From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 254FC198E60; Tue, 18 Feb 2025 16:26:10 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739895974; cv=none; b=JZQcu8eLU7JtjJ8hmvQC4y4npmu9OfoB1Zf+asnKVBnFH1cGmLNmBZeuiinzLbe6neuXnT8B/G6Gi4ZuVFwXJrz+LQssYZnC53NRqTr0a4RE5n6GE/ioEvnSNdGil+AhKcisatISAqXJSbOn/4NQZzShxmQXayBCeJ7snn1P7hA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1739895974; c=relaxed/simple; bh=mAKKpLK8tkLsblSxhjdkSQA7q+BNXVXYxQw89MAWpxg=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=YSXExnqZuxjf/g8axdk0ZQIkiJ1cEi0rEabpM17wQ143H+NUi8VSUdvWUcj52T2Sq5YH2Di5KTBklF/LwllyboVPrC4G/9n2rhvNBaYXzfRT928ofZ3xVA8tnXVq7zHNKj3xXRC72ALN/B7+ST78SZORROm/Q2B2827n7Q3UdzE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id C6C54152B; Tue, 18 Feb 2025 08:26:28 -0800 (PST) Received: from [10.1.27.186] (XHFQ2J9959.cambridge.arm.com [10.1.27.186]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 364EB3F59E; Tue, 18 Feb 2025 08:26:04 -0800 (PST) Message-ID: <8d1fed22-5ba8-433b-9ef9-478b337b10d5@arm.com> Date: Tue, 18 Feb 2025 16:26:02 +0000 Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC v2 1/9] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse Content-Language: en-GB To: Nico Pache , linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org Cc: 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, david@redhat.com, aarcange@redhat.com, raquini@redhat.com, dev.jain@arm.com, sunnanyong@huawei.com, usamaarif642@gmail.com, audra@redhat.com, akpm@linux-foundation.org, rostedt@goodmis.org, mathieu.desnoyers@efficios.com, tiwai@suse.de References: <20250211003028.213461-1-npache@redhat.com> <20250211003028.213461-2-npache@redhat.com> From: Ryan Roberts In-Reply-To: <20250211003028.213461-2-npache@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 11/02/2025 00:30, Nico Pache wrote: > The khugepaged daemon and madvise_collapse have two different > implementations that do almost the same thing. > > Create khugepaged_collapse_single_pmd to increase code > reuse and create an entry point for future khugepaged changes. > > Refactor madvise_collapse and khugepaged_scan_mm_slot to use > the new khugepaged_collapse_single_pmd function. > > Signed-off-by: Nico Pache > --- > mm/khugepaged.c | 96 +++++++++++++++++++++++++------------------------ > 1 file changed, 50 insertions(+), 46 deletions(-) > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > index 5f0be134141e..46faee67378b 100644 > --- a/mm/khugepaged.c > +++ b/mm/khugepaged.c > @@ -2365,6 +2365,52 @@ static int hpage_collapse_scan_file(struct mm_struct *mm, unsigned long addr, > } > #endif > > +/* > + * Try to collapse a single PMD starting at a PMD aligned addr, and return > + * the results. > + */ > +static int khugepaged_collapse_single_pmd(unsigned long addr, struct mm_struct *mm, > + struct vm_area_struct *vma, bool *mmap_locked, > + struct collapse_control *cc) nit: given the vma links to the mm is it really neccessary to pass both? Why not just pass vma? > +{ > + int result = SCAN_FAIL; > + unsigned long tva_flags = cc->is_khugepaged ? TVA_ENFORCE_SYSFS : 0; > + > + if (!*mmap_locked) { > + mmap_read_lock(mm); > + *mmap_locked = true; > + } AFAICT, the read lock is always held when khugepaged_collapse_single_pmd() is called. Perhaps VM_WARN_ON(!