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AJvYcCWPjkwEJSpXU2OfSFfuGGBpRA5gieD6nVDjTCIhyG0sMQoQfeTET37g2dfU6K2EzFwb7uhjtFQULURaBRUAPr3TFyw= X-Gm-Message-State: AOJu0Yz70M2IGP/uQChq9ihVO/+Nvfl6rOtr2/Z92TQ+QwlI65fWnLEU 5ew1qQeImD61wcIktZnw/Gypf+LogCIS8VCgqGfwu1K4NpB5LPH1nC0omEMeKB0gIA2Jm0jP0zq Xk16R8APIRlppbuFXx8v3DCGpXb4= X-Google-Smtp-Source: AGHT+IHI75h04SIf4Rmmtl46mN7kSxQnN/OGrsFpteG6StVtG1VO6ZHry9J2NeT6hJcXAn65twmP+sjd9qdh36qj3Hc= X-Received: by 2002:a50:99c9:0:b0:578:6901:7454 with SMTP id 4fb4d7f45d1cf-57c5089a10amr487540a12.15.1717725060550; Thu, 06 Jun 2024 18:51:00 -0700 (PDT) MIME-Version: 1.0 References: <20240521040244.48760-1-ioworker0@gmail.com> <20240521040244.48760-3-ioworker0@gmail.com> <758f7be7-c17e-46d1-879f-83340ec85749@redhat.com> <5a728148-ed93-4d68-a86f-9be3612dedbb@redhat.com> <2a6a1b50-e711-42c2-91f4-42881a6057e9@redhat.com> In-Reply-To: <2a6a1b50-e711-42c2-91f4-42881a6057e9@redhat.com> From: Lance Yang Date: Fri, 7 Jun 2024 09:50:49 +0800 Message-ID: Subject: Re: [PATCH v6 2/3] mm/rmap: integrate PMD-mapped folio splitting into pagewalk loop To: David Hildenbrand Cc: akpm@linux-foundation.org, willy@infradead.org, sj@kernel.org, baolin.wang@linux.alibaba.com, maskray@google.com, ziy@nvidia.com, ryan.roberts@arm.com, 21cnbao@gmail.com, mhocko@suse.com, fengwei.yin@intel.com, zokeefe@google.com, shy828301@gmail.com, xiehuan09@gmail.com, libang.li@antgroup.com, wangkefeng.wang@huawei.com, songmuchun@bytedance.com, peterx@redhat.com, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Stat-Signature: z68uof61m3oo3c8fg1z7f58rnt4tfw1q X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 31EEF1A0005 X-HE-Tag: 1717725061-198454 X-HE-Meta: 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 H88VtGIF FzW0xFY98kiGCS+wvpeHY7qfnt/ue5Qtr00Z6aKqSuKh2VCEY4wLlCAreLbxUYvDyuucJMUs6rL74VG1kjO6OA6o7R5cqt4BbS9dM4gx1U7Pt9WTHXFvjXWUj9dwgN6MJetO9H59kf5AnZcC2Wx2XmIBL/ny3cwYX5kuiM34Kvun5nuElsQOwMVEUiueMfjxg/V6YXjBXNm8DgIz1+3AJUOvid7nA6943Lg/MdWkZ76NbfLt++F+LoDuSOy3iClk0hGXb0/SErjpNsVkykE4FBrK09T0ImlsFvashf/Ou/W8QQAFUd5pG/+j4S/3EphWcPRFO3rld1dVoR2Pf+MMWcAejbd2RXRK37yIj0KOQKTfhPLRFKFNxMlZOGq66NWVBI5d2rlb4du56TKLd2RCz4biZF07TB9mq5v4bcZQX8EtoLTM= 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 Thu, Jun 6, 2024 at 5:41=E2=80=AFPM David Hildenbrand = wrote: > > On 06.06.24 11:38, Lance Yang wrote: > > On Thu, Jun 6, 2024 at 4:06=E2=80=AFPM David Hildenbrand wrote: > >> > >> On 06.06.24 10:01, David Hildenbrand wrote: > >>> On 06.06.24 05:55, Lance Yang wrote: > >>>> On Wed, Jun 5, 2024 at 10:28=E2=80=AFPM David Hildenbrand wrote: > >>>>> > >>>>> On 05.06.24 16:20, Lance Yang wrote: > >>>>>> Hi David, > >>>>>> > >>>>>> On Wed, Jun 5, 2024 at 8:46=E2=80=AFPM David Hildenbrand wrote: > >>>>>>> > >>>>>>> On 21.05.24 06:02, Lance