From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id EFCAC3DDAF0 for ; Mon, 6 Jul 2026 14:38:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783348727; cv=none; b=rKGWDLvZb16/UpLSRhZd6lbublKmukbRmtRv+7tmX+BFBfxPqtPVwcKpRMpIeYRe3xcDP0zzADbK/C08ilB1IWF4e8/6xu4eIK+6ikuFK48mPm9vsT0O21lBqCQq8NmBmEa2jF4tc3MKjvdaLJuEwbrvI4vF2lipDBcdNCaPlFs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783348727; c=relaxed/simple; bh=e6pRSvllnF+KJoD7AeGJIAbvHAR7f92Wq2wyQCokt6A=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=jg3EeQNLxpPsgf9BRmn00XHjW7HMSKqB1eQq6Ov45RJK7Yoyrbv/ZioOpmGJulSFcqOannMmi7JM1S3ZLkH+xAARkQ492veWwzExCfv/k4u0RYP8/j3NNIgiYZumju8JLBJx0bbQkKJxjVKxCWEOsoI+I/giJA3PMD4lXCOJuhU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b=DQxJ7Zn8; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=arm.com header.i=@arm.com header.b="DQxJ7Zn8" Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id E7A3D1BB2; Mon, 6 Jul 2026 07:38:40 -0700 (PDT) Received: from [192.168.178.6] (usa-sjc-mx-foss1.foss.arm.com [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 823143F905; Mon, 6 Jul 2026 07:38:42 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=arm.com; s=foss; t=1783348725; bh=e6pRSvllnF+KJoD7AeGJIAbvHAR7f92Wq2wyQCokt6A=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=DQxJ7Zn8NVujF36hrCZAchQc6scBPbHGyQADUInyJqhSYTOVvF47iPlPuP+1Kgzdc YFOkiQ590ZY07BZIw+WUpgkIzA1E23Lg9D5zz9jlN43TZuoCyPbULEEgjyOWAcRuYf HMuW7V+Jd/3Rq8obUYCHWBRQ1StN5QNBYiin0XNE= Message-ID: <9476c607-92bd-4f98-b9a0-c9ca559c9d91@arm.com> Date: Mon, 6 Jul 2026 16:38:36 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: kmemleak: sched_domain_shared leaked on asymmetric-capacity + SCHED_CACHE To: K Prateek Nayak , Breno Leitao Cc: Andrea Righi , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Steven Rostedt , Ben Segall , Mel Gorman , Valentin Schneider , Christian Loehle , Phil Auld , Koba Ko , Felix Abecassis , Balbir Singh , Joel Fernandes , Shrikanth Hegde , linux-kernel@vger.kernel.org References: <20260509180955.1840064-1-arighi@nvidia.com> <20260509180955.1840064-3-arighi@nvidia.com> <73685ae1-6d90-4799-a1d7-08a1fcf24b8b@amd.com> <73697ae3-f826-4b0e-be05-446976223822@amd.com> From: Dietmar Eggemann Content-Language: en-GB In-Reply-To: <73697ae3-f826-4b0e-be05-446976223822@amd.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Hi Breno & Prateek, On 04.07.26 08:16, K Prateek Nayak wrote: > Hello Breno, > > On 7/3/2026 9:49 PM, Breno Leitao wrote: >> Hello Prateek, >> >> On Fri, Jul 03, 2026 at 04:05:59PM +0530, K Prateek Nayak wrote: >>> On 7/3/2026 3:52 PM, Breno Leitao wrote: >>>> On current linux-next (CONFIG_SCHED_CACHE=y) we hit a kmemleak on an >>>> arm64 box with asymmetric CPU capacity, triggered by a cpuset-driven >>>> sched-domain rebuild: >>>> >>>> kmemleak: unreferenced object 0xffff000100c95e80 (size 32): >>>> comm "kworker/22:1", pid 407, jiffies 4294669077 >>>> hex dump (first 32 bytes): >>>> 48 00 00 00 48 00 00 00 00 00 00 00 20 00 00 00 H...H....... ... >>>> backtrace (crc ec5d7053): >>>> __kmalloc_cache_node_noprof >>>> build_sched_domains >>>> partition_sched_domains >>>> rebuild_sched_domains_locked >>>> rebuild_sched_domains >>>> process_scheduled_works >>>> kthread >>>> ret_from_fork >>>> kmemleak: 1 new suspected memory leaks >>>> >>>> The leaked object is a struct sched_domain_shared (32 bytes with >>>> CONFIG_SCHED_CACHE) allocated in __sds_alloc(), inlined into >>>> build_sched_domains() >>>> >>>> Is this a known issue? >>> >>> It is theoretically possible but there is a defensive WARN_ON() >>> in topology code that you should have hit first. Do you see any >>> other