From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-172.mta0.migadu.com (out-172.mta0.migadu.com [91.218.175.172]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id BC88836DA18 for ; Mon, 8 Jun 2026 07:14:19 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780902861; cv=none; b=VWrxEcAptPfO5pCLVjW7maTHxQeUfFUd0sohy2oXEXbpDGDncAixhVzn0opDkFICjybVl0mS+eTwYC6HNo8BbKvF2ivl8p8lvho/tolYtRV98hN/S7lQswDjjbrhNv2/T8U3tBr+2iEx3T+RIJPpK/H8BrGGpGsi7PapZlgv9E0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1780902861; c=relaxed/simple; bh=VA+9r/z3n+RbhWNhQjtlm5cjRKLYAfjlBGhasnng8WE=; h=From:To:Cc:Subject:Date:Message-Id:In-Reply-To:References: MIME-Version:Content-Type; b=RFQ+UNhTFGcpX+GvB/KdJBXy8NNjvYqHPxRMqI2qcdprYYhETW7kkg7saOmFz5KZ01xM3vjEJsxwztGz0z6KOEya0GD0ZNfOjjGj4oXKzihAv6mUJ6juS0JYLgFo6hGJV8iZrnYyMo/Ocl1BPE48YohOrZWvPT0ylthf1QuRi+Q= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=rHBdi2+z; arc=none smtp.client-ip=91.218.175.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="rHBdi2+z" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. 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> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT 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