From: Leon Romanovsky <leon@kernel.org>
To: Jaewon Kim <jaewon31.kim@samsung.com>,
Greg KH <gregkh@linuxfoundation.org>
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
Date: Sun, 29 Mar 2020 10:19:07 +0300 [thread overview]
Message-ID: <20200329071907.GB2454444@unreal> (raw)
In-Reply-To: <5E7A02BC.7020803@samsung.com>
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.
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.
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
next prev parent reply other threads:[~2020-03-29 7:19 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <CGME20200323080507epcas1p44cdb9ecb70a7a7395b3acddeda3cfd89@epcas1p4.samsung.com>
2020-03-23 8:05 ` [RFC PATCH v2 0/3] meminfo_extra: introduce meminfo extra Jaewon Kim
[not found] ` <CGME20200323080508epcas1p387c9c19b480da53be40fe5d51e76a477@epcas1p3.samsung.com>
2020-03-23 8:05 ` [RFC PATCH v2 1/3] " Jaewon Kim
2020-03-23 9:53 ` Greg KH
2020-03-24 9:11 ` Jaewon Kim
2020-03-24 10:11 ` Greg KH
2020-03-24 11:37 ` Jaewon Kim
2020-03-24 11:46 ` Greg KH
2020-03-24 12:53 ` Jaewon Kim
2020-03-24 13:19 ` Greg KH
2020-03-26 8:21 ` Jaewon Kim
2020-03-29 7:19 ` Leon Romanovsky [this message]
2020-03-29 7:23 ` Greg KH
2020-03-29 8:19 ` Leon Romanovsky
2020-03-25 18:23 ` Alexey Dobriyan
2020-03-23 12:00 ` Dave Young
[not found] ` <CGME20200323080508epcas1p2dfe6517169a65936e5ab10c4e63a19a7@epcas1p2.samsung.com>
2020-03-23 8:05 ` [RFC PATCH v2 2/3] mm: zsmalloc: include zs page size in " Jaewon Kim
[not found] ` <CGME20200323080508epcas1p3c68190cd46635b9ff026a4ae70fc7a3b@epcas1p3.samsung.com>
2020-03-23 8:05 ` [RFC PATCH v2 3/3] android: ion: include system heap " Jaewon Kim
2020-03-23 9:49 ` Greg KH
2020-03-25 18:12 ` [RFC PATCH v2 0/3] meminfo_extra: introduce " Alexey Dobriyan
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