warning? >>> >>> If it is not too much trouble, could you add "sched_verbose" >>> to your kernel cmdline (or do >>> echo Y > /sys/kernel/debug/sched/verbose) and redo this cpuset >>> that leaks the data and share the dmesg. It should give some clue >>> what the topology looks like that causes this. >> >> Sure, does this one help: > > Unfortunately no! This doesn't give the span and capacity > information so I cannot really tell what kind of topology > actually triggers this. I'm trying to recreate this on Arm64 qemu with dtb file to get the asymmetric CPU capacities (emulating Pixel6): $ cat /sys/devices/system/cpu/cpu*/cpu_capacity 160 160 160 160 498 498 1024 1024 I'm on linux_next master: eb8711ece2c - (HEAD -> linux-next, tag: next-20260702, linux-next/master) so it has: 9e005ed21152 - sched/topology: Allow multiple domains to claim sched_domain_shared (2026-05-19 K Prateek Nayak) $ cat /sys/kernel/debug/sched/domains/cpu0/domain0/{name,flags} MC SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING 8 CPUs flat: $ cat /proc/schedstat | grep "^c\|^d" | awk '{ print $1 " " $2 " " $3}' cpu0 0 0 domain0 MC ff cpu1 0 0 domain0 MC ff cpu2 0 0 domain0 MC ff cpu3 0 0 domain0 MC ff cpu4 0 0 domain0 MC ff cpu5 0 0 domain0 MC ff cpu6 0 0 domain0 MC ff cpu7 0 0 domain0 MC ff > Ideally, you enable verbose logging, do the cpuset operation > that leaks the object, and then save the demesg after which > will have a complete topology for all CPUs there including > their capacities and we can piece together a qemu environment > to debug where it all went wrong. +1 $ cat /proc/cmdline ... sched_verbose=1 What exactly is this cpuset operation forcing a sched domain rebuild? I'm trying a split into 2 exclusive cpusets {0,2,4,6} and {1,3,5,7} to get 2 asymmetric CPU capacity islands. ... [ 95.747359] root domain span: 1,3,5,7 [ 95.747760] root domain span: 0,2,4,6 [ 95.747771] _sched_cache_active_set: enabling cache aware scheduling [ 95.747788] rd 1,3,5,7: Checking EAS: frequency-invariant load tracking not yet supported ... $ cat /sys/kernel/debug/sched/domains/cpu0/domain0/{name,flags} MC SD_BALANCE_NEWIDLE SD_BALANCE_EXEC SD_BALANCE_FORK SD_WAKE_AFFINE SD_ASYM_CPUCAPACITY SD_ASYM_CPUCAPACITY_FULL SD_SHARE_LLC SD_PREFER_SIBLING $ cat /proc/schedstat | grep "^c\|^d" | awk '{ print $1 " " $2 " " $3}' cpu0 0 0 domain0 MC 55 cpu1 0 0 domain0 MC aa cpu2 0 0 domain0 MC 55 cpu3 0 0 domain0 MC aa cpu4 0 0 domain0 MC 55 cpu5 0 0 domain0 MC aa cpu6 0 0 domain0 MC 55 cpu7 0 0 domain0 MC aa But this hasn't triggered kmemleak so far. That said, it triggered once (~600s uptime) but w/o any cpuset operation? Never happened again since then :-( [...] > Is this the defualt topology before the cpuset? Because > min_interval of 8 means there are 8 cPUs in the span and > you have 8 CPUs in your machine so there seems to be a > single root partition when you captured this. +1 > Also does your dmesg have any warnings from topology.c? > > The only way I can see this triggering is there is a single > cpu SD_SHARE_LLC at top which claims all the sd->shared and > then you get a SD_ASYM_CPUCAPACITY_FULL on top which too > tries to claim a sd->shared but all are already gone. ? > Afaict, all CPUs in your system are on single LLC and you > can't SD_ASYM_CPUCAPACITY_FULL without having more than one > capacity in the span so I'm at a loss currently as to how > this reference gets dropped without being freed. $ cat /sys/devices/system/cpu/cpu*/cpu_capacity should tell. Another thing: does your system enable 'cache aware scheduling', i.e. do you not see: pr_info("%s: cache aware scheduling not supported on this platform\n", __func__);