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Tue, 24 Mar 2020 18:11:25 +0900 (KST) Received: from [10.253.104.82] (unknown [10.253.104.82]) by epsmtip1.samsung.com (KnoxPortal) with ESMTPA id 20200324091123epsmtip1e79651d15bbe092e7a442b916ede3129~-Mne7lSLB3263532635epsmtip1J; Tue, 24 Mar 2020 09:11:23 +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: <5E79CEB5.8070308@samsung.com> Date: Tue, 24 Mar 2020 18:11:17 +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: <20200323095344.GB425358@kroah.com> X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFnrBJsWRmVeSWpSXmKPExsWy7bCmnu6+c5VxBne2s1pMb/SymLN+DZvF +Qe/2CyaF69ns+jePJPRYvm704wWu09/ZbJYuecHk8WUX0uZLTZ/72CzuLxrDpvFvTX/WS2W fX3PbrGhZRa7xaMJk5gsTt39zG4xu7GP0UHQY+esu+wem1Z1snls+jSJ3ePOtT1sHidm/Gbx 2D93DbvH5iX1Hu/3XWXzOLPgCLvHzk+bWT0+b5IL4I7KsclITUxJLVJIzUvOT8nMS7dV8g6O d443NTMw1DW0tDBXUshLzE21VXLxCdB1y8wBekpJoSwxpxQoFJBYXKykb2dTlF9akqqQkV9c YquUWpCSU2BoUKBXnJhbXJqXrpecn2tlaGBgZApUmZCT0bFiPmPBG/mK9Yu2szYwHpfsYuTk kBAwkfjwfT8jiC0ksINRomNLcRcjF5D9iVHizJdvbBDON0aJSXcvM8J0LDjxGCqxl1Hi/K+V 7BDOW0aJky032UCqhAXcJP5tPQ9miwhoSLw8eosFpIhZ4DuTxPHFX5hAEmwC2hLvF0xiBbF5 BbQkFk7qA1vBIqAqMW3iExYQW1QgQmLH3I+MEDWCEidngsQ5ODgFDCQ6XtmChJkF5CWat85m BpkvIXCKXWLd4r+sEKe6SJxY/IcNwhaWeHV8CzuELSXx+d1eNoiGZkaJtzM3M0I4LYwSdzf1 Qj1qLNHbc4EZZBuzgKbE+l36EGFFiZ2/5zJCbOaTePe1hxWkREKAV6KjTQiiRE2i5dlXqBtk JP7+ewZV4iFx/p8aJKxfMkqs+acxgVFhFpLPZiF5ZxbC3gWMzKsYxVILinPTU4sNC0yRY3gT IziVa1nuYDx2zucQowAHoxIP74ZpFXFCrIllxZW5hxglOJiVRHg3pwKFeFMSK6tSi/Lji0pz UosPMZoCA3sis5Rocj4wz+SVxBuaGhkbG1uYmJmbmRorifNOvZ4TJySQnliSmp2aWpBaBNPH xMEp1cAY7jHPYunHTO3MR0u4+/75Kl5mXsyd8cpw2w4V6z6HVrMJVyy3dB6wYXiYyDJjk5tc U5i1ckh4zeVM8Z19yw9Nn3z+k8u1XV+ns95xuZp3+DXHl4DN8fm7U+qawxde++3qsv9J14vl 3DGbZV78e/iwQvVYVFLQysvZFzfMi92Su5331Fo+qWNNSizFGYmGWsxFxYkAkolgUfsDAAA= X-Brightmail-Tracker: H4sIAAAAAAAAA+NgFtrBIsWRmVeSWpSXmKPExsWy7bCSnO7ec5VxBv0nxS2mN3pZzFm/hs3i /INfbBbNi9ezWXRvnslosfzdaUaL3ae/Mlms3PODyWLKr6XMFpu/d7BZXN41h83i3pr/rBbL vr5nt9jQMovd4tGESUwWp+5+ZreY3djH6CDosXPWXXaPTas62Tw2fZrE7nHn2h42jxMzfrN4 7J+7ht1j85J6j/f7rrJ5nFlwhN1j56fNrB6fN8kFcEdx2aSk5mSWpRbp2yVwZXSsmM9Y8Ea+ Yv2i7awNjMcluxg5OSQETCQWnHjM1sXIxSEksJtR4k/DLFaIhIzEm/NPWboYOYBsYYnDh4sh al4zSmw/180MUiMs4Cbxb+t5NhBbREBD4uXRWywQRS8ZJSb+PgXmMAt8Z5K41HcIrIpNQFvi /YJJYBt4BbQkFk7qYwSxWQRUJaZNfMICYosKREisXneNGaJGUOLkzCdgV3AKGEh0vLIFMZkF 1CXWzxMCqWAWkJdo3jqbeQKj4CwkDbMQqmYhqVrAyLyKUTK1oDg3PbfYsMAwL7Vcrzgxt7g0 L10vOT93EyM4PrU0dzBeXhJ/iFGAg1GJh5djZkWcEGtiWXFl7iFGCQ5mJRHezalAId6UxMqq 1KL8+KLSnNTiQ4zSHCxK4rxP845FCgmkJ5akZqemFqQWwWSZODilGhi7/hjbPHkgOmc2n8rx 8L7rHJtnWc+e68UhILcy5u7rG+xXD3xxP91q/2eJLFNCwsWHRufspiqrLrqjd+x05/HquSFF TWsZH9aVuH9Y5bAv/4pYiJLfFQP/pvhmJff4Zb9mnZsTtXmxUdyjeescHkZasIVVuRQa9GaH