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Tue, 24 Mar 2020 11:37:39 +0000 (GMT) Subject: Re: [RFC PATCH v2 1/3] meminfo_extra: introduce meminfo extra To: Greg KH Cc: leon@kernel.org, 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 From: Jaewon Kim Message-ID: <5E79F102.9080405@samsung.com> Date: Tue, 24 Mar 2020 20:37:38 +0900 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.2 MIME-Version: 1.0 In-Reply-To: <20200324101110.GA2218981@kroah.com> Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrBJsWRmVeSWpSXmKPExsWy7bCmvi7rx8o4gzcd/BbTG70s5qxfw2Zx /sEvNovmxevZLLo3z2S0WP7uNKPF7tNfmSxW7vnBZDHl11Jmi83fO9gsLu+aw2Zxb81/Votl X9+zW2xomcVu8WjCJCaLU3c/s1vMbuxjdBD02DnrLrvHplWdbB6bPk1i97hzbQ+bx4kZv1k8 9s9dw+6xeUm9x/t9V9k8ziw4wu6x89NmVo/Pm+QCuKNybDJSE1NSixRS85LzUzLz0m2VvIPj neNNzQwMdQ0tLcyVFPISc1NtlVx8AnTdMnOAnlJSKEvMKQUKBSQWFyvp29kU5ZeWpCpk5BeX 2CqlFqTkFBgaFOgVJ+YWl+al6yXn51oZGhgYmQJVJuRkvOwTLLgvVXHmx0SWBsYTol2MHBwS AiYST47IdjFycQgJ7GCU2HJpFyuE84lRou/heRYI5xujxJPvH5i7GDnBOhqX32AFsYUE9jJK 3HtqA1H0llHi0Lmj7CAJYQE3iX9bz7OB2CICGhIvj94Cm8Qs8J1J4vjiL0wgCTYBbYn3CyaB TeIV0JJYveI62AYWAVWJvW9vgNmiAhESO+Z+ZISoEZQ4OfMJC4jNKWAo8XPDH7BlzALyEs1b ZzODLJAQOMUu8W7pfiaIU10kOiafg7KFJV4d38IOYUtJfH63lw2ioZlR4u3MzYwQTgujxN1N vYwQVcYSvT0XmEHBxCygKbF+lz5EWFFi5++5jBCb+STefe1hhYQkr0RHmxBEiZpEy7OvrBC2 jMTff8+gSjwkzv9Tg4TWemBArN7AOoFRYRaS32Yh+WcWwuIFjMyrGMVSC4pz01OLDQtMkWN4 EyM4lWtZ7mA8ds7nEKMAB6MSD2/D48o4IdbEsuLK3EOMEhzMSiK8m1Mr4oR4UxIrq1KL8uOL SnNSiw8xmgKDeyKzlGhyPjDP5JXEG5oaGRsbW5iYmZuZGiuJ8069nhMnJJCeWJKanZpakFoE 08fEwSnVwHiw7V369uefJjBsWLQs99nHmwv+yZryrXWwOVJgMf/t+n88KocN9ZvL1xy/8aAg X+6b7uY47r9Wtget/CN/31jwl/2ljuBLhre/+1SlvJtC1k6y8d35zE3kLmv9TfEppv1qfV2l 0+5X6gbeZX5idiKoPHzaqy7uV+eOH+zcscf8kvqPI966D8KUWIozEg21mIuKEwFBKliZ+wMA AA== X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrFIsWRmVeSWpSXmKPExsWy7bCSvC7Lx8o4g6592hbTG70s5qxfw2Zx /sEvNovmxevZLLo3z2S0WP7uNKPF7tNfmSxW7vnBZDHl11Jmi83fO9gsLu+aw2Zxb81/Votl X9+zW2xomcVu8WjCJCaLU3c/s1vMbuxjdBD02DnrLrvHplWdbB6bPk1i97hzbQ+bx4kZv1k8 9s9dw+6xeUm9x/t9V9k8ziw4wu6x89NmVo/Pm+QCuKO4bFJSczLLUov07RK4Ml72CRbcl6o4 82MiSwPjCdEuRk4OCQETicblN1i7GLk4hAR2M0rc2bydBSIhI/Hm/FMgmwPIFpY4fLgYouY1 o8SW7g4mkBphATeJf1vPs4HYIgIaEi+P3mKBKFrPJLGz9x2YwyzwnUniUt8hsCo2AW2J9wsm sYLYvAJaEqtXXGcGsVkEVCX2vr0BZosKREisXneNGaJGUOLkzCdgF3EKGEr83PCHHcRmFlCX +DPvEjOELS/RvHU28wRGwVlIWmYhKZuFpGwBI/MqRsnUguLc9NxiwwLDvNRyveLE3OLSvHS9 5PzcTYzgGNXS3MF4eUn8IUYBDkYlHl6th5VxQqyJZcWVuYcYJTiYlUR4N6dWxAnxpiRWVqUW 5ccXleakFh9ilOZgURLnfZp3LFJIID2xJDU7NbUgtQgmy8TBKdXAOP1pjNGxW8UvvmlMeskt 2P1n8busvvVP3t1XTDNo6InM/GWTbb/QyiL0g+PtW7m6rRzs+/wDJ9jt3lLAutoj8q/bweik xWVruta2Ht/+9Ycc766dM4873Zn685nwviNB/zgXRDasX2klti7Cae+snXzrDhfeOW5zVWC6 xJVN9h/Loib2GIV2limxFGckGmoxFxUnAgC9Jb9gzQIAAA== X-CMS-MailID: 20200324113740epcas1p105dbc87fedfa534c2d6b6a8ad515fda0 X-Msg-Generator: CA Content-Type: text/plain; charset="utf-8" X-Sendblock-Type: SVC_REQ_APPROVE CMS-TYPE: 101P DLP-Filter: Pass X-CFilter-Loop: Reflected X-CMS-RootMailID: 20200323080508epcas1p387c9c19b480da53be40fe5d51e76a477 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> Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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://lkml.org/lkml/fancy/2020/3/10/2102 especially discussion with Leon Romanovsky on https://lkml.org/lkml/fancy/2020/3/16/140 > > I still don't know _why_ you want this. The ION stuff is not needed as > that code is about to be deleted, so who else wants this? What is the > use-case for it that is so desperately needed that parsing > yet-another-proc file is going to solve the problem? In my Android device, there are graphic driver memory, zsmalloc memory except ION. I don't know other cases in other platform. Not desperately needed but I think we need one userspace knob to see overall hidden huge memory. Additionally I'd like to see all those hidden memory in OutOfMemory log. This is useful to get clue to find memory hogger. i.e.) show_mem on oom <6>[ 420.856428] Mem-Info: <6>[ 420.856433] IonSystemHeap:32813kB ZsPages:44114kB GraphicDriver::13091kB <6>[ 420.856450] active_anon:957205 inactive_anon:159383 isolated_anon:0 Thank you Jaewon Kim > > thanks, > > greg k-h > >