Yang wrote: > >>>>>>>> In preparation for supporting try_to_unmap_one() to unmap PMD-ma= pped > >>>>>>>> folios, start the pagewalk first, then call split_huge_pmd_addre= ss() to > >>>>>>>> split the folio. > >>>>>>>> > >>>>>>>> Since TTU_SPLIT_HUGE_PMD will no longer perform immediately, we = might > >>>>>>>> encounter a PMD-mapped THP missing the mlock in the VM_LOCKED ra= nge during > >>>>>>>> the page walk. It=E2=80=99s probably necessary to mlock this THP= to prevent it from > >>>>>>>> being picked up during page reclaim. > >>>>>>>> > >>>>>>>> Suggested-by: David Hildenbrand > >>>>>>>> Suggested-by: Baolin Wang > >>>>>>>> Signed-off-by: Lance Yang > >>>>>>>> --- > >>>>>>> > >>>>>>> [...] again, sorry for the late review. > >>>>>> > >>>>>> No worries at all, thanks for taking time to review! > >>>>>> > >>>>>>> > >>>>>>>> diff --git a/mm/rmap.c b/mm/rmap.c > >>>>>>>> index ddffa30c79fb..08a93347f283 100644 > >>>>>>>> --- a/mm/rmap.c > >>>>>>>> +++ b/mm/rmap.c > >>>>>>>> @@ -1640,9 +1640,6 @@ static bool try_to_unmap_one(struct folio = *folio, struct vm_area_struct *vma, > >>>>>>>> if (flags & TTU_SYNC) > >>>>>>>> pvmw.flags =3D PVMW_SYNC; > >>>>>>>> > >>>>>>>> - if (flags & TTU_SPLIT_HUGE_PMD) > >>>>>>>> - split_huge_pmd_address(vma, address, false, folio)= ; > >>>>>>>> - > >>>>>>>> /* > >>>>>>>> * For THP, we have to assume the worse case ie pmd fo= r invalidation. > >>>>>>>> * For hugetlb, it could be much worse if we need to d= o pud > >>>>>>>> @@ -1668,20 +1665,35 @@ static bool try_to_unmap_one(struct foli= o *folio, struct vm_area_struct *vma, > >>>>>>>> mmu_notifier_invalidate_range_start(&range); > >>>>>>>> > >>>>>>>> while (page_vma_mapped_walk(&pvmw)) { > >>>>>>>> - /* Unexpected PMD-mapped THP? */ > >>>>>>>> - VM_BUG_ON_FOLIO(!pvmw.pte, folio); > >>>>>>>> - > >>>>>>>> /* > >>>>>>>> * If the folio is in an mlock()d vma, we must= not swap it out. > >>>>>>>> */ > >>>>>>>> if (!(flags & TTU_IGNORE_MLOCK) && > >>>>>>>> (vma->vm_flags & VM_LOCKED)) { > >>>>>>>> /* Restore the mlock which got missed = */ > >>>>>>>> - if (!folio_test_large(folio)) > >>>>>>>> + if (!folio_test_large(folio) || > >>>>>>>> + (!pvmw.pte && (flags & TTU_SPLIT_HUGE_= PMD))) > >>>>>>>> mlock_vma_folio(folio, vma); > > > > Should we still keep the '!pvmw.pte' here? Something like: > > > > if (!folio_test_large(folio) || !pvmw.pte) > > mlock_vma_folio(folio, vma); > > I was wondering the same the whole time ... > > > > > We can mlock the THP to prevent it from being picked up during page rec= laim. > > > > David, I=E2=80=99d like to hear your thoughts on this ;) > > but I think there is no need to for now, in the context of your patchset.= :) Agreed. Let's drop it for now :) Thanks a lot for your thoughts! Lance > > -- > Cheers, > > David / dhildenb >