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AJvYcCVwq91oJBAb7xFO8FJrjd/2fsexoVP+1EoH+IngkSu4vz0bs7nNJOqbVRh02mvQD/YgrPE/2afkcg==@kvack.org X-Gm-Message-State: AOJu0YwWh9tcW9wzHfhSQjmXrEaMDCNXmGn0jcCk5NL6ISe35zqJYdzM 08rh6UcM3hKInHJLWEs2FpERLT54HoD4cKSixT5mYKGpsI/D4dyiK1mJ2jZ5Us86GEk4XbmvbqI gWw5htDZTdj1H0KQiXRVa0X0SY2vssVsGsjsah4UC X-Gm-Gg: ATEYQzy632wOmZCY9u80mlcUU81CL6+m1OpIDOs19E2HRwiEkKBIMKRHxGbvdJ46rFK UdydW05Hzuo1dmFiCWW6xBuR9w7niadOzXkh23Ksc1+gvdg3IBgWQSc5td3myZ9sRHnkKWIm6lH i3hAQ+uiVJdHtvhQcs9C3RQKZMjMsdLeGwUfhUDO7tRVnIbyhPtBRlrrqVS+N98kF30Ep8WbxQq 23VKRin3kru+054H3Kn55Kb7zc8fA7Jwk9l4sucqrBhnm8mXvrOyqX/kDCUttz53atyItTU+PLI WykKHRq/Tpvgbx8U9JQr2zBH1NszZG9DQsm4KQ== X-Received: by 2002:a05:622a:a09:b0:4ff:c0e7:be9c with SMTP id d75a77b69052e-50b938bd25bmr5574351cf.0.1774501454155; Wed, 25 Mar 2026 22:04:14 -0700 (PDT) MIME-Version: 1.0 References: <20260319083153.2488005-1-hao.ge@linux.dev> <20260319152808.fce61386fdf2934d7a3b0edb@linux-foundation.org> <9ef1c798-a30f-4458-9684-900136ae8b7d@linux.dev> <575e727e-cd47-41df-966a-142425aa8a8b@linux.dev> <35d274d9-ed52-4325-80fb-c374e8af3169@linux.dev> <88c6ac9d-d966-4c25-b16d-6808f9e8c43a@linux.dev> <098f53cc-97b5-4647-89dd-0e5820b1e9a0@linux.dev> In-Reply-To: <098f53cc-97b5-4647-89dd-0e5820b1e9a0@linux.dev> From: Suren Baghdasaryan Date: Wed, 25 Mar 2026 22:04:02 -0700 X-Gm-Features: AQROBzA19cPCQ17GKwmURTR9x7R1tQip_MIHi6B7h5ULrzxoif8aLcuyT196Mt0 Message-ID: Subject: Re: [PATCH] mm/alloc_tag: clear codetag for pages allocated before page_ext initialization To: Hao Ge Cc: Andrew Morton , Kent Overstreet , linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam11 X-Rspamd-Queue-Id: DF97620008 X-Stat-Signature: ojwtfkrmwi4eiktetqreby397tmxfe8t X-HE-Tag: 1774501455-714435 X-HE-Meta: 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 iAePSBii yOKWppY09QsetgpQyDLZYqRaZizdI1GFzIkTLFVtAIFPvqjazSebXMhr2iO3uYUuQH/wN1GjvoN4KP9u0w78FBaxWu/GMOlbwpsqOJXsF0Y+h4uzb3hT0bC8GS9nmsTefm2E/AjChD25cPvbrVUXrNQfv7cKQLdRG7S5kTu348O28G6hznfbzso5ZHNCD+ObOp+3xUDYO8/V0d9SqrlbfZlcF04N4RG3UbU29XCNDI8HQj9RF9EI7aR6SIrxHDN2djGFRwtwz6UQKKpstwKyqu5hD+YdpH6uD718z7sxVTQy806iqsMYiS0xpJtt3MtLT/WKy+poH9m9yqOZyh/+Jt5H+pl9wbj0f/vw3RKxnkYty9UqrZBiTw864pky2AzJeOw0uAjqqNLHDlYxrgIvNXJZ5G+DDBWDvsdM/LYzpRVY70qVaVtiPj12sJuQfjug3tQIDfRylAhyIJY9FGY5f9e+HcaVvjtmzUkLEPEGberCHEoU= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Mar 25, 2026 at 6:45=E2=80=AFPM Hao Ge wrote: > > > On 2026/3/25 23:17, Suren Baghdasaryan wrote: > > On Wed, Mar 25, 2026 at 4:21=E2=80=AFAM Hao Ge wrote= : > >> > >> On 2026/3/25 15:35, Suren Baghdasaryan wrote: > >>> On Tue, Mar 24, 2026 at 11:25=E2=80=AFPM Suren Baghdasaryan wrote: > >>>> On Tue, Mar 24, 2026 at 7:08=E2=80=AFPM Hao Ge wr= ote: > >>>>> On 2026/3/25 08:21, Suren Baghdasaryan wrote: > >>>>>> On Tue, Mar 24, 2026 at 2:43=E2=80=AFAM Hao Ge = wrote: > >>>>>>> On 2026/3/24 06:47, Suren Baghdasaryan wrote: > >>>>>>>> On Mon, Mar 23, 2026 at 2:16=E2=80=AFAM Hao Ge wrote: > >>>>>>>>> On 2026/3/20 10:14, Suren Baghdasaryan wrote: > >>>>>>>>>> On Thu, Mar 19, 2026 at 6:58=E2=80=AFPM Hao Ge wrote: > >>>>>>>>>>> On 2026/3/20 07:48, Suren Baghdasaryan wrote: > >>>>>>>>>>>> On Thu, Mar 19, 2026 at 4:44=E2=80=AFPM Suren Baghdasaryan <= surenb@google.com> wrote: > >>>>>>>>>>>>> On Thu, Mar 19, 2026 at 3:28=E2=80=AFPM Andrew Morton wrote: > >>>>>>>>>>>>>> On Thu, 19 Mar 2026 16:31:53 +0800 Hao Ge wrote: > >>>>>>>>>>>>>> > >>>>>>>>>>>>>>> Due to initialization ordering, page_ext is allocated and= initialized > >>>>>>>>>>>>>>> relatively late during boot. Some pages have already been= allocated > >>>>>>>>>>>>>>> and freed before page_ext becomes available, leaving thei= r codetag > >>>>>>>>>>>>>>> uninitialized. > >>>>>>>>>>>>> Hi Hao, > >>>>>>>>>>>>> Thanks for the report. > >>>>>>>>>>>>> Hmm. So, we are allocating pages before page_ext is initial= ized... > >>>>>>>>>>>>> > >>>>>>>>>>>>>>> A clear example is in init_section_page_ext(): alloc_page= _ext() calls > >>>>>>>>>>>>>>> kmemleak_alloc(). > >>>>>>>>>>>> Forgot to ask. The example you are using here is for page_ex= t > >>>>>>>>>>>> allocation itself. Do you have any other examples where page > >>>>>>>>>>>> allocation happens before page_ext initialization? If that's= the only > >>>>>>>>>>>> place, then we might be able to fix this in a simpler way by= doing > >>>>>>>>>>>> something special for alloc_page_ext(). > >>>>>>>>>>> Hi Suren > >>>>>>>>>>> > >>>>>>>>>>> To help illustrate the point, here's the debug log I added: > >>>>>>>>>>> > >>>>>>>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c > >>>>>>>>>>> index 2d4b6f1a554e..ebfe636f5b07 100644 > >>>>>>>>>>> --- a/mm/page_alloc.c > >>>>>>>>>>> +++ b/mm/page_alloc.c > >>>>>>>>>>> @@ -1293,6 +1293,9 @@ void __pgalloc_tag_add(struct page *pag= e, struct > >>>>>>>>>>> task_struct *task, > >>>>>>>>>>> alloc_tag_add(&ref, task->alloc_tag, PA= GE_SIZE * nr); > >>>>>>>>>>> update_page_tag_ref(handle, &ref); > >>>>>>>>>>> put_page_tag_ref(handle); > >>>>>>>>>>> + } else { > >>>>>>>>>>> + pr_warn("__pgalloc_tag_add: get_page_tag_ref = failed! > >>>>>>>>>>> page=3D%p pfn=3D%lu nr=3D%u\n", page, page_to_pfn(page), nr); > >>>>>>>>>>> + dump_stack(); > >>>>>>>>>>> } > >>>>>>>>>>> } > >>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>> And I caught the following logs: > >>>>>>>>>>> > >>>>>>>>>>> [ 0.296399] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>>>>>> page=3Dffffea000400c700 pfn=3D1049372 nr=3D1 > >>>>>>>>>>> [ 0.296400] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not taint= ed > >>>>>>>>>>> 7.0.0-rc4-dirty #12 PREEMPT(lazy) > >>>>>>>>>>> [ 0.296402] Hardware name: Red Hat KVM, BIOS > >>>>>>>>>>> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > >>>>>>>>>>> [ 0.296402] Call Trace: > >>>>>>>>>>> [ 0.296403] > >>>>>>>>>>> [ 0.296403] dump_stack_lvl+0x53/0x70 > >>>>>>>>>>> [ 0.296405] __pgalloc_tag_add+0x3a3/0x6e0 > >>>>>>>>>>> [ 0.296406] ? __pfx___pgalloc_tag_add+0x10/0x10 > >>>>>>>>>>> [ 0.296407] ? kasan_unpoison+0x27/0x60 > >>>>>>>>>>> [ 0.296409] ? __kasan_unpoison_pages+0x2c/0x40 > >>>>>>>>>>> [ 0.296411] get_page_from_freelist+0xa54/0x1310 > >>>>>>>>>>> [ 0.296413] __alloc_frozen_pages_noprof+0x206/0x4c0 > >>>>>>>>>>> [ 0.296415] ? __pfx___alloc_frozen_pages_noprof+0x10/0x10 > >>>>>>>>>>> [ 0.296417] ? stack_depot_save_flags+0x3f/0x680 > >>>>>>>>>>> [ 0.296418] ? ___slab_alloc+0x518/0x530 > >>>>>>>>>>> [ 0.296420] alloc_pages_mpol+0x13a/0x3f0 > >>>>>>>>>>> [ 0.296421] ? __pfx_alloc_pages_mpol+0x10/0x10 > >>>>>>>>>>> [ 0.296423] ? _raw_spin_lock_irqsave+0x8a/0xf0 > >>>>>>>>>>> [ 0.296424] ? __pfx__raw_spin_lock_irqsave+0x10/0x10 > >>>>>>>>>>> [ 0.296426] alloc_slab_page+0xc2/0x130 > >>>>>>>>>>> [ 0.296427] allocate_slab+0x77/0x2c0 > >>>>>>>>>>> [ 