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Thu, 11 Sep 2025 23:22:01 -0700 (PDT) MIME-Version: 1.0 References: <20250910024447.64788-1-laoar.shao@gmail.com> <20250910024447.64788-5-laoar.shao@gmail.com> In-Reply-To: From: Yafang Shao Date: Fri, 12 Sep 2025 14:21:25 +0800 X-Gm-Features: AS18NWDgNlviB90497XwhehyjdnC0mbss2uvTJ6B4snySt0rWu9vzBh6IpQFiW4 Message-ID: Subject: Re: [PATCH v7 mm-new 04/10] mm: thp: enable THP allocation exclusively through khugepaged To: Lance Yang Cc: akpm@linux-foundation.org, david@redhat.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, lorenzo.stoakes@oracle.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, hannes@cmpxchg.org, usamaarif642@gmail.com, gutierrez.asier@huawei-partners.com, willy@infradead.org, ast@kernel.org, daniel@iogearbox.net, andrii@kernel.org, ameryhung@gmail.com, rientjes@google.com, corbet@lwn.net, 21cnbao@gmail.com, shakeel.butt@linux.dev, bpf@vger.kernel.org, linux-mm@kvack.org, linux-doc@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Rspam-User: X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: C943680005 X-Stat-Signature: n7szjawzdzog5uxdzwdm4f1qqpqemou9 X-HE-Tag: 1757658122-564898 X-HE-Meta: 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 to+sJzLU 1awTQx8MOb2Ek7Bs5YmFVni5c7Uqs37z7wJs0p7fbqLkglFZ3uev4LU+ld8DxWmz3jrLRNlgoQoJsgcDAm5/irMqa1e9M8Dz12cqJUMmTDLVUF9+yPu2+mtOS1A1bHDliNc3kjmhudxmXPVgYRqmFGfQi+zDM2QONxwsDthgX6Cl9d4XSzvDHexzUba45hC/VdYSxaAdpy6K3FOMekHDPe45yYrTd9Ts1wzg+Q5LoIRChD1VkKSn53smOlZCLGITsVsWmkMbCBT768xFy6wCZHxL91UStLccSZJ9h1PoXcXo+zFD1F1MFs2OPgLhjRFiUW4gF5zERuUSxT+gnzgWfeUVMEp0QmxtHMGwOXVtwTqGN9iPbGHOo0uJh0cWXyM+b7O4EbvnOjZDSl/ukZgGr6vUCQa0fa24dR56aLQcV9rBPjFEdl1KGUoqJw+f9s2qo3ZTU 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, Sep 11, 2025 at 11:54=E2=80=AFPM Lance Yang = wrote: > > On Wed, Sep 10, 2025 at 11:00=E2=80=AFAM Yafang Shao wrote: > > > > Currently, THP allocation cannot be restricted to khugepaged alone whil= e > > being disabled in the page fault path. This limitation exists because > > disabling THP allocation during page faults also prevents the execution= of > > khugepaged_enter_vma() in that path. > > > > With the introduction of BPF, we can now implement THP policies based o= n > > different TVA types. This patch adjusts the logic to support this new > > capability. > > > > While we could also extend prtcl() to utilize this new policy, such a > > change would require a uAPI modification. > > > > Signed-off-by: Yafang Shao > > --- > > mm/huge_memory.c | 1 - > > mm/memory.c | 13 ++++++++----- > > 2 files changed, 8 insertions(+), 6 deletions(-) > > > > diff --git a/mm/huge_memory.c b/mm/huge_memory.c > > index 523153d21a41..1e9e7b32e2cf 100644 > > --- a/mm/huge_memory.c > > +++ b/mm/huge_memory.c > > @@ -1346,7 +1346,6 @@ vm_fault_t do_huge_pmd_anonymous_page(struct vm_f= ault *vmf) > > ret =3D vmf_anon_prepare(vmf); > > if (ret) > > return ret; > > - khugepaged_enter_vma(vma, vma->vm_flags); > > > > if (!(vmf->flags & FAULT_FLAG_WRITE) && > > !mm_forbids_zeropage(vma->vm_mm) && > > diff --git a/mm/memory.c b/mm/memory.c > > index d8819cac7930..d0609dc1e371 100644 > > --- a/mm/memory.c > > +++ b/mm/memory.c > > @@ -6289,11 +6289,14 @@ static vm_fault_t __handle_mm_fault(struct vm_a= rea_struct *vma, > > if (pud_trans_unstable(vmf.pud)) > > goto retry_pud; > > > > - if (pmd_none(*vmf.pmd) && > > - thp_vma_allowable_order(vma, vm_flags, TVA_PAGEFAULT, PMD_O= RDER)) { > > - ret =3D create_huge_pmd(&vmf); > > - if (!(ret & VM_FAULT_FALLBACK)) > > - return ret; > > + if (pmd_none(*vmf.pmd)) { > > + if (vma_is_anonymous(vma)) > > + khugepaged_enter_vma(vma, vm_flags); > > Hmm... I'm a bit confused about the different conditions for calling > khugepaged_enter_vma(). It's sometimes called for anonymous VMAs, other > times ONLY for non-anonymous, and sometimes unconditionally ;) Right, it is really confusing. > > Anyway, this isn't a blocker, just something I noticed. I might try to > simplify that down the road. please do it when you have a moment. > > Acked-by: Lance Yang Thanks for the review. --=20 Regards Yafang