From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 9CB9F23908C for ; Mon, 3 Mar 2025 22:56:29 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741042589; cv=none; b=kLXPj3TjR4gB0hr8eVh2gIafSpllVsZ+pYHhyBj+hYVrYVL2Tz/Sihu/bdqWFBv9k+VqxHMC1yVvNKXSeldki39jnI8gV0S56hI4BUGFnoZbueSZ8QPOUg0TKCVxMWvmwhEc7aeS7mjm8pRGuFIWBDJg6DK+onVHiOqtbfCtRZ8= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741042589; c=relaxed/simple; bh=OzCMQbtn6cX3CUD0iwKdZeN/h3T7gZrocLCeriwyg6w=; h=Date:To:From:Subject:Message-Id; b=sZXc9WVUwI+Q/2Qhs84Ec6s8yP5PHXk5dvE+WZcM5yJtLHAZw4N9BFLRNgUNJaWJOAQpVE68lq2uZ++pOJ0I5X3t44N6R/g+NW+n6jTEoZNMzoqFO3Ji9JC9Ml8JSBrRnhPWRaq0A/DLHTNK5Pg4bmakat6K+shsuR4xEYKK7Ys= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=hxRlESTI; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="hxRlESTI" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 107B6C4CEEA; Mon, 3 Mar 2025 22:56:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1741042589; bh=OzCMQbtn6cX3CUD0iwKdZeN/h3T7gZrocLCeriwyg6w=; h=Date:To:From:Subject:From; b=hxRlESTILZCESeMHLebgvQ09VzsGhbmwV92/7Xn2VS2U0DrdNkfUn9ajYEjl+X7GW G3diyvywjFN5yB0amcm4v4lA+o/AvGZLA1wfZ5GYjY40YnhobVQ3E1PVS67/eoOV5m 4697SCq4lfxeAyvRgXAp3uil8NNkJSgNOYNXyC9k= Date: Mon, 03 Mar 2025 14:56:28 -0800 To: mm-commits@vger.kernel.org,willy@infradead.org,vbabka@suse.cz,tj@kernel.org,tglx@linutronix.de,muchun.song@linux.dev,mkoutny@suse.com,mingo@redhat.com,luto@kernel.org,lorenzo.stoakes@oracle.com,lizefan.x@bytedance.com,liam.howlett@oracle.com,kirill.shutemov@linux.intel.com,jannh@google.com,ioworker0@gmail.com,hannes@cmpxchg.org,dave.hansen@linux.intel.com,corbet@lwn.net,bp@alien8.de,david@redhat.com,akpm@linux-foundation.org From: Andrew Morton Subject: + fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-pm_mmap_exclusive-config_no_page_mapcount.patch added to mm-unstable branch Message-Id: <20250303225629.107B6C4CEEA@smtp.kernel.org> Precedence: bulk X-Mailing-List: mm-commits@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: The patch titled Subject: fs/proc/task_mmu: remove per-page mapcount dependency for PM_MMAP_EXCLUSIVE (CONFIG_NO_PAGE_MAPCOUNT) has been added to the -mm mm-unstable branch. Its filename is fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-pm_mmap_exclusive-config_no_page_mapcount.patch This patch will shortly appear at https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-pm_mmap_exclusive-config_no_page_mapcount.patch This patch will later appear in the mm-unstable branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** The -mm tree is included into linux-next via the mm-everything branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm and is updated there every 2-3 working days ------------------------------------------------------ From: David Hildenbrand Subject: fs/proc/task_mmu: remove per-page mapcount dependency for PM_MMAP_EXCLUSIVE (CONFIG_NO_PAGE_MAPCOUNT) Date: Mon, 3 Mar 2025 17:30:10 +0100 Let's implement an alternative when per-page mapcounts in large folios are no longer maintained -- soon with CONFIG_NO_PAGE_MAPCOUNT. PM_MMAP_EXCLUSIVE will now be set if folio_likely_mapped_shared() is true -- when the folio is considered "mapped shared", including when it once was "mapped shared" but no longer is, as documented. This might result