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Tue, 24 Mar 2020 12:53:17 +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: <5E7A02BC.7020803@samsung.com> Date: Tue, 24 Mar 2020 21:53:16 +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: <20200324114645.GA2330984@kroah.com> Content-Transfer-Encoding: 8bit X-Brightmail-Tracker: H4sIAAAAAAAAA02Tf0wTZxjH8961d8Wt5iw6nzQTu0vQwQJcKYV3iywmY+Q2XcJmtiz+0e6k JyW7/livOOGf4dowx2RW5nRUIMTCcA0MbYEVFQ0wgz8WMVtkcRHndDEBB41gZcMM13KY8d/3 eZ7P8z4/3vfVkLopSq+pdHpFj1OQWGqVqn8kKzfnPFFj4QJH8vDRfW/i5p4uCo/dXqCwL9RD 4S+iTQh3zlxB+MyVBIG/O/s3gQ8vdJA4Or+fwr+cbqbwra4navxtIk7jk/4gje8EGgl8eWKO xsf2fYm2ruEHghM0Hwl/TvGR2Uaavzl+luIvfvNYxZ9v6aL5aPsnfPzcdYr/qe1Hmh+Yjar5 uUhG2TM7pS12UbCJHoPoLHfZKp0Vxey2HdbXrOZCzphjfBkXsQan4BCL2ZLtZTmllVJyKNaw R5Cqkq4yQZbZvFe3eFxVXtFgd8neYlZ02yS3kXPnyoJDrnJW5Ja7HK8YOS7fnCQ/kOx/HZ2i 3bdMe0PB63QtimfVozQNMAXwwz+d6nq0SqNjYgiOHB5EqYCOmUXQ/dCjBB4hqB8YVz3NuNQb WM4YRBAMhwjFmEYwON5Kpqh0phQW+8aolF7LvAiTF35TpSCSmSdgNPSQSAUo5iWItzWqU1rL ZMNnZ0bplFYxmXAudmPJv455H2ItD5DCrIFLTX8utZHGGGHh98gSQzIbwdd3jEwVAOYyDdGv PqWUXkvg0YODtKLTYWq0d1nrYfJgHa0k+BBMN0WRYvgRTEQakEKZoOHAteSxmmSJLOg5nae4 X4CBxy1IqbwaZhIH1CkEGC3sr9MpyCbw30uoFf08/Lt4bxnhYWxxk7KtBAFD3T4qgAzBFbMF V8wT/L9wGyLD6DnRLTsqRNnoNq284whaeufZRTF08ur2YcRoEPustvZutUWnFvbI1Y5hBBqS XauNinstOq1NqK4RPS6rp0oS5WFkTq77EKlfV+5K/hqn12o055tMJlxQWFRoNrHrtV//Kll0 TIXgFT8URbfoeZpHaNL0tYi4OxQz+L2vd0R6semtpv7KznCPHA1zh/q3tsfqbvpLdxzveDIm 7Sr42X5icmTu46uF9d9nwIb53NZizjqt3+jO3BC4cC3/fu87b6weak7v7OYmbuz6434oPX68 Lye7xlBy29Lev96w+72M1o/UM7a3fb6pd0caStPaM52nuM13SFYl2wVjNumRhf8ALX7jk/0D AAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrFIsWRmVeSWpSXmKPExsWy7bCSnO4+pqo4gwfXZC2mN3pZzFm/hs3i /INfbBbNi9ezWXRvnslosfzdaUaL3ae/Mlms3PODyWLKr6XMFpu/d7BZXN41h83i3pr/rBbL vr5nt9jQMovd4tGESUwWp+5+ZreY3djH6CDosXPWXXaPTas62Tw2fZrE7nHn2h42jxMzfrN4 7J+7ht1j85J6j/f7rrJ5nFlwhN1j56fNrB6fN8kFcEdx2aSk5mSWpRbp2yVwZbyZ/oq94J5x xeJZV9kbGN9rdjFyckgImEic3DKBtYuRi0NIYDejxOnJK1kgEjISb84/BbI5gGxhicOHi0HC QgKvGSUOLwwCsYUF3CT+bT3PBmKLCGhIvDx6iwVizlcmiccnTjCBOMwC35kkLvUdAqtiE9CW eL9gEiuIzSugJdG++zg7iM0ioCqxb8dNsLioQITE6nXXmCFqBCVOznwCdhCngKHEr/ubwGqY BdQl/sy7xAxhy0s0b53NPIFRcBaSlllIymYhKVvAyLyKUTK1oDg3PbfYsMAwL7Vcrzgxt7g0 L10vOT93EyM4RrU0dzBeXhJ/iFGAg1GJh1frYWWcEGtiWXFl7iFGCQ5mJRHezakVcUK8KYmV ValF+fFFpTmpxYcYpTlYlMR5n+YdixQSSE8sSc1OTS1ILYLJMnFwSjUwLnc+6P297pAIJ5u7 6d+yrPVVW9dUhMwoerA2oEFPhs3w6DSuCdptaX8qDN6mts48EWloLeHfFPTTvl7ipcmpSdk1 hkt/rjR8YurqzBzNNZNhxrLNqucCjFXe/SsV7Dkk5escbN1+8NFLw4zeczrcdjvWxTxnKHzB 3/SrkSmD7VTBrBns9c+VWIozEg21mIuKEwGN5ZnMzQIAAA== X-CMS-MailID: 20200324125318epcas1p2f378c2492fab03b9bd143cdf5c77bfe8 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> <5E79F102.9080405@samsung.com> <20200324114645.GA2330984@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 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? > > And try to use lore.kernel.org, lkml.org doesn't always work and we have > no control over that :( > >>> 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. > Ok, so what does Android have to do with this? Some driver in Android platform may use my API to show its memory usage. > >> 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. > Why? Who wants that? What would userspace do with that? And what > exactly do you want to show? > > Is this just a debugging thing? Then use debugfs for that, not proc. > Isn't that what the DRM developers are starting to do? > >> Additionally I'd like to see all those hidden memory in OutOfMemory log. > How is anything hidden, can't you see it in the slab information? > Let me explain more. 0. slab As I said in cover page, this is not for memory allocated by slab. I'd like to know where huge memory has gone. Those are directly allocated by alloc_pages instead of slab. /proc/slabinfo does not show this information. 1. /proc/meminfo_extra /proc/meminfo_extra could be debugging thing to see memory status at a certain time. But it, I think, is also basic information rather than just for debugging. It is similar with /proc/meminfo which is in procfs instead of debugfs. 2. oom log oom log in show_mem is more than just debugging. As existing oom log shows much memory information, I think we need the hidden memory info. Without these information, we do NOT know oom reason because other traditional stats are not enough. >> 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 > So what does this show you? That someone is takign a ton of ION memory > for some unknown use? What can you do with that? What would you do > with that? We may not know exact memory owner. But we can narrow down. Anyway I think this is meaningful instead of no clue. > > And memory is almost never assigned to a "driver", it is assigned to a > "device" that uses it. Drivers can handle multiple devices at the same > time, so why would you break this down by drivers? Are you assuming > that a driver only talks to one piece of hardware? Yes a driver may support several devices. I don't know if it same on an embedded device. Anyway I think the idea works even for several devices, although the driver should distinguish memory usage for each device and should register each memory stat. > > I think you need a much better use case for all of this other than > "wouldn't it be nice to see some numbers", as that isn't going to help > anyone out in the end. Sorry. As of now, I do not know other better use case, but I still think memory information should cover most of memory usage. Huge memory consumed by driver or other core logic should be shown in OoM. > > thanks, > > greg k-h > >