From: David Hildenbrand <david@redhat.com>
To: Nico Pache <npache@redhat.com>, Ryan Roberts <ryan.roberts@arm.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
anshuman.khandual@arm.com, catalin.marinas@arm.com,
cl@gentwo.org, vbabka@suse.cz, mhocko@suse.com,
apopple@nvidia.com, dave.hansen@linux.intel.com, will@kernel.org,
baohua@kernel.org, jack@suse.cz, srivatsa@csail.mit.edu,
haowenchao22@gmail.com, hughd@google.com,
aneesh.kumar@kernel.org, yang@os.amperecomputing.com,
peterx@redhat.com, ioworker0@gmail.com,
wangkefeng.wang@huawei.com, ziy@nvidia.com, jglisse@google.com,
surenb@google.com, vishal.moola@gmail.com, zokeefe@google.com,
zhengqi.arch@bytedance.com, jhubbard@nvidia.com,
21cnbao@gmail.com, willy@infradead.org,
kirill.shutemov@linux.intel.com, aarcange@redhat.com,
raquini@redhat.com, dev.jain@arm.com, sunnanyong@huawei.com,
usamaarif642@gmail.com, audra@redhat.com,
akpm@linux-foundation.org
Subject: Re: [RFC 00/11] khugepaged: mTHP support
Date: Mon, 20 Jan 2025 13:54:13 +0100 [thread overview]
Message-ID: <37375ace-5601-4d6c-9dac-d1c8268698e9@redhat.com> (raw)
In-Reply-To: <CAA1CXcBejAuvUpqBKmY-VPy6TnVCWwDEwxqbyb08JTX5iBTENQ@mail.gmail.com>
>> I think the 1 problem that emerged during review of Dev's series, which we don't
>> have a proper solution to yet, is the issue of "creep", where regions can be
>> collapsed to progressively higher orders through iterative scans. At each
>> collapse, the required thresholds (e.g. max_ptes_none) are met, and the collapse
>> effectively adds more non-none ptes so the next scan will then collapse to even
>> higher order. Does your solution suffer from this (theoretical/edge case) issue?
>> If not, how did you solve?
>
> Yes sadly it suffers from the same issue. bringing max_ptes_none much
> lower as a default would "help".
Can we just keep it simple and only support max_ptes_none = 511
("pagefault behavior" -- PMD_NR_PAGES - 1) or max_ptes_none = 0
("deferred behavior") and document that the other weird configurations
will make mTHP skip, because "weird and unexpetced" ? :)
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2025-01-20 12:54 UTC|newest]
Thread overview: 54+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-08 23:31 [RFC 00/11] khugepaged: mTHP support Nico Pache
2025-01-08 23:31 ` [RFC 01/11] introduce khugepaged_collapse_single_pmd to collapse a single pmd Nico Pache
2025-01-10 6:25 ` Dev Jain
2025-01-08 23:31 ` [RFC 02/11] khugepaged: refactor madvise_collapse and khugepaged_scan_mm_slot Nico Pache
2025-01-08 23:31 ` [RFC 03/11] khugepaged: Don't allocate khugepaged mm_slot early Nico Pache
2025-01-10 6:11 ` Dev Jain
2025-01-10 19:37 ` Nico Pache
2025-01-08 23:31 ` [RFC 04/11] khugepaged: rename hpage_collapse_* to khugepaged_* Nico Pache
2025-01-08 23:31 ` [RFC 05/11] khugepaged: generalize hugepage_vma_revalidate for mTHP support Nico Pache
2025-01-08 23:31 ` [RFC 06/11] khugepaged: generalize alloc_charge_folio " Nico Pache
2025-01-10 6:23 ` Dev Jain
2025-01-10 19:41 ` Nico Pache
2025-01-08 23:31 ` [RFC 07/11] khugepaged: generalize __collapse_huge_page_* " Nico Pache
2025-01-10 6:38 ` Dev Jain
2025-01-08 23:31 ` [RFC 08/11] khugepaged: introduce khugepaged_scan_bitmap " Nico Pache
2025-01-10 3:46 ` kernel test robot
2025-01-10 9:05 ` Dev Jain
2025-01-10 21:48 ` Nico Pache
2025-01-12 11:23 ` Dev Jain
2025-01-13 22:25 ` Nico Pache
2025-01-10 14:54 ` Dev Jain
2025-01-10 21:48 ` Nico Pache
2025-01-12 15:13 ` Dev Jain
2025-01-12 16:41 ` Dev Jain
2025-01-08 23:31 ` [RFC 09/11] khugepaged: add " Nico Pache
2025-01-10 9:20 ` Dev Jain
2025-01-10 13:36 ` Dev Jain
2025-01-08 23:31 ` [RFC 10/11] khugepaged: remove max_ptes_none restriction on the pmd scan Nico Pache
2025-01-08 23:31 ` [RFC 11/11] khugepaged: skip collapsing mTHP to smaller orders Nico Pache
2025-01-09 6:22 ` [RFC 00/11] khugepaged: mTHP support Dev Jain
2025-01-10 2:27 ` Nico Pache
2025-01-10 4:56 ` Dev Jain
2025-01-10 22:01 ` Nico Pache
2025-01-12 14:11 ` Dev Jain
2025-01-13 23:00 ` Nico Pache
2025-01-09 6:27 ` Dev Jain
2025-01-10 1:28 ` Nico Pache
2025-01-16 9:47 ` Ryan Roberts
2025-01-16 20:53 ` Nico Pache
2025-01-20 5:17 ` Dev Jain
2025-01-23 20:24 ` Nico Pache
2025-01-24 7:13 ` Dev Jain
2025-01-24 7:38 ` Dev Jain
2025-01-20 12:49 ` Ryan Roberts
2025-01-23 20:42 ` Nico Pache
2025-01-20 12:54 ` David Hildenbrand [this message]
2025-01-20 13:37 ` Ryan Roberts
2025-01-20 13:56 ` David Hildenbrand
2025-01-20 16:27 ` Ryan Roberts
2025-01-20 18:39 ` David Hildenbrand
2025-01-21 9:48 ` Ryan Roberts
2025-01-21 10:19 ` David Hildenbrand
2025-01-27 9:31 ` Dev Jain
2025-01-22 5:18 ` Dev Jain
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