biplaTm1pmPVSR/bebOVWIozEg21mIuKEwHTU5jhywIAAA== X-CMS-MailID: 20200324091125epcas1p43356a6bb4bf77d743551fed71e35cbc4 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> 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 2020=EB=85=84 03=EC=9B=94 23=EC=9D=BC 18:53, Greg KH wrote: > On Mon, Mar 23, 2020 at 05:05:01PM +0900, Jaewon Kim wrote: >> Provide APIs to drivers so that they can show its memory usage on >> /proc/meminfo_extra. >> >> int register_meminfo_extra(atomic_long_t *val, int shift, >> const char *name); >> int unregister_meminfo_extra(atomic_long_t *val); > Nit, isn't it nicer to have the subsystem name first: > meminfo_extra_register() > meminfo_extra_unregister() > ? OK. Name can be changed. > > >> Signed-off-by: Jaewon Kim >> --- >> v2: move to /proc/meminfo_extra as a new file, meminfo_extra.c >> use rcu to reduce lock overhead >> v1: print info at /proc/meminfo >> --- >> fs/proc/Makefile | 1 + >> fs/proc/meminfo_extra.c | 123 +++++++++++++++++++++++++++++++++++++++= +++++++++ >> include/linux/mm.h | 4 ++ >> mm/page_alloc.c | 1 + >> 4 files changed, 129 insertions(+) >> create mode 100644 fs/proc/meminfo_extra.c >> >> diff --git a/fs/proc/Makefile b/fs/proc/Makefile >> index bd08616ed8ba..83d2f55591c6 100644 >> --- a/fs/proc/Makefile >> +++ b/fs/proc/Makefile >> @@ -19,6 +19,7 @@ proc-y +=3D devices.o >> proc-y +=3D interrupts.o >> proc-y +=3D loadavg.o >> proc-y +=3D meminfo.o >> +proc-y +=3D meminfo_extra.o >> proc-y +=3D stat.o >> proc-y +=3D uptime.o >> proc-y +=3D util.o >> diff --git a/fs/proc/meminfo_extra.c b/fs/proc/meminfo_extra.c >> new file mode 100644 >> index 000000000000..bd3f0d2b7fb7 >> --- /dev/null >> +++ b/fs/proc/meminfo_extra.c >> @@ -0,0 +1,123 @@ >> +// SPDX-License-Identifier: GPL-2.0 >> +#include >> +#include >> +#include >> +#include >> + >> +static void show_val_kb(struct seq_file *m, const char *s, unsigned l= ong num) >> +{ >> + seq_put_decimal_ull_width(m, s, num << (PAGE_SHIFT - 10), 8); >> + seq_write(m, " kB\n", 4); >> +} >> + >> +static LIST_HEAD(meminfo_head); >> +static DEFINE_SPINLOCK(meminfo_lock); >> + >> +#define NAME_SIZE 15 >> +#define NAME_BUF_SIZE (NAME_SIZE + 2) /* ':' and '\0' */ >> + >> +struct meminfo_extra { >> + struct list_head list; >> + atomic_long_t *val; >> + int shift_for_page; >> + char name[NAME_BUF_SIZE]; >> + char name_pad[NAME_BUF_SIZE]; >> +}; >> + >> +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 (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 o= n cover page. I'd like to hear your opinion on this /proc/meminfo_extra node. Do you think this is meaningful or cannot co-exist with other future sysf= s based API.