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Wed, 30 Apr 2025 11:43:28 -0700 (PDT) MIME-Version: 1.0 References: <20250428181218.85925-1-npache@redhat.com> <20250428181218.85925-10-npache@redhat.com> In-Reply-To: From: Nico Pache Date: Wed, 30 Apr 2025 12:43:01 -0600 X-Gm-Features: ATxdqUFWtHWq5aUrqZ9Adf9gtcRPQJMwNnkBweD5j20SDmerE4jyu4OMpWWRzi8 Message-ID: Subject: Re: [PATCH v5 09/12] khugepaged: avoid unnecessary mTHP collapse attempts 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, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: kA4MtlQodajERM_2GsCKZmQbLumTOhVCghq9roTAYp8_1746038608 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C6BFF20005 X-Rspam-User: X-Rspamd-Server: rspam07 X-Stat-Signature: 79fs6pourpsyod98xt4iuer9dx1n1ob9 X-HE-Tag: 1746038610-482986 X-HE-Meta: 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 3YcSuMqC WSdesa17QsFkiaiKAsYb0BeUm7Q== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 30, 2025 at 4:12=E2=80=AFAM Baolin Wang wrote: > > > > On 2025/4/29 02:12, Nico Pache wrote: > > There are cases where, if an attempted collapse fails, all subsequent > > orders are guaranteed to also fail. Avoid these collapse attempts by > > bailing out early. > > > > Signed-off-by: Nico Pache > > --- > > mm/khugepaged.c | 17 +++++++++++++++++ > > 1 file changed, 17 insertions(+) > > > > diff --git a/mm/khugepaged.c b/mm/khugepaged.c > > index 86d1153ce9e8..5e6732cccb86 100644 > > --- a/mm/khugepaged.c > > +++ b/mm/khugepaged.c > > @@ -1365,6 +1365,23 @@ static int khugepaged_scan_bitmap(struct mm_stru= ct *mm, unsigned long address, > > collapsed +=3D (1 << order); > > continue; > > } > > + /* > > + * Some ret values indicate all lower order will = also > > + * fail, dont trying to collapse smaller orders > > + */ > > + if (ret =3D=3D SCAN_EXCEED_NONE_PTE || > > + ret =3D=3D SCAN_EXCEED_SWAP_PTE || > > + ret =3D=3D SCAN_EXCEED_SHARED_PTE || > > + ret =3D=3D SCAN_PTE_NON_PRESENT || > > + ret =3D=3D SCAN_PTE_UFFD_WP || > > + ret =3D=3D SCAN_ALLOC_HUGE_PAGE_FAIL || > > + ret =3D=3D SCAN_CGROUP_CHARGE_FAIL || > > + ret =3D=3D SCAN_COPY_MC || > > + ret =3D=3D SCAN_PAGE_LOCK || > > + ret =3D=3D SCAN_PAGE_COUNT) > > + goto next; > > + else > > + break; > > Better to merge this patch into patch 6, which can be helped to > understand your logic. Sounds good, it wasnt part of the original logic/RFCs so i separated it out to get some review on it. >