0.296429] ? syscall_enter_define_fields+0x3bb/0x5f0 > >>>>>>>>>>> [ 0.296430] ___slab_alloc+0x125/0x530 > >>>>>>>>>>> [ 0.296432] ? __trace_define_field+0x252/0x3d0 > >>>>>>>>>>> [ 0.296433] __kmalloc_noprof+0x329/0x630 > >>>>>>>>>>> [ 0.296435] ? syscall_enter_define_fields+0x3bb/0x5f0 > >>>>>>>>>>> [ 0.296436] syscall_enter_define_fields+0x3bb/0x5f0 > >>>>>>>>>>> [ 0.296438] ? __pfx_syscall_enter_define_fields+0x10/0x10 > >>>>>>>>>>> [ 0.296440] event_define_fields+0x326/0x540 > >>>>>>>>>>> [ 0.296441] __trace_early_add_events+0xac/0x3c0 > >>>>>>>>>>> [ 0.296443] trace_event_init+0x24c/0x460 > >>>>>>>>>>> [ 0.296445] trace_init+0x9/0x20 > >>>>>>>>>>> [ 0.296446] start_kernel+0x199/0x3c0 > >>>>>>>>>>> [ 0.296448] x86_64_start_reservations+0x18/0x30 > >>>>>>>>>>> [ 0.296449] x86_64_start_kernel+0xe2/0xf0 > >>>>>>>>>>> [ 0.296451] common_startup_64+0x13e/0x141 > >>>>>>>>>>> [ 0.296453] > >>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>> [ 0.312234] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>>>>>> page=3Dffffea000400f900 pfn=3D1049572 nr=3D1 > >>>>>>>>>>> [ 0.312234] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not taint= ed > >>>>>>>>>>> 7.0.0-rc4-dirty #12 PREEMPT(lazy) > >>>>>>>>>>> [ 0.312236] Hardware name: Red Hat KVM, BIOS > >>>>>>>>>>> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > >>>>>>>>>>> [ 0.312236] Call Trace: > >>>>>>>>>>> [ 0.312237] > >>>>>>>>>>> [ 0.312237] dump_stack_lvl+0x53/0x70 > >>>>>>>>>>> [ 0.312239] __pgalloc_tag_add+0x3a3/0x6e0 > >>>>>>>>>>> [ 0.312240] ? __pfx___pgalloc_tag_add+0x10/0x10 > >>>>>>>>>>> [ 0.312241] ? rmqueue.constprop.0+0x4fc/0x1ce0 > >>>>>>>>>>> [ 0.312243] ? kasan_unpoison+0x27/0x60 > >>>>>>>>>>> [ 0.312244] ? __kasan_unpoison_pages+0x2c/0x40 > >>>>>>>>>>> [ 0.312246] get_page_from_freelist+0xa54/0x1310 > >>>>>>>>>>> [ 0.312248] __alloc_frozen_pages_noprof+0x206/0x4c0 > >>>>>>>>>>> [ 0.312250] ? __pfx___alloc_frozen_pages_noprof+0x10/0x10 > >>>>>>>>>>> [ 0.312253] alloc_slab_page+0x39/0x130 > >>>>>>>>>>> [ 0.312254] allocate_slab+0x77/0x2c0 > >>>>>>>>>>> [ 0.312255] ? alloc_cpumask_var_node+0xc7/0x230 > >>>>>>>>>>> [ 0.312257] ___slab_alloc+0x46d/0x530 > >>>>>>>>>>> [ 0.312259] __kmalloc_node_noprof+0x2fa/0x680 > >>>>>>>>>>> [ 0.312261] ? alloc_cpumask_var_node+0xc7/0x230 > >>>>>>>>>>> [ 0.312263] alloc_cpumask_var_node+0xc7/0x230 > >>>>>>>>>>> [ 0.312264] init_desc+0x141/0x6b0 > >>>>>>>>>>> [ 0.312266] alloc_desc+0x108/0x1b0 > >>>>>>>>>>> [ 0.312267] early_irq_init+0xee/0x1c0 > >>>>>>>>>>> [ 0.312268] ? __pfx_early_irq_init+0x10/0x10 > >>>>>>>>>>> [ 0.312271] start_kernel+0x1ab/0x3c0 > >>>>>>>>>>> [ 0.312272] x86_64_start_reservations+0x18/0x30 > >>>>>>>>>>> [ 0.312274] x86_64_start_kernel+0xe2/0xf0 > >>>>>>>>>>> [ 0.312275] common_startup_64+0x13e/0x141 > >>>>>>>>>>> [ 0.312277] > >>>>>>>>>>> > >>>>>>>>>>> [ 0.312834] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>>>>>> page=3Dffffea000400fc00 pfn=3D1049584 nr=3D1 > >>>>>>>>>>> [ 0.312835] CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not taint= ed > >>>>>>>>>>> 7.0.0-rc4-dirty #12 PREEMPT(lazy) > >>>>>>>>>>> [ 0.312836] Hardware name: Red Hat KVM, BIOS > >>>>>>>>>>> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > >>>>>>>>>>> [ 0.312837] Call Trace: > >>>>>>>>>>> [ 0.312837] > >>>>>>>>>>> [ 0.312838] dump_stack_lvl+0x53/0x70 > >>>>>>>>>>> [ 0.312840] __pgalloc_tag_add+0x3a3/0x6e0 > >>>>>>>>>>> [ 0.312841] ? __pfx___pgalloc_tag_add+0x10/0x10 > >>>>>>>>>>> [ 0.312842] ? rmqueue.constprop.0+0x4fc/0x1ce0 > >>>>>>>>>>> [ 0.312844] ? kasan_unpoison+0x27/0x60 > >>>>>>>>>>> [ 0.312845] ? __kasan_unpoison_pages+0x2c/0x40 > >>>>>>>>>>> [ 0.312847] get_page_from_freelist+0xa54/0x1310 > >>>>>>>>>>> [ 0.312849] __alloc_frozen_pages_noprof+0x206/0x4c0 > >>>>>>>>>>> [ 0.312851] ? __pfx___alloc_frozen_pages_noprof+0x10/0x10 > >>>>>>>>>>> [ 0.312853] alloc_pages_mpol+0x13a/0x3f0 > >>>>>>>>>>> [ 0.312855] ? __pfx_alloc_pages_mpol+0x10/0x10 > >>>>>>>>>>> [ 0.312856] ? xas_find+0x2d8/0x450 > >>>>>>>>>>> [ 0.312858] ? _raw_spin_lock+0x84/0xe0 > >>>>>>>>>>> [ 0.312859] ? __pfx__raw_spin_lock+0x10/0x10 > >>>>>>>>>>> [ 0.312861] alloc_pages_noprof+0xf6/0x2b0 > >>>>>>>>>>> [ 0.312862] __change_page_attr+0x293/0x850 > >>>>>>>>>>> [ 0.312864] ? __pfx___change_page_attr+0x10/0x10 > >>>>>>>>>>> [ 0.312865] ? _vm_unmap_aliases+0x2d0/0x650 > >>>>>>>>>>> [ 0.312868] ? __pfx__vm_unmap_aliases+0x10/0x10 > >>>>>>>>>>> [ 0.312869] __change_page_attr_set_clr+0x16c/0x360 > >>>>>>>>>>> [ 0.312871] ? spp_getpage+0xbb/0x1e0 > >>>>>>>>>>> [ 0.312872] change_page_attr_set_clr+0x220/0x3c0 > >>>>>>>>>>> [ 0.312873] ? flush_tlb_one_kernel+0xf/0x30 > >>>>>>>>>>> [ 0.312875] ? set_pte_vaddr_p4d+0x110/0x180 > >>>>>>>>>>> [ 0.312877] ? __pfx_change_page_attr_set_clr+0x10/0x10 > >>>>>>>>>>> [ 0.312878] ? __pfx_set_pte_vaddr_p4d+0x10/0x10 > >>>>>>>>>>> [ 0.312881] ? __pfx_mtree_load+0x10/0x10 > >>>>>>>>>>> [ 0.312883] ? __pfx_mtree_load+0x10/0x10 > >>>>>>>>>>> [ 0.312884] ? __asan_memcpy+0x3c/0x60 > >>>>>>>>>>> [ 0.312886] ? set_intr_gate+0x10c/0x150 > >>>>>>>>>>> [ 0.312888] set_memory_ro+0x76/0xa0 > >>>>>>>>>>> [ 0.312889] ? __pfx_set_memory_ro+0x10/0x10 > >>>>>>>>>>> [ 0.312891] idt_setup_apic_and_irq_gates+0x2c1/0x390 > >>>>>>>>>>> > >>>>>>>>>>> and more. > >>>>>>>>>> Ok, it's not the only place. Got your point. > >>>>>>>>>> > >>>>>>>>>>> off topic - if we were to handle only alloc_page_ext() speci= fically, > >>>>>>>>>>> what would be the most straightforward > >>>>>>>>>>> > >>>>>>>>>>> solution in your mind? I'd really appreciate your insight. > >>>>>>>>>> I was thinking if it's the only special case maybe we can hand= le it > >>>>>>>>>> somehow differently, like we do when we allocate obj_ext vecto= rs for > >>>>>>>>>> slabs using __GFP_NO_OBJ_EXT. I haven't found a good solution = yet but > >>>>>>>>>> since it's not a special case we would not be able to use it e= ven if I > >>>>>>>>>> came up with something... > >>>>>>>>>> I think your way is the most straight-forward but please try m= y > >>>>>>>>>> suggestion to see if we can avoid extra overhead. > >>>>>>>>>> Thanks, > >>>>>>>>>> Suren. > >>>>> Hi Suren > >>>>>>> Hi Suren > >>>>>>> > >>>>>>> > >>>>>>>> Hi Hao, > >>>>>>>> > >>>>>>>>> Hi Suren > >>>>>>>>> > >>>>>>>>> Thank you for your feedback. After re-examining this issue, > >>>>>>>>> > >>>>>>>>> I realize my previous focus was misplaced. > >>>>>>>>> > >>>>>>>>> Upon deeper consideration, I understand that this is not merely= a bug, > >>>>>>>>> > >>>>>>>>> but rather a warning that indicates a gap in our memory profili= ng mechanism. > >>>>>>>>> > >>>>>>>>> Specifically, the current implementation appears to be missing = memory > >>>>>>>>> allocation > >>>>>>>>> > >>>>>>>>> tracking during the period between the buddy