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Tue, 13 Jan 2026 18:39:06 -0800 (PST) X-Received: by 2002:a53:b199:0:b0:63f:9928:3f85 with SMTP id 956f58d0204a3-64901b01ee2mr778884d50.62.1768358345750; Tue, 13 Jan 2026 18:39:05 -0800 (PST) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <20251201174627.23295-1-npache@redhat.com> <20251201174627.23295-6-npache@redhat.com> In-Reply-To: From: Nico Pache Date: Tue, 13 Jan 2026 19:38:39 -0700 X-Gm-Features: AZwV_Qg4QcCHsWf9Yf2aqPxUCcKE6236uDrcuWobRoGZDAiQfOTpw9hN9JUYA5U Message-ID: Subject: Re: [PATCH v13 mm-new 05/16] khugepaged: introduce is_mthp_order helper To: Zi Yan , Lorenzo Stoakes Cc: linux-kernel@vger.kernel.org, linux-trace-kernel@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, david@redhat.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, dev.jain@arm.com, corbet@lwn.net, rostedt@goodmis.org, mhiramat@kernel.org, mathieu.desnoyers@efficios.com, akpm@linux-foundation.org, baohua@kernel.org, willy@infradead.org, peterx@redhat.com, wangkefeng.wang@huawei.com, usamaarif642@gmail.com, sunnanyong@huawei.com, vishal.moola@gmail.com, thomas.hellstrom@linux.intel.com, yang@os.amperecomputing.com, kas@kernel.org, aarcange@redhat.com, raquini@redhat.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, hughd@google.com, richard.weiyang@gmail.com, lance.yang@linux.dev, vbabka@suse.cz, rppt@kernel.org, jannh@google.com, pfalcato@suse.de Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Tue, Dec 2, 2025 at 8:13=E2=80=AFPM Zi Yan wrote: > > On 1 Dec 2025, at 12:46, Nico Pache wrote: > > > In order to add mTHP support, we will often be checking if a given orde= r > > is a mTHP or PMD order. Lets create a simple helper function to keep th= e > > code clean and readable. > > > > Suggested-by: Lorenzo Stoakes > > Signed-off-by: Nico Pache > > --- > > mm/khugepaged.c | 9 +++++++-- > > 1 file changed, 7 insertions(+), 2 deletions(-) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index 8599c7fa112e..9c041141b2e3 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -338,6 +338,11 @@ static bool pte_none_or_zero(pte_t pte) > > return pte_present(pte) && is_zero_pfn(pte_pfn(pte)); > > } > > > > +static bool is_mthp_order(unsigned int order) > > +{ > > + return order !=3D HPAGE_PMD_ORDER; > > +} > > + > > The code at the bottom of __folio_split() in mm/huge_memory.c > can use this helper. > > The code in deferred_split_folio() uses folio_test_pmd_mappable() > instead of order =3D=3D HPAGE_PMD_ORDER, but the code can be changed > to use the helper. static inline bool folio_test_pmd_mappable(struct folio *folio) { return folio_order(folio) >=3D HPAGE_PMD_ORDER; } Should we make the is_mthp_order() check all orders that are less than HPAGE_PMD_ORDER. ie) +static bool is_mthp_order(unsigned int order) +{ + return order < HPAGE_PMD_ORDER; } This way it's true to its mTHP nature being smaller than the PMD. Cheers, -- Nico > > > int hugepage_madvise(struct vm_area_struct *vma, > > vm_flags_t *vm_flags, int advice) > > { > > @@ -1071,13 +1076,13 @@ static int alloc_charge_folio(struct folio **fo= liop, struct mm_struct *mm, > > folio =3D __folio_alloc(gfp, order, node, &cc->alloc_nmask); > > if (!folio) { > > *foliop =3D NULL; > > - if (order =3D=3D HPAGE_PMD_ORDER) > > + if (!is_mthp_order(order)) > > count_vm_event(THP_COLLAPSE_ALLOC_FAILED); > > count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC_FAILED); > > return SCAN_ALLOC_HUGE_PAGE_FAIL; > > } > > > > - if (order =3D=3D HPAGE_PMD_ORDER) > > + if (!is_mthp_order(order)) > > count_vm_event(THP_COLLAPSE_ALLOC); > > count_mthp_stat(order, MTHP_STAT_COLLAPSE_ALLOC); > > > > -- > > 2.51.1 > > > Best Regards, > Yan, Zi >