From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-182.mta0.migadu.com (out-182.mta0.migadu.com [91.218.175.182]) (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 269572BDC23 for ; Fri, 13 Mar 2026 06:14:49 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=91.218.175.182 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773382492; cv=none; b=rDwVYW4NxarwZAZUhmeQ8errxGsmrYmcL1uOrIg66k6eKzP0hxhVA9V1cgskT+5pIuWQ8c64bipBqIpmMt04w5wCwByMvmH7jcFrz35ju2SsPnDGzODd8c08O1+Th14ZzKOF8civSE+0TrjTc8cwuPy/gFQqSUkQpZl9rQMgenA= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1773382492; c=relaxed/simple; bh=TxGCibyeKxKkTZWMmZEfTZ0Hk4cAVCjiVlBujR9CsAE=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=UP8PMviotl+IkcuMTbNxxyVBfsDnxO3j1keAdA00T+FFap1DFJOkLayofivU6Y/vjebssdtN8GLQ8bGYyXgkAJa45tEKHm9h5S5FMojnSZwHnzPHSMVSpMmjgUs436UdJgBPX8PtYqhVeUCjZLv/UIV+Sk0XcZFlfjcRK1wzugY= 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=uAFdS55K; arc=none smtp.client-ip=91.218.175.182 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="uAFdS55K" Message-ID: DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1773382487; 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=PTOLkQVeVRERnDaN2DY/VOKpnGSBVqeHDpUKHThv08w=; b=uAFdS55KeRCswjq75c2XPetMdLBZz02PMZndCgnGus7RcpkYRA42aQWgO5+73Z48XT+QNy goFei+e4hH/qigznuSXoYYNL6W3QKa4gIO+u47sTlzngo4sHrD4fcv3iyLO3QODXGRMxgX lvTyN830y+LMTKxFJU96X0nsOAQ57sI= Date: Thu, 12 Mar 2026 23:14:36 -0700 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Subject: Re: [PATCH v2] mm/mempolicy: track page allocations per mempolicy To: "Huang, Ying" Cc: "Vlastimil Babka (SUSE)" , linux-mm@kvack.org, akpm@linux-foundation.org, mhocko@suse.com, apopple@nvidia.com, axelrasmussen@google.com, byungchul@sk.com, cgroups@vger.kernel.org, david@kernel.org, eperezma@redhat.com, gourry@gourry.net, jasowang@redhat.com, hannes@cmpxchg.org, joshua.hahnjy@gmail.com, Liam.Howlett@oracle.com, linux-kernel@vger.kernel.org, lorenzo.stoakes@oracle.com, matthew.brost@intel.com, mst@redhat.com, rppt@kernel.org, muchun.song@linux.dev, zhengqi.arch@bytedance.com, rakie.kim@sk.com, roman.gushchin@linux.dev, shakeel.butt@linux.dev, surenb@google.com, virtualization@lists.linux.dev, weixugc@google.com, xuanzhuo@linux.alibaba.com, yuanchu@google.com, ziy@nvidia.com, kernel-team@meta.com References: <20260307045520.247998-1-jp.kobryn@linux.dev> <3a42463b-9ddd-4d64-b64c-6c2e6e4fc75d@kernel.org> <343bbd5b-67a0-46c4-8ec4-69158bf26b3f@linux.dev> <874imkpba1.fsf@DESKTOP-5N7EMDA> Content-Language: en-US X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. From: "JP Kobryn (Meta)" In-Reply-To: <874imkpba1.fsf@DESKTOP-5N7EMDA> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Migadu-Flow: FLOW_OUT On 3/12/26 10:07 PM, Huang, Ying wrote: > "JP Kobryn (Meta)" writes: > >> On 3/12/26 6:40 AM, Vlastimil Babka (SUSE) wrote: >>> On 3/7/26 05:55, JP Kobryn (Meta) wrote: >>>> When investigating pressure on a NUMA node, there is no straightforward way >>>> to determine which policies are driving allocations to it. >>>> >>>> Add per-policy page allocation counters as new node stat items. These >>>> counters track allocations to nodes and also whether the allocations were >>>> intentional or fallbacks. >>>> >>>> The new stats follow the existing numa hit/miss/foreign style and have the >>>> following meanings: >>>> >>>> hit >>>> - for BIND and PREFERRED_MANY, allocation succeeded on node in nodemask >>>> - for other policies, allocation succeeded on intended node >>>> - counted on the node of the allocation >>>> miss >>>> - allocation intended for other node, but happened on this one >>>> - counted on other node >>>> foreign >>>> - allocation intended on this node, but happened on other node >>>> - counted on this node >>>> >>>> Counters are exposed per-memcg, per-node in memory.numa_stat and globally >>>> in /proc/vmstat. >>>> >>>> Signed-off-by: JP Kobryn (Meta) >>> I think I've been on of the folks on previous versions arguing >>> against the >>> many counters, and one of the arguments was it they can't tell the full >>> story anyway (compared to e.g. tracing), but I don't think adding even more >>> counters is the right solution. Seems like a number of other people >>> responding to the thread are providing similar feedback. >>> For example I'm still not sure how it would help me if I knew the >>> hits/misses were due to a preferred vs preferred_many policy, or interleave >>> vs weithed interleave? >>> >> >> How about I change from per-policy hit/miss/foreign triplets to a single >> aggregated policy triplet (i.e. just 3 new counters which account for >> all policies)? They would follow the same hit/miss/foreign semantics >> already proposed (visible in quoted text above). This would still >> provide the otherwise missing signal of whether policy-driven >> allocations to a node are intentional or fallback. >> >> Note that I am also planning on moving the stats off of the memcg so the >> 3 new counters will be global per-node in response to similar feedback. > > Emm, what's the difference between these newly added counters and the > existing numa_hit/miss/foreign counters? The existing counters don't account for node masks in the policies that make use of them. An allocation can land on a node in the mask and still be considered a miss because it wasn't the preferred node.