system allocation = and page_ext > >>>>>>>>> > >>>>>>>>> initialization. > >>>>>>>>> > >>>>>>>>> This profiling gap means we may not be capturing all relevant m= emory > >>>>>>>>> allocation > >>>>>>>>> > >>>>>>>>> events during this critical transition phase. > >>>>>>>> Correct, this limitation exists because memory profiling relies = on > >>>>>>>> some kernel facilities (page_ext, objj_ext) which might not be > >>>>>>>> initialized yet at the time of allocation. > >>>>>>>> > >>>>>>>>> My approach is to dynamically allocate codetag_ref when get_pag= e_tag_ref > >>>>>>>>> fails, > >>>>>>>>> > >>>>>>>>> and maintain a linked list to track all buddy system allocation= s that > >>>>>>>>> occur prior to page_ext initialization. > >>>>>>>>> > >>>>>>>>> However, this introduces performance concerns: > >>>>>>>>> > >>>>>>>>> 1. Free Path Overhead: When freeing these pages, we would need = to > >>>>>>>>> traverse the entire linked list to locate > >>>>>>>>> > >>>>>>>>> the corresponding codetag_ref, resulting in O(n) look= up complexity > >>>>>>>>> per free operation. > >>>>>>>>> > >>>>>>>>> 2. Initialization Overhead: During init_page_alloc_tagging, ite= rating > >>>>>>>>> through the linked list to assign codetag_ref to > >>>>>>>>> > >>>>>>>>> page_ext would introduce additional traversal cost. > >>>>>>>>> > >>>>>>>>> If the number of pages is substantial, this could incur signifi= cant > >>>>>>>>> overhead. What are your thoughts on this? I look forward to you= r > >>>>>>>>> suggestions. > >>>>>>>> My thinking is that these early allocations comprise a small por= tion > >>>>>>>> of overall memory consumed by the system. So, instead of trying = to > >>>>>>>> record and handle them in some alternative way, we just accept t= hat > >>>>>>>> some counters might not be exactly accurate and ignore those ear= ly > >>>>>>>> allocations. See how the early slab allocations are marked with = the > >>>>>>>> CODETAG_FLAG_INACCURATE flag and later reported as inaccurate. I= think > >>>>>>>> that's an acceptable alternative to introducing extra complexity= and > >>>>>>>> performance overhead. IOW, the benefits of accounting for these = early > >>>>>>>> allocations are low compared to the effort required to account f= or > >>>>>>>> them. Unless you found a simple and performant way to do that... > >>>>>>> I have been exploring possible solutions to this issue over the p= ast few > >>>>>>> days, > >>>>>>> > >>>>>>> but so far I have not come up with a good approach. > >>>>>>> > >>>>>>> I have counted the number of memory allocations that occur earlie= r than the > >>>>>>> > >>>>>>> allocation and initialization of our page_ext, and found that the= re are > >>>>>>> actually > >>>>>>> > >>>>>>> quite a lot of them. > >>>>>> Interesting... I wonder it's because deferred_struct_pages defers > >>>>>> page_ext initialization. Can you check if setting early_page_ext > >>>>>> reduces or eliminates these allocations before page_ext init cases= ? > >>>>> Yes, you are correct. In my 8-core 16GB virtual machine, I used a g= lobal > >>>>> counter > >>>>> > >>>>> to record these allocations. With early_page_ext enabled, there wer= e 130 > >>>>> allocations > >>>>> > >>>>> before page_ext initialization. Without early_page_ext, there were = 802 > >>>>> allocations > >>>>> > >>>>> before page_ext initialization. > >>>>> > >>>>> > >>>>>>> Similarly, I have made the following changes and collected the > >>>>>>> corresponding logs. > >>>>>>> > >>>>>>> diff --git a/mm/page_alloc.c b/mm/page_alloc.c > >>>>>>> index 2d4b6f1a554e..6db65b3d52d3 100644 > >>>>>>> --- a/mm/page_alloc.c > >>>>>>> +++ b/mm/page_alloc.c > >>>>>>> @@ -1293,6 +1293,8 @@ void __pgalloc_tag_add(struct page *page, s= truct > >>>>>>> task_struct *task, > >>>>>>> alloc_tag_add(&ref, task->alloc_tag, PAGE_SIZ= E * nr); > >>>>>>> update_page_tag_ref(handle, &ref); > >>>>>>> put_page_tag_ref(handle); > >>>>>>> + } else{ > >>>>>>> + pr_warn("__pgalloc_tag_add: get_page_tag_ref fail= ed! > >>>>>>> page=3D%p pfn=3D%lu nr=3D%u\n", page, page_to_pfn(page), nr); > >>>>>>> } > >>>>>>> } > >>>>>>> > >>>>>>> @@ -1314,6 +1316,8 @@ void __pgalloc_tag_sub(struct page *page, u= nsigned > >>>>>>> int nr) > >>>>>>> alloc_tag_sub(&ref, PAGE_SIZE * nr); > >>>>>>> update_page_tag_ref(handle, &ref); > >>>>>>> put_page_tag_ref(handle); > >>>>>>> + } else{ > >>>>>>> + pr_warn("__pgalloc_tag_sub: get_page_tag_ref fai= led! > >>>>>>> page=3D%p pfn=3D%lu nr=3D%u\n", page, page_to_pfn(page), nr); > >>>>>>> } > >>>>>>> } > >>>>>>> > >>>>>>> [ 0.261699] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001000 pfn=3D1048640 nr=3D2 > >>>>>>> [ 0.261711] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001100 pfn=3D1048644 nr=3D4 > >>>>>>> [ 0.261717] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001200 pfn=3D1048648 nr=3D4 > >>>>>>> [ 0.261721] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001300 pfn=3D1048652 nr=3D4 > >>>>>>> [ 0.261893] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001080 pfn=3D1048642 nr=3D2 > >>>>>>> [ 0.261917] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001400 pfn=3D1048656 nr=3D4 > >>>>>>> [ 0.262018] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001500 pfn=3D1048660 nr=3D2 > >>>>>>> [ 0.262024] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001600 pfn=3D1048664 nr=3D8 > >>>>>>> [ 0.262040] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001580 pfn=3D1048662 nr=3D1 > >>>>>>> [ 0.262048] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040015c0 pfn=3D1048663 nr=3D1 > >>>>>>> [ 0.262056] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001800 pfn=3D1048672 nr=3D2 > >>>>>>> [ 0.262064] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001880 pfn=3D1048674 nr=3D2 > >>>>>>> [ 0.262078] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001900 pfn=3D1048676 nr=3D2 > >>>>>>> [ 0.262196] SLUB: HWalign=3D64, Order=3D0-3, MinObjects=3D0, C= PUs=3D8, Nodes=3D1 > >>>>>>> [ 0.262213] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001980 pfn=3D1048678 nr=3D2 > >>>>>>> [ 0.262220] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001a00 pfn=3D1048680 nr=3D4 > >>>>>>> [ 0.262246] ODEBUG: selftest passed > >>>>>>> [ 0.262268] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001b00 pfn=3D1048684 nr=3D1 > >>>>>>> [ 0.262318] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001b40 pfn=3D1048685 nr=3D1 > >>>>>>> [ 0.262368] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001b80 pfn=3D1048686 nr=3D1 > >>>>>>> [ 0.262418] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001bc0 pfn=3D1048687 nr=3D1 > >>>>>>> [ 0.262469] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001c00 pfn=3D1048688 nr=3D1 > >>>>>>> [ 0.262519] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001c40 