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t=1781011213; bh=hVaej1augRXIFWuAG42FMnav00Af7NNV6S/ONanWmPo=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=Qn/TwL6pgtT8QYIE9U2tP7uwoTgnLZz5sBSxMK2focx9/jk2s/mZGV6jNIp6+u3yq 8wZgDhqklVGdn2RBWWSd4Kyr07glvsviq1pvtYGuGqkUUo4Iv2IXUHGiCXvXjNaGWk HJHR8oUDepujeZnV1PtcHCahmpScFH24ynMezpMPC702Q+vHoXKRwDi6W5MJkEoVbx c3FYIdYM1rMWUD4LkBqXFhBz8pLo+zvc89WIAk18ilxCNBTv0ywoHSoEqqsN/Or0sC EQ92l4d61A//VQFI9bTm+k5Yf12jzwdQbVXmZWlVYAoRNayPsgNkhQdIR3ur/C2Zvo SbrMwa6K0XmBg== Message-ID: Date: Tue, 9 Jun 2026 15:20:07 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable 1/1] mm/khugepaged: fix PMD collapse swap PTE accounting To: Lance Yang , akpm@linux-foundation.org Cc: ljs@kernel.org, ziy@nvidia.com, baolin.wang@linux.alibaba.com, liam@infradead.org, npache@redhat.com, ryan.roberts@arm.com, dev.jain@arm.com, baohua@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org References: <20260609120443.71864-1-lance.yang@linux.dev> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 4AD8F4001B X-Stat-Signature: ky1i63h8dnbw6ud5qzrk8stpe38b8h4y X-Rspamd-Server: rspam03 X-Rspam-User: X-HE-Tag: 1781011214-545878 X-HE-Meta: U2FsdGVkX186Trf4gW7JIOYIUz63CsR9bxwQlZ941curbU551iiZNVF/3gBy1R/a0Yi9DngSnapMTz1WlEvaIZBQMgjFx592g2NB6xE8MGBW+8gqzsyQPSj/fnF7E/EmbysCIDAyGtx0BX6Y9zm2XqVmeQ6ry/SrHMPHg62QiX2L1uWlSb9e6OnqQdgtxy/fdly+DZol7Ke38G2Vu1YOAR6uLsuop+wDiEQsArFv7pklev42FP8/Sc9fB8LNx4/X+5XD/uV7clUvvv84niNyJUjQ4aQMTNd1UdlqoVSczUw9Nnyw5jT4mUlVmunApOxG9Q/pg2O8MWJXRhj9Z81PcANL7hpFl2IsE1+iDaBsaeLLMhTEOovtthP5KiHhIup38VaC7iXFr/iMi5dvx9TtE1PJ2x3rl0k/A+U6Uwr7t5W2/PjXXYBsOLEJ4viSgzMfD1HHJ50tExz15D5h4lONiwHdfgZlv8mr9uqg7AORmofEjfLaLM+pSXdFhQ8w8vSoc0uQuLHxoe3JmzX33vF8LOr2lMevkXrTF8vdRR2TWGH1hiiNOJwgPL1R75EUFelQwtOpVIG62g0OZx8mOj0++ArUd0HMGeqRcceRk6Z+a9oWkAr5ox06Q8SwkqEBmcMswHCwYmBrbSEO6oCyjajxPGOzVmxVzHdAiHvBzpeQIGA6HYXJ2vnXwxfto1BwcZKV2g8JIl6PQKeVVqRX+hcqDt/DvqlpeVa6FwaU5p7WciE5F5k07f5nW5Hmoob+3uNxXQOI1t/SDPb7mHA3Q4YE2kzRTEa42Bd6fkViR7dnoRsCC8qFdsSBlVShEyFQhpb2NyNySni8wKS8Mbh0C6eFJB6+Z9vz3exQus/ey6VxBWX7hl9aAQvDzPge+naKIXVeRboGZCncrZjOP3YH/hN1uyS+J6tf0vqAkchlcW2LVNx3XtwnK+CBQbCPK7PKt3DVnm3ayjCUCebRfgs3lRm dL9hzTXg B5ij5CWUJcmkAHyS/UOO7LWjzlWjaOxcJ0nCr+S7Wx4PI1geFHrAVuDUrk8KtPpu7vbEwsL1YycUypZTubAIeGUm1+xqi76FzySYJnln3H3t8NsFKwKa2lqxlXUIrF+5be2MPpcgANZWzH0lBqhH7JtkAcBAkePRpDBfOE00/owE6R7JedyXHw8nfPGjMdgTsy1OtNIXRS0p+4ZtXodJ4xCWMF7qx+kPqAPDvyXzKY6NPHcNdFJxas+djKXn2nBo9jWcJ Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 6/9/26 14:04, Lance Yang wrote: > From: Lance Yang > > mthp_collapse() uses mthp_present_ptes to decide whether a range has > enough occupied PTEs to try collapse. Swap PTEs accepted by > collapse_scan_pmd() are counted in unmapped, but are not represented in > mthp_present_ptes. > > When lower orders are enabled, collapse_scan_pmd() relaxes max_ptes_none > so the scan can cover the whole PMD and build the bitmap. mthp_collapse() > then checks the PMD-order candidate using the bitmap. > > With max_ptes_none set to 0, a range with 511 present PTEs and one swap > PTE no longer reaches collapse_huge_page(), even though PMD collapse can > handle swap PTEs up to max_ptes_swap. > > Account unmapped PTEs only for PMD order. PMD collapse supports swap PTEs > through max_ptes_swap, while lower-order mTHP collapse does not currently > support non-present PTEs. Keep non-present PTEs out of the lower-order > eligibility check. > > Signed-off-by: Lance Yang > --- > Sent separately, as discussed in [1], to spell out the PMD-order swap PTE > case. Patch [2] is still only in mm-unstable, so no Fixes: tag. Right, probably we just want to add the Fixes: tag once Andrew moves the series to mm-stable? -- Cheers, David