From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-0.5 required=3.0 tests=DATE_IN_PAST_12_24, DKIMWL_WL_HIGH,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 74F17C2D0EC for ; Mon, 30 Mar 2020 06:27:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4AA5920732 for ; Mon, 30 Mar 2020 06:27:32 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585549652; bh=6IiawiuXQLOjYANKVy5JYWeqTQaiqOyWrx4qr3Digr4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=k9HZf14fDu6oOt+SCUUNdCmjbQhEENXjcewPi1j+T6dYBNGkhZJ2ijShNcBFIlsko A/6Bap+S7ISA1qZ2+Pa05/UzM/PqfSGK5aHwN5yot4T5xJbjzqZLeKI45b51Xt1GWk wx4RyX3KhijzdrxV53Xewbh1JmP+t6mVb+tVbbuE= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729163AbgC3G1b (ORCPT ); Mon, 30 Mar 2020 02:27:31 -0400 Received: from mail.kernel.org ([198.145.29.99]:44482 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728489AbgC3G1b (ORCPT ); Mon, 30 Mar 2020 02:27:31 -0400 Received: from localhost (unknown [213.57.247.131]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id 8D39A20786; Mon, 30 Mar 2020 06:27:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585549650; bh=6IiawiuXQLOjYANKVy5JYWeqTQaiqOyWrx4qr3Digr4=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=B61jFnJ+19AmO4MzCyD6LVfNrxowHq3YDcHRRUznqVi9L5XTDcHgCC6XcAZp5jN8X QCrLXzMADoQQ7lEX+nnmZdu4wZED0DklHDsN4hYViRGm4cpxSDVmr6tE6m5428rO2W yi+IjNk0FOdDbotQpAaN4H7s/20F7CxgwwvUW4mI= Date: Sun, 29 Mar 2020 11:19:23 +0300 From: Leon Romanovsky To: Greg KH Cc: Jaewon Kim , vbabka@suse.cz, adobriyan@gmail.com, akpm@linux-foundation.org, labbott@redhat.com, sumit.semwal@linaro.org, minchan@kernel.org, ngupta@vflare.org, sergey.senozhatsky.work@gmail.com, kasong@redhat.com, bhe@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com, linux-api@vger.kernel.org, kexec@lists.infradead.org Subject: Re: [RFC PATCH v2 1/3] meminfo_extra: introduce meminfo extra Message-ID: <20200329081923.GD2454444@unreal> References: <20200323080503.6224-2-jaewon31.kim@samsung.com> <20200323095344.GB425358@kroah.com> <5E79CEB5.8070308@samsung.com> <20200324101110.GA2218981@kroah.com> <5E79F102.9080405@samsung.com> <20200324114645.GA2330984@kroah.com> <5E7A02BC.7020803@samsung.com> <20200329071907.GB2454444@unreal> <20200329072304.GA3909421@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <20200329072304.GA3909421@kroah.com> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sun, Mar 29, 2020 at 09:23:04AM +0200, Greg KH wrote: > On Sun, Mar 29, 2020 at 10:19:07AM +0300, Leon Romanovsky wrote: > > On Tue, Mar 24, 2020 at 09:53:16PM +0900, Jaewon Kim wrote: > > > > > > > > > On 2020년 03월 24일 20:46, Greg KH wrote: > > > > On Tue, Mar 24, 2020 at 08:37:38PM +0900, Jaewon Kim wrote: > > > >> > > > >> On 2020년 03월 24일 19:11, Greg KH wrote: > > > >>> On Tue, Mar 24, 2020 at 06:11:17PM +0900, Jaewon Kim wrote: > > > >>>> On 2020년 03월 23일 18:53, Greg KH wrote: > > > >>>>>> +int register_meminfo_extra(atomic_long_t *val, int shift, const char *name) > > > >>>>>> +{ > > > >>>>>> + struct meminfo_extra *meminfo, *memtemp; > > > >>>>>> + int len; > > > >>>>>> + int error = 0; > > > >>>>>> + > > > >>>>>> + meminfo = kzalloc(sizeof(*meminfo), GFP_KERNEL); > > > >>>>>> + if (!meminfo) { > > > >>>>>> + error = -ENOMEM; > > > >>>>>> + goto out; > > > >>>>>> + } > > > >>>>>> + > > > >>>>>> + meminfo->val = val; > > > >>>>>> + meminfo->shift_for_page = shift; > > > >>>>>> + strncpy(meminfo->name, name, NAME_SIZE); > > > >>>>>> + len = strlen(meminfo->name); > > > >>>>>> + meminfo->name[len] = ':'; > > > >>>>>> + strncpy(meminfo->name_pad, meminfo->name, NAME_BUF_SIZE); > > > >>>>>> + while (++len < NAME_BUF_SIZE - 1) > > > >>>>>> + meminfo->name_pad[len] = ' '; > > > >>>>>> + > > > >>>>>> + spin_lock(&meminfo_lock); > > > >>>>>> + list_for_each_entry_rcu(memtemp, &meminfo_head, list) { > > > >>>>>> + if (memtemp->val == val) { > > > >>>>>> + error = -EINVAL; > > > >>>>>> + break; > > > >>>>>> + } > > > >>>>>> + } > > > >>>>>> + if (!error) > > > >>>>>> + list_add_tail_rcu(&meminfo->list, &meminfo_head); > > > >>>>>> + spin_unlock(&meminfo_lock); > > > >>>>> If you have a lock, why are you needing rcu? > > > >>>> I think _rcu should be removed out of list_for_each_entry_rcu. > > > >>>> But I'm confused about what you meant. > > > >>>> I used rcu_read_lock on __meminfo_extra, > > > >>>> and I think spin_lock is also needed for addition and deletion to handle multiple modifiers. > > > >>> If that's the case, then that's fine, it just didn't seem like that was > > > >>> needed. Or I might have been reading your rcu logic incorrectly... > > > >>> > > > >>>>>> + if (error) > > > >>>>>> + kfree(meminfo); > > > >>>>>> +out: > > > >>>>>> + > > > >>>>>> + return error; > > > >>>>>> +} > > > >>>>>> +EXPORT_SYMBOL(register_meminfo_extra); > > > >>>>> EXPORT_SYMBOL_GPL()? I have to ask :) > > > >>>> I can use EXPORT_SYMBOL_GPL. > > > >>>>> thanks, > > > >>>>> > > > >>>>> greg k-h > > > >>>>> > > > >>>>> > > > >>>> Hello > > > >>>> Thank you for your comment. > > > >>>> > > > >>>> By the way there was not resolved discussion on v1 patch as I mentioned on cover page. > > > >>>> I'd like to hear your opinion on this /proc/meminfo_extra node. > > > >>> I think it is the propagation of an old and obsolete interface that you > > > >>> will have to support for the next 20+ years and yet not actually be > > > >>> useful :) > > > >>> > > > >>>> Do you think this is meaningful or cannot co-exist with other future > > > >>>> sysfs based API. > > > >>> What sysfs-based API? > > > >> Please refer to mail thread on v1 patch set - https://protect2.fireeye.com/url?k=16e3accc-4b2f6548-16e22783-0cc47aa8f5ba-935fe828ac2f6656&u=https://lkml.org/lkml/fancy/2020/3/10/2102 > > > >> especially discussion with Leon Romanovsky on https://protect2.fireeye.com/url?k=74208ed9-29ec475d-74210596-0cc47aa8f5ba-0bd4ef48931fec95&u=https://lkml.org/lkml/fancy/2020/3/16/140 > > > > I really do not understand what you are referring to here, sorry. I do > > > > not see any sysfs-based code in that thread. > > > Sorry. I also did not see actual code. > > > Hello Leon Romanovsky, could you elaborate your plan regarding sysfs stuff? > > > > Sorry for being late, I wasn't in "TO:", so missed the whole discussion. > > > > Greg, > > > > We need the exposed information for the memory optimizations (debug, not > > production) of our high speed NICs. Our devices (mlx5) allocates a lot of > > memory, so optimization there can help us to scale in SRIOV mode easier and > > be less constraint by the memory. > > Great, then use debugfs and expose what ever you want in what ever way > you want, no restrictions there, you do not need any type of kernel-wide > /proc file for that today. No argue here, just gave you an example why Jaewon's idea is worth to explore. > > > I want to emphasize that I don't like idea of extending /proc/* interface > > because it is going to be painful to grep on large machines with many > > devices. And I don't like the idea that every driver will need to register > > into this interface, because it will be abused almost immediately. > > I agree. > > > My proposal was to create new sysfs file by driver/core and put all > > information automatically there, for example, it can be > > /sys/devices/pci0000:00/0000:00:0c.0/meminfo > > ^^^^^^^ > > Nope, again, use debugfs, as sysfs is only one-value-per-file. Everything that is not /proc and one global file for whole kernel is fine by me. Debugfs is more than enough for us. Thanks > > thanks, > > greg k-h