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Wed, 12 Nov 2025 03:27:39 -0800 (PST) Date: Wed, 12 Nov 2025 11:27:39 +0000 From: Wei Yang To: "David Hildenbrand (Red Hat)" Cc: Wei Yang , akpm@linux-foundation.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, lance.yang@linux.dev, linux-mm@kvack.org Subject: Re: [PATCH] mm/khugepaged: continue to collapse on SCAN_PMD_NONE Message-ID: <20251112112739.ovfkj6zy7kqcervv@master> Reply-To: Wei Yang References: <20251112020031.25350-1-richard.weiyang@gmail.com> <04e8e813-b43b-423e-8ad9-fb13ac953055@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: NeoMutt/20170113 (1.7.2) X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: C81761C0005 X-Stat-Signature: qiwfdu69qmbbszre5agfm9zmabxddys7 X-Rspam-User: X-HE-Tag: 1762946861-588491 X-HE-Meta: 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 YwZ90auN 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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, Nov 12, 2025 at 10:51:43AM +0100, David Hildenbrand (Red Hat) wrote: >On 12.11.25 10:51, David Hildenbrand (Red Hat) wrote: >> On 12.11.25 03:00, Wei Yang wrote: >> > SCAN_PMD_NONE means current pmd is empty, but we can still continue >> > collapse next pmd range. >> > >> > Signed-off-by: Wei Yang >> > --- >> > mm/khugepaged.c | 1 + >> > 1 file changed, 1 insertion(+) >> > >> > diff --git a/mm/khugepaged.c b/mm/khugepaged.c >> > index 7e8cb181d5bd..4c2217076ad3 100644 >> > --- a/mm/khugepaged.c >> > +++ b/mm/khugepaged.c >> > @@ -2835,6 +2835,7 @@ int madvise_collapse(struct vm_area_struct *vma, unsigned long start, >> > goto handle_result; >> > /* Whitelisted set of results where continuing OK */ >> > case SCAN_PMD_NULL: >> > + case SCAN_PMD_NONE: >> > case SCAN_PTE_NON_PRESENT: >> > case SCAN_PTE_UFFD_WP: >> > case SCAN_LACK_REFERENCED_PAGE: >> >> Looks ok to me. >> >> I am really confused about PMD_NONE vs. PMD_NULL. >> >> Is my understanding correct, hat with your patch we can just merge both >> into a single NO_PMD_TABLE or sth. like that? > >NO_PTE_TABLE, actually > I am thinking about this too. If no other objections, I will prepare a v2 with this. BTW, you prefer merge them directly, or merge on top of this change? >-- >Cheers > >David -- Wei Yang Help you, Help me