pfn=3D1048689 nr=3D1 > >>>>>>> [ 0.262569] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001c80 pfn=3D1048690 nr=3D1 > >>>>>>> [ 0.262620] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001cc0 pfn=3D1048691 nr=3D1 > >>>>>>> [ 0.262670] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001d00 pfn=3D1048692 nr=3D1 > >>>>>>> [ 0.262721] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001d40 pfn=3D1048693 nr=3D1 > >>>>>>> [ 0.262771] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001d80 pfn=3D1048694 nr=3D1 > >>>>>>> [ 0.262821] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001dc0 pfn=3D1048695 nr=3D1 > >>>>>>> [ 0.262871] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001e00 pfn=3D1048696 nr=3D1 > >>>>>>> [ 0.262923] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001e40 pfn=3D1048697 nr=3D1 > >>>>>>> [ 0.262974] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001e80 pfn=3D1048698 nr=3D1 > >>>>>>> [ 0.263024] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001ec0 pfn=3D1048699 nr=3D1 > >>>>>>> [ 0.263074] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001f00 pfn=3D1048700 nr=3D1 > >>>>>>> [ 0.263124] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001f40 pfn=3D1048701 nr=3D1 > >>>>>>> [ 0.263174] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001f80 pfn=3D1048702 nr=3D1 > >>>>>>> [ 0.263224] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004001fc0 pfn=3D1048703 nr=3D1 > >>>>>>> [ 0.263275] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002000 pfn=3D1048704 nr=3D1 > >>>>>>> [ 0.263325] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002040 pfn=3D1048705 nr=3D1 > >>>>>>> [ 0.263375] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002080 pfn=3D1048706 nr=3D1 > >>>>>>> [ 0.263427] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002400 pfn=3D1048720 nr=3D16 > >>>>>>> [ 0.263437] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040020c0 pfn=3D1048707 nr=3D1 > >>>>>>> [ 0.263463] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002100 pfn=3D1048708 nr=3D1 > >>>>>>> [ 0.263465] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002140 pfn=3D1048709 nr=3D1 > >>>>>>> [ 0.263467] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002180 pfn=3D1048710 nr=3D1 > >>>>>>> [ 0.263509] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002200 pfn=3D1048712 nr=3D4 > >>>>>>> [ 0.263512] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002800 pfn=3D1048736 nr=3D8 > >>>>>>> [ 0.263524] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040021c0 pfn=3D1048711 nr=3D1 > >>>>>>> [ 0.263536] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002300 pfn=3D1048716 nr=3D1 > >>>>>>> [ 0.263537] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002340 pfn=3D1048717 nr=3D1 > >>>>>>> [ 0.263539] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002380 pfn=3D1048718 nr=3D1 > >>>>>>> [ 0.263604] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004004000 pfn=3D1048832 nr=3D128 > >>>>>>> [ 0.263638] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004003000 pfn=3D1048768 nr=3D64 > >>>>>>> [ 0.263650] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002c00 pfn=3D1048752 nr=3D16 > >>>>>>> [ 0.263655] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040023c0 pfn=3D1048719 nr=3D1 > >>>>>>> [ 0.270582] __pgalloc_tag_sub: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040023c0 pfn=3D1048719 nr=3D1 > >>>>>>> [ 0.270591] ftrace: allocating 52717 entries in 208 pages > >>>>>>> [ 0.270592] ftrace: allocated 208 pages with 3 groups > >>>>>>> [ 0.270620] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004002a00 pfn=3D1048744 nr=3D8 > >>>>>>> [ 0.270636] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040023c0 pfn=3D1048719 nr=3D1 > >>>>>>> [ 0.270643] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006000 pfn=3D1048960 nr=3D1 > >>>>>>> [ 0.270649] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006040 pfn=3D1048961 nr=3D1 > >>>>>>> [ 0.270658] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004007000 pfn=3D1049024 nr=3D64 > >>>>>>> [ 0.270659] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006080 pfn=3D1048962 nr=3D2 > >>>>>>> [ 0.270722] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006100 pfn=3D1048964 nr=3D1 > >>>>>>> [ 0.270730] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006140 pfn=3D1048965 nr=3D1 > >>>>>>> [ 0.270738] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006180 pfn=3D1048966 nr=3D1 > >>>>>>> [ 0.270777] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040061c0 pfn=3D1048967 nr=3D1 > >>>>>>> [ 0.270786] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006200 pfn=3D1048968 nr=3D1 > >>>>>>> [ 0.270792] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006240 pfn=3D1048969 nr=3D1 > >>>>>>> [ 0.270833] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006300 pfn=3D1048972 nr=3D4 > >>>>>>> [ 0.270891] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006280 pfn=3D1048970 nr=3D1 > >>>>>>> [ 0.270980] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040062c0 pfn=3D1048971 nr=3D1 > >>>>>>> [ 0.271071] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006400 pfn=3D1048976 nr=3D1 > >>>>>>> [ 0.271156] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006440 pfn=3D1048977 nr=3D1 > >>>>>>> [ 0.271185] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006480 pfn=3D1048978 nr=3D2 > >>>>>>> [ 0.271301] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006500 pfn=3D1048980 nr=3D1 > >>>>>>> [ 0.271655] Dynamic Preempt: lazy > >>>>>>> [ 0.271662] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006580 pfn=3D1048982 nr=3D2 > >>>>>>> [ 0.271752] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006600 pfn=3D1048984 nr=3D4 > >>>>>>> [ 0.271762] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004010000 pfn=3D1049600 nr=3D4 > >>>>>>> [ 0.271824] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006540 pfn=3D1048981 nr=3D1 > >>>>>>> [ 0.271916] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006700 pfn=3D1048988 nr=3D2 > >>>>>>> [ 0.271964] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006780 pfn=3D1048990 nr=3D1 > >>>>>>> [ 0.272099] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea00040067c0 pfn=3D1048991 nr=3D1 > >>>>>>> [ 0.272138] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006800 pfn=3D1048992 nr=3D2 > >>>>>>> [ 0.272144] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006a00 pfn=3D1049000 nr=3D8 > >>>>>>> [ 0.272249] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006c00 pfn=3D1049008 nr=3D8 > >>>>>>> [ 0.272319] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006880 pfn=3D1048994 nr=3D2 > >>>>>>> [ 