in and under-indication of "exclusively mapped", which is considered better than over-indicating it: under-estimating the USS (Unique Set Size) is better than over-estimating it. As an alternative, we could simply remove that flag with CONFIG_NO_PAGE_MAPCOUNT completely, but there might be value to it. So, let's keep it like that and document the behavior. Link: https://lkml.kernel.org/r/20250303163014.1128035-18-david@redhat.com Signed-off-by: David Hildenbrand Cc: Andy Lutomirks^H^Hski Cc: Borislav Betkov Cc: Dave Hansen Cc: Ingo Molnar Cc: Jann Horn Cc: Johannes Weiner Cc: Jonathan Corbet Cc: Kirill A. Shutemov Cc: Lance Yang Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Matthew Wilcow (Oracle) Cc: Michal Koutn Cc: Muchun Song Cc: tejun heo Cc: Thomas Gleixner Cc: Vlastimil Babka Cc: Zefan Li Signed-off-by: Andrew Morton --- Documentation/admin-guide/mm/pagemap.rst | 11 +++++++++++ fs/proc/task_mmu.c | 11 +++++++++-- 2 files changed, 20 insertions(+), 2 deletions(-) --- a/Documentation/admin-guide/mm/pagemap.rst~fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-pm_mmap_exclusive-config_no_page_mapcount +++ a/Documentation/admin-guide/mm/pagemap.rst @@ -38,6 +38,17 @@ There are four components to pagemap: precisely which pages are mapped (or in swap) and comparing mapped pages between processes. + Traditionally, bit 56 indicates that a page is mapped exactly once and bit + 56 is clear when a page is mapped multiple times, even when mapped in the + same process multiple times. In some kernel configurations, the semantics + for pages part of a larger allocation (e.g., THP) can differ: bit 56 is set + if all pages part of the corresponding large allocation are *certainly* + mapped in the same process, even if the page is mapped multiple times in that + process. Bit 56 is clear when any page page of the larger allocation + is *maybe* mapped in a different process. In some cases, a large allocation + might be treated as "maybe mapped by multiple processes" even though this + is no longer the case. + Efficient users of this interface will use ``/proc/pid/maps`` to determine which areas of memory are actually mapped and llseek to skip over unmapped regions. --- a/fs/proc/task_mmu.c~fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-pm_mmap_exclusive-config_no_page_mapcount +++ a/fs/proc/task_mmu.c @@ -1652,6 +1652,13 @@ static int add_to_pagemap(pagemap_entry_ return 0; } +static bool __folio_page_mapped_exclusively(struct folio *folio, struct page *page) +{ + if (IS_ENABLED(CONFIG_PAGE_MAPCOUNT)) + return folio_precise_page_mapcount(folio, page) == 1; + return !folio_maybe_mapped_shared(folio); +} + static int pagemap_pte_hole(unsigned long start, unsigned long end, __always_unused int depth, struct mm_walk *walk) { @@ -1742,7 +1749,7 @@ static pagemap_entry_t pte_to_pagemap_en if (!folio_test_anon(folio)) flags |= PM_FILE; if ((flags & PM_PRESENT) && - folio_precise_page_mapcount(folio, page) == 1) + __folio_page_mapped_exclusively(folio, page)) flags |= PM_MMAP_EXCLUSIVE; } if (vma->vm_flags & VM_SOFTDIRTY) @@ -1817,7 +1824,7 @@ static int pagemap_pmd_range(pmd_t *pmdp pagemap_entry_t pme; if (folio && (flags & PM_PRESENT) && - folio_precise_page_mapcount(folio, page + idx) == 1) + __folio_page_mapped_exclusively(folio, page)) cur_flags |= PM_MMAP_EXCLUSIVE; pme = make_pme(frame, cur_flags); _ Patches currently in -mm which might be from david@redhat.com are mm-gup-reject-foll_split_pmd-with-hugetlb-vmas.patch mm-rmap-reject-hugetlb-folios-in-folio_make_device_exclusive.patch mm-rmap-convert-make_device_exclusive_range-to-make_device_exclusive.patch mm-rmap-convert-make_device_exclusive_range-to-make_device_exclusive-fix.patch mm-rmap-implement-make_device_exclusive-using-folio_walk-instead-of-rmap-walk.patch mm-memory-detect-writability-in-restore_exclusive_pte-through-can_change_pte_writable.patch mm-use-single-swp_device_exclusive-entry-type.patch mm-page_vma_mapped-device-exclusive-entries-are-not-migration-entries.patch kernel-events-uprobes-handle-device-exclusive-entries-correctly-in-__replace_page.patch mm-ksm-handle-device-exclusive-entries-correctly-in-write_protect_page.patch mm-rmap-handle-device-exclusive-entries-correctly-in-try_to_unmap_one.patch mm-rmap-handle-device-exclusive-entries-correctly-in-try_to_migrate_one.patch mm-rmap-handle-device-exclusive-entries-correctly-in-page_vma_mkclean_one.patch mm-page_idle-handle-device-exclusive-entries-correctly-in-page_idle_clear_pte_refs_one.patch mm-damon-handle-device-exclusive-entries-correctly-in-damon_folio_young_one.patch mm-damon-handle-device-exclusive-entries-correctly-in-damon_folio_mkold_one.patch mm-rmap-keep-mapcount-untouched-for-device-exclusive-entries.patch mm-rmap-avoid-ebusy-from-make_device_exclusive.patch lib-test_hmm-make-dmirror_atomic_map-consume-a-single-page.patch mm-memory-remove-pageanonexclusive-sanity-check-in-restore_exclusive_pte.patch mm-memory-pass-folio-and-pte-to-restore_exclusive_pte.patch mm-memory-document-restore_exclusive_pte.patch mm-mmu_notifier-use-mmu_notify_clear-in-remove_device_exclusive_entry.patch mm-factor-out-large-folio-handling-from-folio_order-into-folio_large_order.patch mm-factor-out-large-folio-handling-from-folio_nr_pages-into-folio_large_nr_pages.patch mm-let-_folio_nr_pages-overlay-memcg_data-in-first-tail-page.patch mm-move-hugetlb-specific-things-in-folio-to-page.patch mm-move-_pincount-in-folio-to-page-on-32bit.patch mm-move-_entire_mapcount-in-folio-to-page-on-32bit.patch mm-rmap-pass-dst_vma-to-folio_dup_file_rmap_pte-and-friends.patch mm-rmap-pass-vma-to-__folio_add_rmap.patch mm-rmap-abstract-large-mapcount-operations-for-large-folios-hugetlb.patch bit_spinlock-__always_inline-unlock-functions.patch mm-rmap-use-folio_large_nr_pages-in-add-remove-functions.patch mm-rmap-basic-mm-owner-tracking-for-large-folios-hugetlb.patch mm-copy-on-write-cow-reuse-support-for-pte-mapped-thp.patch mm-convert-folio_likely_mapped_shared-to-folio_maybe_mapped_shared.patch mm-config_no_page_mapcount-to-prepare-for-not-maintain-per-page-mapcounts-in-large-folios.patch fs-proc-page-remove-per-page-mapcount-dependency-for-proc-kpagecount-config_no_page_mapcount.patch fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-pm_mmap_exclusive-config_no_page_mapcount.patch fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-mapmax-config_no_page_mapcount.patch fs-proc-task_mmu-remove-per-page-mapcount-dependency-for-smaps-smaps_rollup-config_no_page_mapcount.patch mm-stop-maintaining-the-per-page-mapcount-of-large-folios-config_no_page_mapcount.patch