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=-0.8 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, 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 3798BC2D0ED for ; Sun, 29 Mar 2020 07:19:14 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id E3FFA2076A for ; Sun, 29 Mar 2020 07:19:13 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=kernel.org header.i=@kernel.org header.b="rrk/WBcx" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org E3FFA2076A Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; 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Sun, 29 Mar 2020 07:19:12 +0000 (UTC) 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 BDCD620748; Sun, 29 Mar 2020 07:19:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585466351; bh=X3/JmZQnZmXAjPb34qJAtFnIg9UxjJZFWi6e1u3/s8o=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=rrk/WBcxa0aySYOzNkL/+6q6kEKWU8t+upenVycMvwovM8zNmKR7rh2MqqseymlXC oYdlPYhtGczT+tFxM/bZqQECaRwKZt3kcwYPL/jo1kk+3SKKIcW60rlLmXVHURr+kI 5S3+TiE/u4DAQdc7wjnQwz2nV1tzOaUBK3QB+6pk= Date: Sun, 29 Mar 2020 10:19:07 +0300 From: Leon Romanovsky To: Jaewon Kim , Greg KH Cc: 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: <20200329071907.GB2454444@unreal> References: <20200323080503.6224-1-jaewon31.kim@samsung.com> <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> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <5E7A02BC.7020803@samsung.com> Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Tue, Mar 24, 2020 at 09:53:16PM +0900, Jaewon Kim wrote: > > > On 2020=EB=85=84 03=EC=9B=94 24=EC=9D=BC 20:46, Greg KH wrote: > > On Tue, Mar 24, 2020 at 08:37:38PM +0900, Jaewon Kim wrote: > >> > >> On 2020=EB=85=84 03=EC=9B=94 24=EC=9D=BC 19:11, Greg KH wrote: > >>> On Tue, Mar 24, 2020 at 06:11:17PM +0900, Jaewon Kim wrote: > >>>> On 2020=EB=85=84 03=EC=9B=94 23=EC=9D=BC 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 =3D 0; > >>>>>> + > >>>>>> + meminfo =3D kzalloc(sizeof(*meminfo), GFP_KERNEL); > >>>>>> + if (!meminfo) { > >>>>>> + error =3D -ENOMEM; > >>>>>> + goto out; > >>>>>> + } > >>>>>> + > >>>>>> + meminfo->val =3D val; > >>>>>> + meminfo->shift_for_page =3D shift; > >>>>>> + strncpy(meminfo->name, name, NAME_SIZE); > >>>>>> + len =3D strlen(meminfo->name); > >>>>>> + meminfo->name[len] =3D ':'; > >>>>>> + strncpy(meminfo->name_pad, meminfo->name, NAME_BUF_SIZE); > >>>>>> + while (++len < NAME_BUF_SIZE - 1) > >>>>>> + meminfo->name_pad[len] =3D ' '; > >>>>>> + > >>>>>> + spin_lock(&meminfo_lock); > >>>>>> + list_for_each_entry_rcu(memtemp, &meminfo_head, list) { > >>>>>> + if (memtemp->val =3D=3D val) { > >>>>>> + error =3D -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 ment= ioned 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 futu= re > >>>> sysfs based API. > >>> What sysfs-based API? > >> Please refer to mail thread on v1 patch set - https://protect2.firee= ye.com/url?k=3D16e3accc-4b2f6548-16e22783-0cc47aa8f5ba-935fe828ac2f6656&u= =3Dhttps://lkml.org/lkml/fancy/2020/3/10/2102 > >> especially discussion with Leon Romanovsky on https://protect2.firee= ye.com/url?k=3D74208ed9-29ec475d-74210596-0cc47aa8f5ba-0bd4ef48931fec95&u= =3Dhttps://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 st= uff? 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 a= nd be less constraint by the memory. 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 registe= r into this interface, because it will be abused almost immediately. 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 ^^^^^^^ Thanks