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DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1780902846; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=t3DfQ5vwWCckZGkA87/DSfdL+GVPQKWQGnRbRGwtS94=; b=rHBdi2+zew9CwX9JzM5CIi0bAAjqQd2xi3+2yfyULKQaqBBpfay7Z6/nK5Y6px4dq86NAt H3KNQz9QRnC3ymTmBRIrbdi3ShIKJibCXsKvCwwJdBfGnNZG9jvrXc3IQb6RkxXPpB7Xlm pdcWF/RCLj52b0xE2Pdn+dpnpyCMK8w= From: Lance Yang To: npache@redhat.com Cc: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org, aarcange@redhat.com, akpm@linux-foundation.org, anshuman.khandual@arm.com, apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, catalin.marinas@arm.com, cl@gentwo.org, corbet@lwn.net, dave.hansen@linux.intel.com, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, hannes@cmpxchg.org, hughd@google.com, jack@suse.cz, jackmanb@google.com, jannh@google.com, jglisse@google.com, joshua.hahnjy@gmail.com, kas@kernel.org, lance.yang@linux.dev, liam@infradead.org, ljs@kernel.org, mathieu.desnoyers@efficios.com, matthew.brost@intel.com, mhiramat@kernel.org, mhocko@suse.com, peterx@redhat.com, pfalcato@suse.de, rakie.kim@sk.com, raquini@redhat.com, rdunlap@infradead.org, richard.weiyang@gmail.com, rientjes@google.com, rostedt@goodmis.org, rppt@kernel.org, ryan.roberts@arm.com, shivankg@amd.com, sunnanyong@huawei.com, surenb@google.com, thomas.hellstrom@linux.intel.com, tiwai@suse.de, usamaarif642@gmail.com, vbabka@suse.cz, vishal.moola@gmail.com, wangkefeng.wang@huawei.com, will@kernel.org, willy@infradead.org, yang@os.amperecomputing.com, ying.huang@linux.alibaba.com, ziy@nvidia.com, zokeefe@google.com Subject: Re: [PATCH mm-unstable v19 08/14] mm/khugepaged: add per-order mTHP collapse failure statistics Date: Mon, 8 Jun 2026 15:13:52 +0800 Message-Id: <20260608071352.77428-1-lance.yang@linux.dev> In-Reply-To: <20260605161422.213817-9-npache@redhat.com> References: <20260605161422.213817-9-npache@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT X-Rspamd-Server: rspam07 X-Rspam-User: X-Stat-Signature: 8gaktrdp9aniqksh6i7mp9mhzk5haq3y X-Rspamd-Queue-Id: A27EAC0008 X-HE-Tag: 1780902849-657853 X-HE-Meta: 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 SSYVAzhV VGm083Ax5O/bi2riM2KD7X4BikvYJKQVyXo+uYkvQ3PDe573lEMRbUi67SMPEPTlbBLksoL5Ed2TAnAhpeBWuOSRL1MXHn5+utRese06uxjo3+TSkrGXx3NOiRG6kPgyX8Fqb98yqPsKGNdEor3pCyj6upM3f3iuHNA7YbTbHJmOIWEv/iXz9RL/F46iYpJv6d+ZriIlkt0HWDsGxaI/Htn1TCKCKee5Qb4Mf2yfLA7acL2X3AbwMZDrHiPR2jDqeHRJrjdhdxZCRqUvNCXPD3m6JEZmU9rvlMmTr+eI012I6NMAPdCdjwE5Gu9oVS9SbIxRWuRbjXbrFTng= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, Jun 05, 2026 at 10:14:15AM -0600, Nico Pache wrote: >Add three new mTHP statistics to track collapse failures for different >orders when encountering swap PTEs, excessive none PTEs, and shared PTEs: > >- collapse_exceed_swap_pte: Increment when mTHP collapse fails due to > encountering a swap PTE. > >- collapse_exceed_none_pte: Counts when mTHP collapse fails due to > exceeding the none PTE threshold for the given order > >- collapse_exceed_shared_pte: Counts when mTHP collapse fails due to > encountering a shared PTE. > >These statistics complement the existing THP_SCAN_EXCEED_* events by >providing per-order granularity for mTHP collapse attempts. The stats are >exposed via sysfs under >`/sys/kernel/mm/transparent_hugepage/hugepages-*/stats/` for each >supported hugepage size. > >As we currently do not support collapsing mTHPs that contain a swap or >shared entry, those statistics keep track of how often we are >encountering failed mTHP collapses due to these restrictions. > >We will add support for mTHP collapse for anonymous pages next; lets also >track when this happens at the PMD level within the per-mTHP stats. > >Reviewed-by: Lorenzo Stoakes >Acked-by: David Hildenbrand (Arm) >Signed-off-by: Nico Pache >--- Reviewed-by: Lance Yang