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Wed, 12 Nov 2025 01:10:10 -0800 (PST) Date: Wed, 12 Nov 2025 09:10:09 +0000 From: Wei Yang To: Dev Jain Cc: Wei Yang , Lance Yang , linux-mm@kvack.org, baolin.wang@linux.alibaba.com, Liam.Howlett@oracle.com, ryan.roberts@arm.com, npache@redhat.com, baohua@kernel.org, akpm@linux-foundation.org, david@kernel.org, lorenzo.stoakes@oracle.com, ziy@nvidia.com Subject: Re: [PATCH] mm/khugepaged: continue to collapse on SCAN_PMD_NONE Message-ID: <20251112091009.5xewhutnvdaoxt5s@master> Reply-To: Wei Yang References: <20251112020031.25350-1-richard.weiyang@gmail.com> <06096f8b-4da0-4b5c-af3c-fd8871437c16@linux.dev> <20251112034008.ojwghkko74psu65v@master> <811bea18-30d0-446f-8840-d99698a6a9ba@arm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <811bea18-30d0-446f-8840-d99698a6a9ba@arm.com> User-Agent: NeoMutt/20170113 (1.7.2) X-Rspam-User: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: C1D3FC0004 X-Stat-Signature: 1hday5p7ybr5c9o5apidwzzdz5rymuza X-HE-Tag: 1762938612-963396 X-HE-Meta: U2FsdGVkX18mp5vAPboW4S39NHQ7PaDT5qYcVjDlZAnLt62mUn+xqXBMRjn8Djw0jM7SLYjXNGA5giTnatZElJHaeba+OYy9OQ87Xw+3wnvBclE+1d3RQiDZsLcqHqe8TasEaMBFwIGf9wSP//5wqp/ldPpOoFCsbOk4It+4V8/HvDDI7Of8HCa5EkMvgX3p07iNnsnGQbRxspeQlr+70eDUpKO3J0+DgE1S4ADNBIWZBJlXBUGgCAMDQ09kSogwRZHFymMIzL1BrbNE3rwfJ4UNcN4Yg4FeCSjr0UvLhzO45jiCR+vwJM7EL7h0CjfTKchDot+T5IULgrzCJwT8RhEZO5qQr9S7vpDWOs3eFZ0UoGi42w2z+i8bPnKdOyy5CtFSzyvwVSYqi7DY5flubSAJqV6NU3APN+l5v5CRsku2nLXWvQ7HynDzOTFL++9x6s5XwcRXcDZ3YCVFouFt39j6OKqrYBpfzhSuoLfv7WxuBh/2g544QYr20HV59eAixXtfH0kZh1UGVpi5Ea4Z790MkAq9biQqDZXC+BsXZip1BhkaEfZV6OMObm/FNaB/WsFnvyS9KGsbMs57lUeYhOjlfO/qfxuzM3BB//Ucu+3DUdwat3/h8X8msqVFFKwoCQ7JYXQEOsiTwvoSBCFsl/dLHw+C1Sk46LQdNsA6fPBGuzPC32BVUgamPygvFefRalBLRJUUaH/88aO8ky47I6d8IGL+BIcci2rKMI1+yTfbPN4PS79iq7J/lRbZTprmyZzOZ0ZoRwCH4KicAltAPOfFvrE8IXjAEXATDdOYPqg6XwKLYLz9SgOG8CeLCssQmfq7CRKc8lQuATv5UfiULrthA7uYioxzfLw6oSqSj6zLWIx5k86tdejyvdOX+l9g2U70PugZypuV8Jb+Mf1mX5e2PqiP42v5lRTK+qXJUl7dtSos1ij26cgc3wPuZD2JgUhEoff8iQO7ONTnyY4 0HD3wtfz 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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 09:28:34AM +0530, Dev Jain wrote: > >On 12/11/25 9:10 am, Wei Yang wrote: >> On Wed, Nov 12, 2025 at 10:37:06AM +0800, Lance Yang wrote: >> > >> > On 2025/11/12 10:00, Wei Yang wrote: >> > > SCAN_PMD_NONE means current pmd is empty, but we can still continue >> > > collapse next pmd range. >> > Right, bailing out of the whole MADV_COLLAPSE request just because >> > we encounter one empty PMD is too strict ... >> > >> > It makes sense to treat SCAN_PMD_NONE like the other whitelisted cases >> > (e.g., SCAN_PMD_NULL). >> > > Signed-off-by: Wei Yang >> > > --- >> > LGTM. >> > >> > Reviewed-by: Lance Yang >> > >> Thanks for the review. >> >> I'm currently evaluating the use of SCAN_NULL versus SCAN_NONE. It seems their >> usage in the current code is intermixed, and I'm questioning if there's a >> strong, practical reason to maintain a distinction between these two states. >> Should they be unified? > >There was some discussion about that in this thread: > >https://lore.kernel.org/all/v5ivpub6z2n2uyemlnxgbilzs52ep4lrary7lm7o6axxoneb75@yfacfl5rkzeh/ > >There are some cleanups mentioned in the thread which you can try if you want :) > Thanks, will take a look. -- Wei Yang Help you, Help me