From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 1E298F507 for ; Tue, 16 Sep 2025 00:11:13 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757981474; cv=none; b=ptuKSSjEFjCOVtYmKiUZ3AUiiXlaYzDHgcEyADPsRxs6WNrGXBp/6lL0k17SFO69X+lz59mIArJuRy163CmrBr/4CjsctWLR6KEV9bPgUyYI9OHAwUKCazaqWn7c1dC5zxF4DpadAGCS3W6ZmBsr5JFNBcKfX6StB4BFgDXaKSE= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1757981474; c=relaxed/simple; bh=fQf0ppc42EwsOf0ekWpZyi02hc7MO+o0unxS4+mjbmQ=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=drF7CPibckmW2ngEKGb3M/wwb9/A5kE7E3pncgbRh7NyhgkARKjNxzZretPY8jLSxoVxuhroyVUg+2LIwW26+QR3DUH6HpPC03wjPVljGk3pEi9XtjylrkWZZQYmDZH/s7nQ3Skq+Q91p3QzH9fm2ZCu6vgbFX2NM8FmrmTQyIU= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=bfrvjN6A; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="bfrvjN6A" Received: by smtp.kernel.org (Postfix) with ESMTPSA id D5625C4CEF5; Tue, 16 Sep 2025 00:11:12 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1757981473; bh=fQf0ppc42EwsOf0ekWpZyi02hc7MO+o0unxS4+mjbmQ=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=bfrvjN6As3FbUsPhLt9BCR9kK5UpprOa4pIBTdb4pS8bHCS6JXgKAEY41LwWtgB46 tvMb718/Mk96EUkT91bK54C8a3Jq+5PnN7ZGUwl8SQeDE8RTaK29+cpHVbPxbDsZk5 QOtoOJH/EW+xxZgvSjoejTWo3UQRemd8Vk/oKUH8= Date: Mon, 15 Sep 2025 17:11:12 -0700 From: Andrew Morton To: Suren Baghdasaryan Cc: kent.overstreet@linux.dev, vbabka@suse.cz, hannes@cmpxchg.org, usamaarif642@gmail.com, rientjes@google.com, roman.gushchin@linux.dev, harry.yoo@oracle.com, shakeel.butt@linux.dev, 00107082@163.com, pyyjason@gmail.com, pasha.tatashin@soleen.com, souravpanda@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v2 1/1] alloc_tag: mark inaccurate allocation counters in /proc/allocinfo output Message-Id: <20250915171112.f71a7606a7f9fd3054662bed@linux-foundation.org> In-Reply-To: <20250915230224.4115531-1-surenb@google.com> References: <20250915230224.4115531-1-surenb@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) 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=US-ASCII Content-Transfer-Encoding: 7bit On Mon, 15 Sep 2025 16:02:24 -0700 Suren Baghdasaryan wrote: > While rare, memory allocation profiling can contain inaccurate counters > if slab object extension vector allocation fails. That allocation might > succeed later but prior to that, slab allocations that would have used > that object extension vector will not be accounted for. To indicate > incorrect counters, "accurate:no" marker is appended to the call site > line in the /proc/allocinfo output. > Bump up /proc/allocinfo version to reflect the change in the file format > and update documentation. > > Example output with invalid counters: > allocinfo - version: 2.0 > 0 0 arch/x86/kernel/kdebugfs.c:105 func:create_setup_data_nodes > 0 0 arch/x86/kernel/alternative.c:2090 func:alternatives_smp_module_add > 0 0 arch/x86/kernel/alternative.c:127 func:__its_alloc accurate:no > 0 0 arch/x86/kernel/fpu/regset.c:160 func:xstateregs_set > 0 0 arch/x86/kernel/fpu/xstate.c:1590 func:fpstate_realloc > 0 0 arch/x86/kernel/cpu/aperfmperf.c:379 func:arch_enable_hybrid_capacity_scale > 0 0 arch/x86/kernel/cpu/amd_cache_disable.c:258 func:init_amd_l3_attrs > 49152 48 arch/x86/kernel/cpu/mce/core.c:2709 func:mce_device_create accurate:no > 32768 1 arch/x86/kernel/cpu/mce/genpool.c:132 func:mce_gen_pool_create > 0 0 arch/x86/kernel/cpu/mce/amd.c:1341 func:mce_threshold_create_device > > ... > > --- a/Documentation/filesystems/proc.rst > +++ b/Documentation/filesystems/proc.rst > @@ -1009,6 +1009,10 @@ number, module (if originates from a loadable module) and the function calling > the allocation. The number of bytes allocated and number of calls at each > location are reported. The first line indicates the version of the file, the > second line is the header listing fields in the file. > +If file version is 2.0 or higher then each line may contain additional > +: pairs representing extra information about the call site. > +For example if the counters are not accurate, the line will be appended with > +"accurate:no" pair. Perhaps we can tell people what accurate:no actually means. It is a rather disturbing thing to see! How worried should our users be about it?