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 VUWN18xK 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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 29 May 2025, at 22:21, Baolin Wang wrote: > On 2025/5/30 10:04, Zi Yan wrote: >> On 29 May 2025, at 21:51, Baolin Wang wrote: >> >>> On 2025/5/29 23:10, Zi Yan wrote: >>>> On 29 May 2025, at 4:23, Baolin Wang wrote: >>>> >>>>> The MADV_COLLAPSE will ignore the system-wide Anon THP sysfs settings= , which >>>>> means that even though we have disabled the Anon THP configuration, M= ADV_COLLAPSE >>>>> will still attempt to collapse into a Anon THP. This violates the rul= e we have >>>>> agreed upon: never means never. >>>>> >>>>> To address this issue, should check whether the Anon THP configuratio= n is disabled >>>>> in thp_vma_allowable_orders(), even when the TVA_ENFORCE_SYSFS flag i= s set. >>>>> >>>>> Signed-off-by: Baolin Wang >>>>> --- >>>>> include/linux/huge_mm.h | 23 +++++++++++++++++++---- >>>>> 1 file changed, 19 insertions(+), 4 deletions(-) >>>>> >>>>> diff --git a/include/linux/huge_mm.h b/include/linux/huge_mm.h >>>>> index 2f190c90192d..199ddc9f04a1 100644 >>>>> --- a/include/linux/huge_mm.h >>>>> +++ b/include/linux/huge_mm.h >>>>> @@ -287,20 +287,35 @@ unsigned long thp_vma_allowable_orders(struct v= m_area_struct *vma, >>>>> unsigned long orders) >>>>> { >>>>> /* Optimization to check if required orders are enabled early. */ >>>>> - if ((tva_flags & TVA_ENFORCE_SYSFS) && vma_is_anonymous(vma)) { >>>>> - unsigned long mask =3D READ_ONCE(huge_anon_orders_always); >>>>> + if (vma_is_anonymous(vma)) { >>>>> + unsigned long always =3D READ_ONCE(huge_anon_orders_always); >>>>> + unsigned long madvise =3D READ_ONCE(huge_anon_orders_madvise); >>>>> + unsigned long inherit =3D READ_ONCE(huge_anon_orders_inherit); >>>>> + unsigned long mask =3D always | madvise; >>>>> + >>>>> + /* >>>>> + * If the system-wide THP/mTHP sysfs settings are disabled, >>>>> + * then we should never allow hugepages. >>>>> + */ >>>>> + if (!(mask & orders) && !(hugepage_global_enabled() && (inherit & = orders))) >>>> >>>> Can you explain the logic here? Is it equivalent to: >>>> 1. if THP is set to always, always_mask & orders =3D=3D 0, or >>>> 2. if THP if set to madvise, madvise_mask & order =3D=3D 0, or >>>> 3. if THP is set to inherit, inherit_mask & order =3D=3D 0? >>>> >>>> I cannot figure out why (always | madvise) & orders does not check >>>> THP enablement case, but inherit & orders checks hugepage_global_enabl= ed(). >>> >>> Sorry for not being clear. Let me try again: >>> >>> Now we can control per-sized mTHP through =E2=80=98huge_anon_orders_alw= ays=E2=80=99, so always does not need to rely on the check of hugepage_glob= al_enabled(). >>> >>> For madvise, referring to David's suggestion: =E2=80=9Callowing for col= lapsing in a VM without VM_HUGEPAGE in the "madvise" mode would be fine", s= o we can just check 'huge_anon_orders_madvise' without relying on hugepage_= global_enabled(). >> >> Got it. Setting always or madvise knob in per-size mTHP means user wants= to >> enable that size, so their orders are not limited by the global config. >> Setting inherit means user wants to follow the global config. >> Now it makes sense to me. I wonder if renaming inherit to inherit_global >> and huge_anon_orders_inherit to huge_anon_orders_inherit_global >> could make code more clear (We cannot change sysfs names, but changing >> kernel variable names should be fine?). > > The 'huge_anon_orders_inherit' is also a per-size mTHP interface. See the= doc: > " > Alternatively it is possible to specify that a given hugepage size > will inherit the top-level "enabled" value:: > > echo inherit >/sys/kernel/mm/transparent_hugepage/hugepages-kB/enabled > " > > The 'inherit' already implies that it is meant to inherit the top-level '= enabled' value, so I personally still prefer the variable name 'inherit', j= ust as we use it elsewhere. OK. No problem. > >>> In the case where hugepage_global_enabled() is enabled, we need to chec= k whether the 'inherit' has enabled the corresponding orders. >>> >>> In summary, the current strategy is: >>> >>> 1. If always & orders =3D=3D 0, and madvise & orders =3D=3D 0, and huge= page_global_enabled() =3D=3D false (global THP settings are not enabled), i= t means mTHP of the orders are prohibited from being used, then madvise_col= lapse() is forbidden. >>> >>> 2. If always & orders =3D=3D 0, and madvise & orders =3D=3D 0, and huge= page_global_enabled() =3D=3D true (global THP settings are enabled), and in= herit & orders =3D=3D 0, it means mTHP of the orders are still prohibited f= rom being used, and thus madvise_collapse() is not allowed. >> >> Putting the summary in the comment might be very helpful. WDYT? > > Sure. will do. Thanks. > >> Otherwise, the patch looks good to me. Thanks. >> >> Reviewed-by: Zi Yan > > Thanks. Best Regards, Yan, Zi