*mmap_locked) would be more appropriate? > + > + if (thp_vma_allowable_order(vma, vma->vm_flags, > + tva_flags, PMD_ORDER)) { > + if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) { I guess it was like this before, but what's the relevance of CONFIG_SHMEM? Surely this should work for any file if CONFIG_READ_ONLY_THP_FOR_FS is enabled? > + struct file *file = get_file(vma->vm_file); > + pgoff_t pgoff = linear_page_index(vma, addr); > + > + mmap_read_unlock(mm); > + *mmap_locked = false; > + result = hpage_collapse_scan_file(mm, addr, file, pgoff, > + cc); > + fput(file); > + if (result == SCAN_PTE_MAPPED_HUGEPAGE) { > + mmap_read_lock(mm); > + if (hpage_collapse_test_exit_or_disable(mm)) > + goto end; > + result = collapse_pte_mapped_thp(mm, addr, > + !cc->is_khugepaged); > + mmap_read_unlock(mm); > + } > + } else { > + result = hpage_collapse_scan_pmd(mm, vma, addr, > + mmap_locked, cc); > + } > + if (result == SCAN_SUCCEED || result == SCAN_PMD_MAPPED) > + ++khugepaged_pages_collapsed; Looks like this counter was previously only incremented for the scan path, not for the madvise_collapse path. Not sure if that's a problem? Thanks, Ryan > + } > +end: > + return result; > +} > + > static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result, > struct collapse_control *cc) > __releases(&khugepaged_mm_lock) > @@ -2439,33 +2485,9 @@ static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *result, > VM_BUG_ON(khugepaged_scan.address < hstart || > khugepaged_scan.address + HPAGE_PMD_SIZE > > hend); > - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) { > - struct file *file = get_file(vma->vm_file); > - pgoff_t pgoff = linear_page_index(vma, > - khugepaged_scan.address); > > - mmap_read_unlock(mm); > - mmap_locked = false; > - *result = hpage_collapse_scan_file(mm, > - khugepaged_scan.address, file, pgoff, cc); > - fput(file); > - if (*result == SCAN_PTE_MAPPED_HUGEPAGE) { > - mmap_read_lock(mm); > - if (hpage_collapse_test_exit_or_disable(mm)) > - goto breakouterloop; > - *result = collapse_pte_mapped_thp(mm, > - khugepaged_scan.address, false); > - if (*result == SCAN_PMD_MAPPED) > - *result = SCAN_SUCCEED; > - mmap_read_unlock(mm); > - } > - } else { > - *result = hpage_collapse_scan_pmd(mm, vma, > - khugepaged_scan.address, &mmap_locked, cc); > - } > - > - if (*result == SCAN_SUCCEED) > - ++khugepaged_pages_collapsed; > + *result = khugepaged_collapse_single_pmd(khugepaged_scan.address, > + mm, vma, &mmap_locked, cc); > > /* move to next address */ > khugepaged_scan.address += HPAGE_PMD_SIZE; > @@ -2785,36 +2807,18 @@ int madvise_collapse(struct vm_area_struct *vma, struct vm_area_struct **prev, > mmap_assert_locked(mm); > memset(cc->node_load, 0, sizeof(cc->node_load)); > nodes_clear(cc->alloc_nmask); > - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) { > - struct file *file = get_file(vma->vm_file); > - pgoff_t pgoff = linear_page_index(vma, addr); > > - mmap_read_unlock(mm); > - mmap_locked = false; > - result = hpage_collapse_scan_file(mm, addr, file, pgoff, > - cc); > - fput(file); > - } else { > - result = hpage_collapse_scan_pmd(mm, vma, addr, > - &mmap_locked, cc); > - } > + result = khugepaged_collapse_single_pmd(addr, mm, vma, &mmap_locked, cc); > + > if (!mmap_locked) > *prev = NULL; /* Tell caller we dropped mmap_lock */ > > -handle_result: > switch (result) { > case SCAN_SUCCEED: > case SCAN_PMD_MAPPED: > ++thps; > break; > case SCAN_PTE_MAPPED_HUGEPAGE: > - BUG_ON(mmap_locked); > - BUG_ON(*prev); > - mmap_read_lock(mm); > - result = collapse_pte_mapped_thp(mm, addr, true); > - mmap_read_unlock(mm); > - goto handle_result; > - /* Whitelisted set of results where continuing OK */ > case SCAN_PMD_NULL: > case SCAN_PTE_NON_PRESENT: > case SCAN_PTE_UFFD_WP: