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Wed, 23 Apr 2025 00:06:28 -0700 (PDT) X-Google-Smtp-Source: AGHT+IFn1zWiBl7mj2ZHMbPzEt4TQGJA7ZA52O1IykfzgHQk9rLrJ75DUXlgd4SeW7i6QSPYXTpfssBeJp5N7K7bY+g= X-Received: by 2002:a05:6902:c10:b0:e6d:f41c:6bdb with SMTP id 3f1490d57ef6-e7297d93324mr23626241276.6.1745391987773; Wed, 23 Apr 2025 00:06:27 -0700 (PDT) Precedence: bulk X-Mailing-List: linux-trace-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20250417000238.74567-1-npache@redhat.com> <20250417000238.74567-2-npache@redhat.com> In-Reply-To: From: Nico Pache Date: Wed, 23 Apr 2025 01:06:01 -0600 X-Gm-Features: ATxdqUHpjU8S0MShRUQwhPVFS5hZ7SZaiRUxbW-9PYZFjeXZxNqacPcUS1Nsk1c Message-ID: Subject: Re: [PATCH v4 01/12] introduce khugepaged_collapse_single_pmd to unify khugepaged and madvise_collapse To: Baolin Wang Cc: linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, akpm@linux-foundation.org, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, david@redhat.com, baohua@kernel.org, ryan.roberts@arm.com, willy@infradead.org, peterx@redhat.com, ziy@nvidia.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kirill.shutemov@linux.intel.com, aarcange@redhat.com, raquini@redhat.com, dev.jain@arm.com, anshuman.khandual@arm.com, catalin.marinas@arm.com, tiwai@suse.de, will@kernel.org, dave.hansen@linux.intel.com, jack@suse.cz, cl@gentwo.org, jglisse@google.com, surenb@google.com, zokeefe@google.com, hannes@cmpxchg.org, rientjes@google.com, mhocko@suse.com, rdunlap@infradead.org X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: JutKwxS5K-m9jz2btxhuSDs514sFolQg0xNYYSd9vok_1745391988 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Wed, Apr 23, 2025 at 12:44=E2=80=AFAM Baolin Wang wrote: > > > > On 2025/4/17 08:02, 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 > > Can you add a prefix 'khugepaged:' for the subject line? I had that originally but the subject line is already extremely long. > > > --- > > mm/khugepaged.c | 92 ++++++++++++++++++++++++------------------------= - > > 1 file changed, 46 insertions(+), 46 deletions(-) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index b8838ba8207a..cecadc4239e7 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -2363,6 +2363,48 @@ static int hpage_collapse_scan_file(struct mm_st= ruct *mm, unsigned long addr, > > } > > #endif > > > > +/* > > + * Try to collapse a single PMD starting at a PMD aligned addr, and re= turn > > + * the results. > > + */ > > +static int khugepaged_collapse_single_pmd(unsigned long addr, > > + struct vm_area_struct *vma, bool *mmap= _locked, > > + struct collapse_control *cc) > > +{ > > + int result =3D SCAN_FAIL; > > + struct mm_struct *mm =3D vma->vm_mm; > > + unsigned long tva_flags =3D cc->is_khugepaged ? TVA_ENFORCE_SYSFS= : 0; > > + > > + if (thp_vma_allowable_order(vma, vma->vm_flags, > > + tva_flags, PMD_ORDER)) { > > We've already checked the thp_vma_allowable_order() before calling this > function, why check again? > > > + if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous(vma)) { > > + struct file *file =3D get_file(vma->vm_file); > > + pgoff_t pgoff =3D linear_page_index(vma, addr); > > + > > + mmap_read_unlock(mm); > > + *mmap_locked =3D false; > > + result =3D hpage_collapse_scan_file(mm, addr, fil= e, pgoff, > > + cc); > > + fput(file); > > + if (result =3D=3D