0.272351] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006900 pfn=3D1048996 nr=3D4 > >>>>>>> [ 0.272424] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004006e00 pfn=3D1049016 nr=3D8 > >>>>>>> [ 0.272485] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008000 pfn=3D1049088 nr=3D8 > >>>>>>> [ 0.272535] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008200 pfn=3D1049096 nr=3D2 > >>>>>>> [ 0.272600] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008400 pfn=3D1049104 nr=3D8 > >>>>>>> [ 0.272663] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008300 pfn=3D1049100 nr=3D4 > >>>>>>> [ 0.272694] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008280 pfn=3D1049098 nr=3D2 > >>>>>>> [ 0.272708] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008600 pfn=3D1049112 nr=3D8 > >>>>>>> > >>>>>>> [ 0.272924] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008880 pfn=3D1049122 nr=3D2 > >>>>>>> [ 0.272934] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008900 pfn=3D1049124 nr=3D2 > >>>>>>> [ 0.272952] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008c00 pfn=3D1049136 nr=3D4 > >>>>>>> [ 0.273035] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008980 pfn=3D1049126 nr=3D2 > >>>>>>> [ 0.273062] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008e00 pfn=3D1049144 nr=3D8 > >>>>>>> [ 0.273674] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008d00 pfn=3D1049140 nr=3D1 > >>>>>>> [ 0.273884] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008d80 pfn=3D1049142 nr=3D2 > >>>>>>> [ 0.273943] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009000 pfn=3D1049152 nr=3D2 > >>>>>>> [ 0.274379] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009080 pfn=3D1049154 nr=3D2 > >>>>>>> [ 0.274575] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009200 pfn=3D1049160 nr=3D8 > >>>>>>> [ 0.274617] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009100 pfn=3D1049156 nr=3D4 > >>>>>>> [ 0.274794] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009400 pfn=3D1049168 nr=3D2 > >>>>>>> [ 0.274840] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009480 pfn=3D1049170 nr=3D2 > >>>>>>> [ 0.275057] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009500 pfn=3D1049172 nr=3D2 > >>>>>>> [ 0.275092] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009580 pfn=3D1049174 nr=3D2 > >>>>>>> [ 0.275134] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009600 pfn=3D1049176 nr=3D8 > >>>>>>> [ 0.275211] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009800 pfn=3D1049184 nr=3D4 > >>>>>>> [ 0.275510] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009900 pfn=3D1049188 nr=3D2 > >>>>>>> [ 0.275548] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009980 pfn=3D1049190 nr=3D2 > >>>>>>> [ 0.275976] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009a00 pfn=3D1049192 nr=3D8 > >>>>>>> [ 0.275987] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009c00 pfn=3D1049200 nr=3D2 > >>>>>>> [ 0.276139] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009c80 pfn=3D1049202 nr=3D2 > >>>>>>> [ 0.276152] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004008d40 pfn=3D1049141 nr=3D1 > >>>>>>> [ 0.276242] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009d00 pfn=3D1049204 nr=3D1 > >>>>>>> [ 0.276358] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009d40 pfn=3D1049205 nr=3D1 > >>>>>>> [ 0.276444] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009d80 pfn=3D1049206 nr=3D1 > >>>>>>> [ 0.276526] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009dc0 pfn=3D1049207 nr=3D1 > >>>>>>> [ 0.276615] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009e00 pfn=3D1049208 nr=3D1 > >>>>>>> [ 0.276696] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009e40 pfn=3D1049209 nr=3D1 > >>>>>>> [ 0.276792] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009e80 pfn=3D1049210 nr=3D1 > >>>>>>> [ 0.276827] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009f00 pfn=3D1049212 nr=3D2 > >>>>>>> [ 0.276891] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009ec0 pfn=3D1049211 nr=3D1 > >>>>>>> [ 0.276999] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009f80 pfn=3D1049214 nr=3D1 > >>>>>>> [ 0.277082] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea0004009fc0 pfn=3D1049215 nr=3D1 > >>>>>>> [ 0.277172] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea000400a000 pfn=3D1049216 nr=3D1 > >>>>>>> [ 0.277257] __pgalloc_tag_add: get_page_tag_ref failed! > >>>>>>> page=3Dffffea000400a040 pfn=3D1049217 nr=3D1 > >>>>>>> > >>>>>>> and so on. > >>>>>>> > >>>>>>> > >>>>>>>> I think your earlier patch can effectively detect these early > >>>>>>>> allocations and suppress the warnings. We should also mark these > >>>>>>>> allocations with CODETAG_FLAG_INACCURATE. > >>>>>>> Thanks to an excellent AI review, I realized there are issues wit= h > >>>>>>> > >>>>>>> my original patch. One problem is the 256-element array; another > >>>>>> Yes, if there are lots of such allocations, it's not appropriate. > >>>>>> > >>>>>>> is that it involves allocation and free operations =E2=80=94 mean= ing we need > >>>>>>> > >>>>>>> to record entries at __pgalloc_tag_add and remove them at __pgall= oc_tag_sub, > >>>>>>> > >>>>>>> which introduces a noticeable overhead. I'm wondering if we can i= nstead > >>>>>>> set a flag > >>>>>>> > >>>>>>> bit in page flags during the early boot stage, which I'll refer t= o as > >>>>>>> EARLY_ALLOC_FLAGS. > >>>>>>> > >>>>>>> Then, in __pgalloc_tag_sub, we first check for EARLY_ALLOC_FLAGS.= If > >>>>>>> set, we clear the > >>>>>>> > >>>>>>> flag and return immediately; otherwise, we perform the actual > >>>>>>> subtraction of the tag count. > >>>>>>> > >>>>>>> This approach seems somewhat similar to the idea behind > >>>>>>> mem_profiling_compressed. > >>>>>> That seems doable but let's first check if we can make page_ext > >>>>>> initialization happen before these allocations. That would be the > >>>>>> ideal path. If it's not possible then we can focus on alternatives > >>>>>> like the one you propose. > >>>>> Yes, the ideal scenario would be to have page_ext initialization > >>>>> complete before > >>>>> > >>>>> these allocations occur. I just did a code walkthrough and found th= at > >>>>> this resembles > >>>>> > >>>>> the FLATMEM implementation approach - FLATMEM allocates page_ext be= fore > >>>>> the buddy > >>>>> > >>>>> system initialization, so it doesn't seem to encounter the issue we= 're > >>>>> facing now. > >>>>> > >>>>> https://elixir.bootlin.com/linux/v7.0-rc5/source/mm/mm_init.c#L2707 > >>>> Yes, page_ext_init_flatmem() looks like an interesting option and it > >>>> would not work with sparsemem. TBH I would prefer to find a simple > >>>> solution that can identify early init allocations, mark