which pages will be reinitialized? > > kho_memory_init() is called after free_area_init() (which calls > memmap_init_range to initialize low memory struct pages). So, if we > use __init_page_from_nid() as suggested, we would be blindly running > __init_single_page() again on those low-memory pages that > memmap_init_range() already set up. This would cause double > initialization and corruptions due to losing the order information. > > > > > > + > > > > > + return pfn_to_page(pfn); > > > > > +} > > > > > + > > > > > static void __init deserialize_bitmap(unsigned int order, > > > > > struct khoser_mem_bitmap_ptr = *elm) > > > > > { > > > > > @@ -449,7 +466,7 @@ static void __init deserialize_bitmap(unsigne= d int order, > > > > > int sz =3D 1 << (order + PAGE_SHIFT); > > > > > phys_addr_t phys =3D > > > > > elm->phys_start + (bit << (order + PAGE_SHI= FT)); > > > > > - struct page *page =3D phys_to_page(phys); > > > > > + struct page *page =3D kho_get_preserved_page(phys, = order); > > > > > > > > I think it's better to initialize deferred struct pages later in > > > > kho_restore_page. deserialize_bitmap() runs before SMP and it alrea= dy does > > > > > > The KHO memory should still be accessible early in boot, right? > > > > The memory is accessible. And we anyway should not use struct page for > > preserved memory before kho_restore_{folio,pages}. > > This makes sense, what happens if someone calls kho_restore_folio() > before deferred pages are initialized? I looked at your repo. I think what you're proposing makes sense, and indeed it will provide a performance boost if some of the folios are restored in parallel. Just kho_init_deferred_pages() should be using init_deferred_page() to avoid re-initializing the lower memory pages. Also, I am still wondering how it will work with HVO, but I need to take a look at Pratyuh's series for that. Thanks, Pasha