SCAN_PTE_MAPPED_HUGEPAGE) { > > + mmap_read_lock(mm); > > + if (hpage_collapse_test_exit_or_disable(m= m)) > > + goto end; > > + result =3D collapse_pte_mapped_thp(mm, ad= dr, > > + !cc->is_= khugepaged); > > why drop the following check? > if (*result =3D=3D SCAN_PMD_MAPPED) > *result =3D SCAN_SUCCEED; Good catch! When generalizing this for madvise_collapse i forgot to properly handle the khugepaged case of PMD_MAPPED=3D=3DSUCCEED. > > > + mmap_read_unlock(mm); > > + } > > + } else { > > + result =3D hpage_collapse_scan_pmd(mm, vma, addr, > > + mmap_locked, cc)= ; > > + } > > + if (cc->is_khugepaged && result =3D=3D SCAN_SUCCEED) > > + ++khugepaged_pages_collapsed; > > + } > > +end: > > + return result; > > +} > > + > > static unsigned int khugepaged_scan_mm_slot(unsigned int pages, int *= result, > > struct collapse_control *cc) > > __releases(&khugepaged_mm_lock) > > @@ -2437,33 +2479,9 @@ static unsigned int khugepaged_scan_mm_slot(unsi= gned int pages, int *result, > > VM_BUG_ON(khugepaged_scan.address < hstart || > > khugepaged_scan.address + HPAGE_PMD_SIZ= E > > > hend); > > - if (IS_ENABLED(CONFIG_SHMEM) && !vma_is_anonymous= (vma)) { > > - struct file *file =3D get_file(vma->vm_fi= le); > > - pgoff_t pgoff =3D linear_page_index(vma, > > - khugepaged_scan.address); > > > > - mmap_read_unlock(mm); > > - mmap_locked =3D false; > > - *result =3D hpage_collapse_scan_file(mm, > > - khugepaged_scan.address, file, pg= off, cc); > > - fput(file); > > - if (*result =3D=3D SCAN_PTE_MAPPED_HUGEPA= GE) { > > - mmap_read_lock(mm); > > - if (hpage_collapse_test_exit_or_d= isable(mm)) > > - goto breakouterloop; > > - *result =3D collapse_pte_mapped_t= hp(mm, > > - khugepaged_scan.address, = false); > > - if (*result =3D=3D SCAN_PMD_MAPPE= D) > > - *result =3D SCAN_SUCCEED; > > - mmap_read_unlock(mm); > > - } > > - } else { > > - *result =3D hpage_collapse_scan_pmd(mm, v= ma, > > - khugepaged_scan.address, &mmap_lo= cked, cc); > > - } > > - > > - if (*result =3D=3D SCAN_SUCCEED) > > - ++khugepaged_pages_collapsed; > > + *result =3D khugepaged_collapse_single_pmd(khugep= aged_scan.address, > > + vma, &mmap_locked, cc); > > If the khugepaged_collapse_single_pmd() returns a failure caused by > hpage_collapse_test_exit_or_disable(), we should break out of the loop > according to the original logic. But you've changed the action in this > patch, is this intentional? Nope, not intentional! Thanks for pointing that out. I'll get that fixed! Thanks for the in depth review ! I'll work on cleaning up these corner case= s. > > > > > /* move to next address */ > > khugepaged_scan.address +=3D HPAGE_PMD_SIZE; > > @@ -2783,36 +2801,18 @@ 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 =3D get_file(vma->vm_file); > > - pgoff_t pgoff =3D linear_page_index(vma, addr); > > > > - mmap_read_unlock(mm); > > - mmap_locked =3D false; > > - result =3D hpage_collapse_scan_file(mm, addr, fil= e, pgoff, > > - cc); > > - fput(file); > > - } else { > > - result =3D hpage_collapse_scan_pmd(mm, vma, addr, > > - &mmap_locked, cc= ); > > - } > > + result =3D khugepaged_collapse_single_pmd(addr, vma, &mma= p_locked, cc); > > + > > if (!mmap_locked) > > *prev =3D NULL; /* Tell caller we dropped mmap_l= ock */ > > > > -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 =3D 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: >