them inaccua= te > >>>> and suppress the warning rather than introduce some complex mechanis= m > >>>> to account for them which would work only is some cases (flatmem). > >>>> With your original approach I think the only real issue is the size = of > >>>> the array that might be too small. The other issue you mentioned abo= ut > >>>> allocated page being freed and then re-allocated after page_ext is > >>>> inialized but before clear_page_tag_ref() is called is not really a > >>>> problem. Yes, we will lose that counter's value but it's similar to > >>>> other early allocations which we just treat as inaccurate. We can al= so > >>>> minimize the possibility of this happening by moving > >>>> clear_page_tag_ref() into init_page_alloc_tagging(). > >>>> > >>>> I don't like the pageflag option you mentioned because it adds an > >>>> extra condition check into __pgalloc_tag_sub() which will be execute= d > >>>> even after the init stage is over. > >>>> I'll look into this some more tomorrow as it's quite late now. > >> > >> Hi Suren > >> > >> > >>> Just though of something. Are all these pages allocated by slab? If > >>> so, I think slab does not use page->lru (need to double-check) and we > >>> could add all these pages allocated during early init into a list and > >>> then set their page_ext reference to CODETAG_EMPTY in > >>> init_page_alloc_tagging(). > >> Got your point. > >> > >> > >> There will indeed be some non-SLAB memory allocations here, such as th= e > >> following: > >> > >> > >> CPU: 0 UID: 0 PID: 0 Comm: swapper/0 Not tainted > >> 7.0.0-rc4-00001-g6392c3a6119e-dirty #31 PREEMPT(lazy) > >> [ 0.326607] Hardware name: Red Hat KVM, BIOS > >> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > >> [ 0.326608] Call Trace: > >> [ 0.326608] > >> [ 0.326609] dump_stack_lvl+0x53/0x70 > >> [ 0.326611] __pgalloc_tag_add+0x407/0x700 > >> [ 0.326616] get_page_from_freelist+0xa54/0x1310 > >> [ 0.326618] __alloc_frozen_pages_noprof+0x206/0x4c0 > >> [ 0.326623] alloc_pages_mpol+0x13a/0x3f0 > >> [ 0.326627] alloc_pages_noprof+0xf6/0x2b0 > >> [ 0.326628] __pmd_alloc+0x743/0x9c0 > >> [ 0.326630] vmap_range_noflush+0xac0/0x10a0 > >> [ 0.326637] ioremap_page_range+0x17c/0x250 > >> [ 0.326639] __ioremap_caller+0x437/0x5c0 > >> [ 0.326645] acpi_os_map_iomem+0x4c0/0x660 > >> [ 0.326647] acpi_tb_verify_temp_table+0x1c0/0x580 > >> [ 0.326649] acpi_reallocate_root_table+0x2ad/0x460 > >> [ 0.326655] acpi_early_init+0x111/0x460 > >> [ 0.326657] start_kernel+0x271/0x3c0 > >> [ 0.326659] x86_64_start_reservations+0x18/0x30 > >> [ 0.326660] x86_64_start_kernel+0xe2/0xf0 > >> [ 0.326662] common_startup_64+0x13e/0x141 > >> [ 0.326663] > >> > >> CPU: 0 UID: 0 PID: 2 Comm: kthreadd Not tainted > >> 7.0.0-rc4-00001-g6392c3a6119e-dirty #31 PREEMPT(lazy) > >> [ 0.329167] Hardware name: Red Hat KVM, BIOS > >> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > >> [ 0.329167] Call Trace: > >> [ 0.329167] > >> [ 0.329167] dump_stack_lvl+0x53/0x70 > >> [ 0.329167] __pgalloc_tag_add+0x407/0x700 > >> [ 0.329167] get_page_from_freelist+0xa54/0x1310 > >> [ 0.329167] __alloc_frozen_pages_noprof+0x206/0x4c0 > >> [ 0.329167] __alloc_pages_noprof+0x10/0x1b0 > >> [ 0.329167] dup_task_struct+0x163/0x8c0 > >> [ 0.329167] copy_process+0x390/0x4a70 > >> [ 0.329167] kernel_clone+0xe1/0x830 > >> [ 0.329167] kernel_thread+0xcb/0x110 > >> [ 0.329167] kthreadd+0x8a2/0xc60 > >> [ 0.329167] ret_from_fork+0x551/0x720 > >> [ 0.329167] ret_from_fork_asm+0x1a/0x30 > >> [ 0.329167] > >> > >> CPU: 0 UID: 0 PID: 2 Comm: kthreadd Not tainted > >> 7.0.0-rc4-00001-g6392c3a6119e-dirty #31 PREEMPT(lazy) > >> [ 0.329167] Hardware name: Red Hat KVM, BIOS > >> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > >> [ 0.329167] Call Trace: > >> [ 0.329167] > >> [ 0.329167] dump_stack_lvl+0x53/0x70 > >> [ 0.329167] __pgalloc_tag_add+0x407/0x700 > >> [ 0.329167] get_page_from_freelist+0xa54/0x1310 > >> [ 0.329167] __alloc_frozen_pages_noprof+0x206/0x4c0 > >> [ 0.329167] __alloc_pages_noprof+0x10/0x1b0 > >> [ 0.329167] dup_task_struct+0x163/0x8c0 > >> [ 0.329167] copy_process+0x390/0x4a70 > >> [ 0.329167] kernel_clone+0xe1/0x830 > >> [ 0.329167] kernel_thread+0xcb/0x110 > >> [ 0.329167] kthreadd+0x8a2/0xc60 > >> [ 0.329167] ret_from_fork+0x551/0x720 > >> [ 0.329167] ret_from_fork_asm+0x1a/0x30 > >> [ 0.329167] > >> > >> CPU: 4 UID: 0 PID: 1 Comm: swapper/0 Not tainted > >> 7.0.0-rc4-00001-g6392c3a6119e-dirty #31 PREEMPT(lazy) > >> [ 0.434265] Hardware name: Red Hat KVM, BIOS > >> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > >> [ 0.434266] Call Trace: > >> [ 0.434266] > >> [ 0.434266] dump_stack_lvl+0x53/0x70 > >> [ 0.434268] __pgalloc_tag_add+0x407/0x700 > >> [ 0.434272] get_page_from_freelist+0xa54/0x1310 > >> [ 0.434274] __alloc_frozen_pages_noprof+0x206/0x4c0 > >> [ 0.434279] alloc_pages_exact_nid_noprof+0x10f/0x380 > >> [ 0.434283] init_section_page_ext+0x167/0x370 > >> [ 0.434284] page_ext_init+0x451/0x620 > >> [ 0.434287] page_alloc_init_late+0x553/0x630 > >> [ 0.434290] kernel_init_freeable+0x7be/0xd30 > >> [ 0.434294] kernel_init+0x1f/0x1f0 > >> [ 0.434295] ret_from_fork+0x551/0x720 > >> [ 0.434301] ret_from_fork_asm+0x1a/0x30 > >> [ 0.434303] > >> > >> CPU: 0 UID: 0 PID: 1 Comm: swapper/0 Not tainted > >> 7.0.0-rc4-00001-g6392c3a6119e-dirty #31 PREEMPT(lazy) > >> [ 0.346712] Hardware name: Red Hat KVM, BIOS > >> rel-1.16.3-0-ga6ed6b701f0a-prebuilt.qemu.org 04/01/2014 > >> [ 0.346713] Call Trace: > >> [ 0.346713] > >> [ 0.346714] dump_stack_lvl+0x53/0x70 > >> [ 0.346715] __pgalloc_tag_add+0x407/0x700 > >> [ 0.346720] get_page_from_freelist+0xa54/0x1310 > >> [ 0.346723] __alloc_frozen_pages_noprof+0x206/0x4c0 > >> [ 0.346729] __alloc_pages_noprof+0x10/0x1b0 > >> [ 0.346731] alloc_cpu_data+0x96/0x210 > >> [ 0.346732] rb_allocate_cpu_buffer+0xb93/0x1500 > >> [ 0.346739] trace_rb_cpu_prepare+0x21a/0x4f0 > >> [ 0.346753] cpuhp_invoke_callback+0x6db/0x14b0 > >> [ 0.346755] __cpuhp_invoke_callback_range+0xde/0x1d0 > >> [ 0.346759] _cpu_up+0x395/0x880 > >> [ 0.346761] cpu_up+0x1bb/0x210 > >> [ 0.346762] cpuhp_bringup_mask+0xd2/0x150 > >> [ 0.346763] bringup_nonboot_cpus+0x12b/0x170 > >> [ 0.346764] smp_init+0x2f/0x100 > >> [ 0.346766] kernel_init_freeable+0x7a5/0xd30 > >> [ 0.346769] kernel_init+0x1f/0x1f0 > >> [ 0.346771] ret_from_fork+0x551/0x720 > >> [ 0.346776] ret_from_fork_asm+0x1a/0x30 > >> [ 0.346778] > >> > >> and so on... > >> > >> > >> In fact, I previously conducted extensive and prolonged stress testing > >> > >> on memory profiling. After our efforts to address several WARN cases, > >> > >> one remaining scenario we are addressing is the warning triggered duri= ng > >> > >> early slab cache reclaim =E2=80=94 which is precisely the situation we= are currently > >> > >> encountering (although I cannot guarantee that all edge cases have bee= n > >> > >> covered by our stress testing). During the stress testing process, thi= s > >> warning > >> > >> did indeed manifest. However, the current environment triggers KASAN s= lab > >> > >> cache reclaim earlier than anticipated. > >> > >> > >> Although the memory allocated prior to page_ext initialization has a > >> relatively low probability of > >> > >> being released in subsequent operations (at least we have not > >> encountered such cases up to now), > >> > >> I remain uncertain whether there are any overlooked edge cases when > >> considering only slab-backed pages. > > Hi Suren > > > > Ok, I guess specialized solution for slab would not work then. I want > > to check on my side and understand how the number of these early > > allocation scales. Is it higher for bigger machines or stays constant. > > If the latter I think your original simple solution with some fixups > > can still work. I'll need to instrument my code to capture these early > > allocations and see where they originate. If you have a patch already > > doing that it would help speed it up for me. > > Thanks, > > Suren. > > OK, my V2 patch is as follows: Thanks! I'll go over it but first I need to check if the number of early allocations is constant or dependent on some factors like machine size (as I mentioned before). I hope to carve out some time to investigate that this Friday. We should also probably start a separate thread for this v2 as this email thread is getting painfully long. > > > diff --git a/include/linux/alloc_tag.h b/include/linux/alloc_tag.h > index d40ac39bfbe8..bf226c2be2ad 100644 > --- a/include/linux/alloc_tag.h > +++ b/include/linux/alloc_tag.h > @@ -74,6 +74,8 @@ static inline void set_codetag_empty(union codetag_ref > *ref) > > #ifdef CONFIG_MEM_ALLOC_PROFILING > > +void alloc_tag_add_early_pfn(unsigned long pfn); > + > #define ALLOC_TAG_SECTION_NAME "alloc_tags" > > struct codetag_bytes { > diff --git a/include/linux/pgalloc_tag.h b/include/linux/pgalloc_tag.h > index 38a82d65e58e..951d33362268 100644 > --- a/include/linux/pgalloc_tag.h > +++ b/include/linux/pgalloc_tag.h > @@ -181,7 +181,7 @@ static inline struct alloc_tag > *__pgalloc_tag_get(struct page *page) > > if (get_page_tag_ref(page, &ref, &handle)) { > alloc_tag_sub_check(&ref); > - if (ref.ct) > + if (ref.ct && !is_codetag_empty(&ref)) > tag =3D ct_to_alloc_tag(ref.ct); > put_page_tag_ref(handle); > } > diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c > index 58991ab09d84..55c134a71cd0 100644 > --- a/lib/alloc_tag.c > +++ b/lib/alloc_tag.c > @@ -6,6 +6,7 @@ > #include > #include > #include > +#include > #include > #include > #include > @@ -26,6 +27,85 @@ static bool mem_profiling_support; > > static struct codetag_type *alloc_tag_cttype; > > +#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG > + > +/* > + * page_ext is allocated and initialized relatively late during boot. > + * Some pages are allocated before page_ext becomes available. > + * Track these early PFNs and clear their codetag refs later to avoid > + * warnings when they are freed. > + */ > + > +#define EARLY_ALLOC_PFN_MAX 256 > + > +static unsigned long early_pfns[EARLY_ALLOC_PFN_MAX] __initdata; > +static atomic_t early_pfn_count __initdata =3D ATOMIC_INIT(0); > + > +static void __init __alloc_tag_add_early_pfn(unsigned long pfn) > +{ > + int old_idx, new_idx; > + > + do { > + old_idx =3D atomic_read(&early_pfn_count); > + if (old_idx >=3D EARLY_ALLOC_PFN_MAX) > + return; > + new_idx =3D old_idx + 1; > + } while (!atomic_try_cmpxchg(&early_pfn_count, &old_idx, new_idx)); > + > + early_pfns[old_idx] =3D pfn; > +} > + > +static void (*alloc_tag_add_early_pfn_ptr)(unsigned long pfn) __refdata = =3D > + __alloc_tag_add_early_pfn; > + > +void alloc_tag_add_early_pfn(unsigned long pfn) > +{ > + if (static_key_enabled(&mem_profiling_compressed)) > + return; > + > + if (alloc_tag_add_early_pfn_ptr) > + alloc_tag_add_early_pfn_ptr(pfn); > +} > + > +static void __init clear_early_alloc_pfn_tag_refs(void) > +{ > + unsigned int i; > + > + for (i =3D 0; i < atomic_read(&early_pfn_count); i++) { > + unsigned long pfn =3D early_pfns[i]; > + > + if (pfn_valid(pfn)) { > + struct page *page =3D pfn_to_page(pfn); > + union pgtag_ref_handle handle; > + union codetag_ref ref; > + > + if (get_page_tag_ref(page, &ref, &handle)) { > + /* > + * An early-allocated page could be freed and reallocate= d > + * after its page_ext is initialized but before we > clear it. > + * In that case, it already has a valid tag set. > + * We should not overwrite that valid tag with > CODETAG_EMPTY. > + */ > + if (ref.ct) { > + put_page_tag_ref(handle); > + continue; > + } > + > + set_codetag_empty(&ref); > + update_page_tag_ref(handle, &ref); > + put_page_tag_ref(handle); > + } > + } > + > + atomic_set(&early_pfn_count, 0); > + > + alloc_tag_add_early_pfn_ptr =3D NULL; > +} > +#else /* !CONFIG_MEM_ALLOC_PROFILING_DEBUG */ > +inline void alloc_tag_add_early_pfn(unsigned long pfn) {} > +static inline void __init clear_early_alloc_pfn_tag_refs(void) {} > +#endif > + > #ifdef CONFIG_ARCH_MODULE_NEEDS_WEAK_PER_CPU > DEFINE_PER_CPU(struct alloc_tag_counters, _shared_alloc_tag); > EXPORT_SYMBOL(_shared_alloc_tag); > @@ -760,6 +840,7 @@ static __init bool need_page_alloc_tagging(void) > > static __init void init_page_alloc_tagging(void) > { > + clear_early_alloc_pfn_tag_refs(); > } > > struct page_ext_operations page_alloc_tagging_ops =3D { > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 2d4b6f1a554e..5ce5c4ba401f 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -1293,6 +1293,12 @@ void __pgalloc_tag_add(struct page *page, struct > task_struct *task, > alloc_tag_add(&ref, task->alloc_tag, PAGE_SIZE * nr); > update_page_tag_ref(handle, &ref); > put_page_tag_ref(handle); > + } else { > + /* > + * page_ext is not available yet, record the pfn so we can > + * clear the tag ref later when page_ext is initialized. > + */ > + alloc_tag_add_early_pfn(page_to_pfn(page)); > } > } > > Although this 256-entry array remains unmodified for now, I will locally > record the occurrence counts > > of these various early memory allocations. Hopefully this will be > helpful to you. > > > Thanks > > Hao > > > > >> > >> Thanks > >> Hao > >> > >>>> Thanks, > >>>> Suren. > >>>> > >>>>> However, I'm not entirely certain whether SPARSEMEM can guarantee t= he > >>>>> same behavior. > >>>>> > >>>>> > >>>>>>> I would appreciate your valuable feedback and any better suggesti= ons you > >>>>>>> might have. > >>>>>> Thanks for pursuing this! I'll help in any way I can. > >>>>>> Suren. > >>>>> Thank you so much for your patient guidance and assistance. > >>>>> > >>>>> I truly appreciate your willingness to share your knowledge and ins= ights. > >>>>> > >>>>> Thanks, > >>>>> Hao > >>>>> > >>>>>>> Thanks > >>>>>>> > >>>>>>> Hao > >>>>>>> > >>>>>>>> Thanks, > >>>>>>>> Suren. > >>>>>>>> > >>>>>>>>> Thanks > >>>>>>>>> > >>>>>>>>> Hao > >>>>>>>>> > >>>>>>>>>>> Thanks. > >>>>>>>>>>> > >>>>>>>>>>> > >>>>>>>>>>>>>>> If the slab cache has no free objects, it falls back > >>>>>>>>>>>>>>> to the buddy allocator to allocate memory. However, at th= is point page_ext > >>>>>>>>>>>>>>> is not yet fully initialized, so these newly allocated pa= ges have no > >>>>>>>>>>>>>>> codetag set. These pages may later be reclaimed by KASAN,= which causes > >>>>>>>>>>>>>>> the warning to trigger when they are freed because their = codetag ref is > >>>>>>>>>>>>>>> still empty. > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> Use a global array to track pages allocated before page_e= xt is fully > >>>>>>>>>>>>>>> initialized, similar to how kmemleak tracks early allocat= ions. > >>>>>>>>>>>>>>> When page_ext initialization completes, set their codetag > >>>>>>>>>>>>>>> to empty to avoid warnings when they are freed later. > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> ... > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> --- a/include/linux/alloc_tag.h > >>>>>>>>>>>>>>> +++ b/include/linux/alloc_tag.h > >>>>>>>>>>>>>>> @@ -74,6 +74,9 @@ static inline void set_codetag_empty(un= ion codetag_ref *ref) > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> #ifdef CONFIG_MEM_ALLOC_PROFILING > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> +bool mem_profiling_is_available(void); > >>>>>>>>>>>>>>> +void alloc_tag_add_early_pfn(unsigned long pfn); > >>>>>>>>>>>>>>> + > >>>>>>>>>>>>>>> #define ALLOC_TAG_SECTION_NAME "alloc_tags" > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> struct codetag_bytes { > >>>>>>>>>>>>>>> diff --git a/lib/alloc_tag.c b/lib/alloc_tag.c > >>>>>>>>>>>>>>> index 58991ab09d84..a5bf4e72c154 100644 > >>>>>>>>>>>>>>> --- a/lib/alloc_tag.c > >>>>>>>>>>>>>>> +++ b/lib/alloc_tag.c > >>>>>>>>>>>>>>> @@ -6,6 +6,7 @@ > >>>>>>>>>>>>>>> #include > >>>>>>>>>>>>>>> #include > >>>>>>>>>>>>>>> #include > >>>>>>>>>>>>>>> +#include > >>>>>>>>>>>>>>> #include > >>>>>>>>>>>>>>> #include > >>>>>>>>>>>>>>> #include > >>>>>>>>>>>>>>> @@ -26,6 +27,82 @@ static bool mem_profiling_support; > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> static struct codetag_type *alloc_tag_cttype; > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> +/* > >>>>>>>>>>>>>>> + * State of the alloc_tag > >>>>>>>>>>>>>>> + * > >>>>>>>>>>>>>>> + * This is used to describe the states of the alloc_tag = during bootup. > >>>>>>>>>>>>>>> + * > >>>>>>>>>>>>>>> + * When we need to allocate page_ext to store codetag, w= e face an > >>>>>>>>>>>>>>> + * initialization timing problem: > >>>>>>>>>>>>>>> + * > >>>>>>>>>>>>>>> + * Due to initialization order, pages may be allocated v= ia buddy system > >>>>>>>>>>>>>>> + * before page_ext is fully allocated and initialized. A= lthough these > >>>>>>>>>>>>>>> + * pages call the allocation hooks, the codetag will not= be set because > >>>>>>>>>>>>>>> + * page_ext is not yet available. > >>>>>>>>>>>>>>> + * > >>>>>>>>>>>>>>> + * When these pages are later free to the buddy system, = it triggers > >>>>>>>>>>>>>>> + * warnings because their codetag is actually empty if > >>>>>>>>>>>>>>> + * CONFIG_MEM_ALLOC_PROFILING_DEBUG is enabled. > >>>>>>>>>>>>>>> + * > >>>>>>>>>>>>>>> + * Additionally, in this situation, we cannot record det= ailed allocation > >>>>>>>>>>>>>>> + * information for these pages. > >>>>>>>>>>>>>>> + */ > >>>>>>>>>>>>>>> +enum mem_profiling_state { > >>>>>>>>>>>>>>> + DOWN, /* No mem_profiling functio= nality yet */ > >>>>>>>>>>>>>>> + UP /* Everything is working */ > >>>>>>>>>>>>>>> +}; > >>>>>>>>>>>>>>> + > >>>>>>>>>>>>>>> +static enum mem_profiling_state mem_profiling_state =3D = DOWN; > >>>>>>>>>>>>>>> + > >>>>>>>>>>>>>>> +bool mem_profiling_is_available(void) > >>>>>>>>>>>>>>> +{ > >>>>>>>>>>>>>>> + return mem_profiling_state =3D=3D UP; > >>>>>>>>>>>>>>> +} > >>>>>>>>>>>>>>> + > >>>>>>>>>>>>>>> +#ifdef CONFIG_MEM_ALLOC_PROFILING_DEBUG > >>>>>>>>>>>>>>> + > >>>>>>>>>>>>>>> +#define EARLY_ALLOC_PFN_MAX 256 > >>>>>>>>>>>>>>> + > >>>>>>>>>>>>>>> +static unsigned long early_pfns[EARLY_ALLOC_PFN_MAX]; > >>>>>>>>>>>>>> It's unfortunate that this isn't __initdata. > >>>>>>>>>>>>>> > >>>>>>>>>>>>>>> +static unsigned int early_pfn_count; > >>>>>>>>>>>>>>> +static DEFINE_SPINLOCK(early_pfn_lock); > >>>>>>>>>>>>>>> + > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> ... > >>>>>>>>>>>>>>> > >>>>>>>>>>>>>>> --- a/mm/page_alloc.c > >>>>>>>>>>>>>>> +++ b/mm/page_alloc.c > >>>>>>>>>>>>>>> @@ -1293,6 +1293,13 @@ void __pgalloc_tag_add(struct page= *page, struct task_struct *task, > >>>>>>>>>>>>>>> alloc_tag_add(&ref, task->alloc_tag, = PAGE_SIZE * nr); > >>>>>>>>>>>>>>> update_page_tag_ref(handle, &ref); > >>>>>>>>>>>>>>> put_page_tag_ref(handle); > >>>>>>>>>>>>>>> + } else { > >>>>>>>>>>>>> This branch can be marked as "unlikely". > >>>>>>>>>>>>> > >>>>>>>>>>>>>>> + /* > >>>>>>>>>>>>>>> + * page_ext is not available yet, record th= e pfn so we can > >>>>>>>>>>>>>>> + * clear the tag ref later when page_ext is= initialized. > >>>>>>>>>>>>>>> + */ > >>>>>>>>>>>>>>> + if (!mem_profiling_is_available()) > >>>>>>>>>>>>>>> + alloc_tag_add_early_pfn(page_to_pfn= (page)); > >>>>>>>>>>>>>>> } > >>>>>>>>>>>>>>> } > >>>>>>>>>>>>>> All because of this, I believe. Is this fixable? > >>>>>>>>>>>>>> > >>>>>>>>>>>>>> If we take that `else', we know we're running in __init co= de, yes? I > >>>>>>>>>>>>>> don't see how `__init pgalloc_tag_add_early()' could be ma= de to work. > >>>>>>>>>>>>>> hrm. Something clever, please. > >>>>>>>>>>>>> We can have a pointer to a function that is initialized to = point to > >>>>>>>>>>>>> alloc_tag_add_early_pfn, which is defined as __init and use= s > >>>>>>>>>>>>> early_pfns which now can be defined as __initdata. After > >>>>>>>>>>>>> clear_early_alloc_pfn_tag_refs() is done we reset that poin= ter to > >>>>>>>>>>>>> NULL. __pgalloc_tag_add() instead of calling alloc_tag_add_= early_pfn() > >>>>>>>>>>>>> directly checks that pointer and if it's not NULL then call= s the > >>>>>>>>>>>>> function that it points to. This way __pgalloc_tag_add() wh= ich is not > >>>>>>>>>>>>> an __init function will be invoking alloc_tag_add_early_pfn= () __init > >>>>>>>>>>>>> function only until we are done with initialization. I have= n't tried > >>>>>>>>>>>>> this but I think that should work. This also eliminates the= need for > >>>>>>>>>>>>> mem_profiling_state variable since we can use this function= pointer > >>>>>>>>>>>>> instead. > >>>>>>>>>>>>> > >>>>>>>>>>>>>