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Tue, 09 Sep 2025 23:18:23 -0700 (PDT) MIME-Version: 1.0 References: <20250910024447.64788-1-laoar.shao@gmail.com> <20250910024447.64788-2-laoar.shao@gmail.com> <7c890b42-610f-42ec-acf2-b5b9f95209b1@linux.dev> In-Reply-To: <7c890b42-610f-42ec-acf2-b5b9f95209b1@linux.dev> From: Yafang Shao Date: Wed, 10 Sep 2025 14:17:47 +0800 X-Gm-Features: AS18NWAEtXjJHwi77ZRJ7QtvbBT2n7zXaHBMPXJVp87PMZaJZ2j5bODmbGmPrA0 Message-ID: Subject: Re: [PATCH v7 mm-new 01/10] mm: thp: remove disabled task from khugepaged_mm_slot To: Lance Yang , Andrew Morton , David Hildenbrand Cc: bpf@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org, Lance Yang , baolin.wang@linux.alibaba.com, ziy@nvidia.com, hannes@cmpxchg.org, corbet@lwn.net, ameryhung@gmail.com, 21cnbao@gmail.com, shakeel.butt@linux.dev, rientjes@google.com, andrii@kernel.org, daniel@iogearbox.net, ast@kernel.org, ryan.roberts@arm.com, gutierrez.asier@huawei-partners.com, willy@infradead.org, usamaarif642@gmail.com, lorenzo.stoakes@oracle.com, npache@redhat.com, dev.jain@arm.com, Liam.Howlett@oracle.com Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspamd-Queue-Id: C9E4410000F X-Rspamd-Server: rspam05 X-Stat-Signature: jp9pme9yr8ettep7cof876fuz7orp1qk X-Rspam-User: X-HE-Tag: 1757485104-992124 X-HE-Meta: U2FsdGVkX1+CO4wuKNEQ+ee0yX2FH5tGsdRvKTskaB4YZGa9AF27KLCa7HOX7ToZ0lcjzbtV+sGVgJO8lR4+dsyqbaJk3bdoQf/IwZR0RrJ75o/GHadv8VWd2J1Dfyq7VJPQkw7u2fHth9KjcptI9RneRfkqklLKMlOEcy6cAmbL3JKaj4qzjF5mdk0jqUqUkNb4pRyKddwrv5XxtUTXT1XYN2t8LoS8fkidFtLfLhHdIPxhXOXJI28OWfKg9p0Bri6QIII23NxByLslLdCLhsswk0HGDzaD5PPZleNtRVEiJyg74salVE47n0YAusYWPxBRYXY2bUGwnaG9loRj23jYWjN/2SzzpqpRU3jzwpHzFUYB/jIX2B04PTjNSrMbf6eiXoiEN2lCW8wmz0h11Z8HfAvKIEeFAAZvVugFkEHRRf8g927Kt1L9GAvYcKv741I8FR3H2Wpt9bcKPab7A2df0b3XHVZNTObeekua02NXqzUh979eWCpXHGPH4byAZLUja6B7O9gZ25a/fW499a90BSQ8GO7/gBbdJwqulHzyJXjkJpgJ52K2qPELPtsmZvmkSVP8Cm0VRFWeqIx11PGGioadUNAswmpmJTW71oPTVon+hA3lumhedP2vvM6O7OmCpcCPVJmH9GJxVg3lfoXwR4dr0KsLhHC5xtGKe6Ep4Y2S7mylDg1N2Auhh4K2w0zRW05yZCJ46RkNj6QOgj9B8hTGVgCFhKQogl9HfOlague/hKhRqf8UbjK89SfW76c8dvyj7f69gY/5zG2Fum7rvaH9FdYrCtoi5dSZ8JNiXS9sgDXDxqJodTR2d/t47B7x7EvXJfJzgA94N0YWH50OmcFr1tePjBC+J3fvA63KizuoLnm0Tt/VEv0fXqcdAhfJoKtOBNjaS8KthjrCHcdPA19O27a9XtBXHY7TGZKw/SEZJIfqKTKRmWLoIK9nfoGHxfjfBpSENErV5Hv +PDlpQaw 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 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, Sep 10, 2025 at 1:11=E2=80=AFPM Lance Yang w= rote: > > Hey Yafang, > > On 2025/9/10 10:44, Yafang Shao wrote: > > Since a task with MMF_DISABLE_THP_COMPLETELY cannot use THP, remove it = from > > the khugepaged_mm_slot to stop khugepaged from processing it. > > > > After this change, the following semantic relationship always holds: > > > > MMF_VM_HUGEPAGE is set =3D=3D task is in khugepaged mm_slot > > MMF_VM_HUGEPAGE is not set =3D=3D task is not in khugepaged mm_slot > > > > Signed-off-by: Yafang Shao > > Cc: Lance Yang > > --- > > include/linux/khugepaged.h | 1 + > > kernel/sys.c | 6 ++++++ > > mm/khugepaged.c | 19 +++++++++---------- > > 3 files changed, 16 insertions(+), 10 deletions(-) > > > > diff --git a/include/linux/khugepaged.h b/include/linux/khugepaged.h > > index eb1946a70cff..6cb9107f1006 100644 > > --- a/include/linux/khugepaged.h > > +++ b/include/linux/khugepaged.h > > @@ -19,6 +19,7 @@ extern void khugepaged_min_free_kbytes_update(void); > > extern bool current_is_khugepaged(void); > > extern int collapse_pte_mapped_thp(struct mm_struct *mm, unsigned lon= g addr, > > bool install_pmd); > > +bool hugepage_pmd_enabled(void); > > > > static inline void khugepaged_fork(struct mm_struct *mm, struct mm_st= ruct *oldmm) > > { > > diff --git a/kernel/sys.c b/kernel/sys.c > > index a46d9b75880b..a1c1e8007f2d 100644 > > --- a/kernel/sys.c > > +++ b/kernel/sys.c > > @@ -8,6 +8,7 @@ > > #include > > #include > > #include > > +#include > > #include > > #include > > #include > > @@ -2493,6 +2494,11 @@ static int prctl_set_thp_disable(bool thp_disabl= e, unsigned long flags, > > mm_flags_clear(MMF_DISABLE_THP_COMPLETELY, mm); > > mm_flags_clear(MMF_DISABLE_THP_EXCEPT_ADVISED, mm); > > } > > + > > + if (!mm_flags_test(MMF_DISABLE_THP_COMPLETELY, mm) && > > + !mm_flags_test(MMF_VM_HUGEPAGE, mm) && > > + hugepage_pmd_enabled()) > > + __khugepaged_enter(mm); > > mmap_write_unlock(current->mm); > > One minor style suggestion for prctl_set_thp_disable(): > > static int prctl_set_thp_disable(bool thp_disable, unsigned long flags, > unsigned long arg4, unsigned long arg5) > { > struct mm_struct *mm =3D current->mm; > > [...] > if (mmap_write_lock_killable(current->mm)) > return -EINTR; > [...] > mmap_write_unlock(current->mm); > return 0; > } > > It initializes struct mm_struct *mm =3D current->mm; at the beginning, bu= t > then uses both mm and current->mm. Could you change the calls using > current->mm to use the local mm variable for consistency? Just a nit ;) Nice catch Hello Andrew, David, The original commit "prctl: extend PR_SET_THP_DISABLE to optionally exclude VM_HUGEPAGE" is still in mm-new branch. The change below is a minor cleanup for it. Could we please fold this change directly into the original commit to keep the history clean? diff --git a/kernel/sys.c b/kernel/sys.c index a46d9b7..2250a32 100644 --- a/kernel/sys.c +++ b/kernel/sys.c @@ -2479,7 +2479,7 @@ static int prctl_set_thp_disable(bool thp_disable, unsigned long flags, /* Flags are only allowed when disabling. */ if ((!thp_disable && flags) || (flags & ~PR_THP_DISABLE_EXCEPT_ADVI= SED)) return -EINVAL; - if (mmap_write_lock_killable(current->mm)) + if (mmap_write_lock_killable(mm)) return -EINTR; if (thp_disable) { if (flags & PR_THP_DISABLE_EXCEPT_ADVISED) { @@ -2493,7 +2493,7 @@ static int prctl_set_thp_disable(bool thp_disable, unsigned long flags, mm_flags_clear(MMF_DISABLE_THP_COMPLETELY, mm); mm_flags_clear(MMF_DISABLE_THP_EXCEPT_ADVISED, mm); } - mmap_write_unlock(current->mm); + mmap_write_unlock(mm); return 0; } --=20 Regards Yafang