linux-kernel - Re: [PATCH 1/1] mm: introduce process

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Date:   Mon, 5 Jul 2021 09:41:54 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Christian Brauner <christian.brauner@...ntu.com>,
        Suren Baghdasaryan <surenb@...gle.com>
Cc:     Andy Lutomirski <luto@...nel.org>,
        Johannes Weiner <hannes@...xchg.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Michal Hocko <mhocko@...nel.org>,
        Michal Hocko <mhocko@...e.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Roman Gushchin <guro@...com>, Rik van Riel <riel@...riel.com>,
        Minchan Kim <minchan@...nel.org>,
        Christian Brauner <christian@...uner.io>,
        Christoph Hellwig <hch@...radead.org>,
        Oleg Nesterov <oleg@...hat.com>, Jann Horn <jannh@...gle.com>,
        Shakeel Butt <shakeelb@...gle.com>,
        Tim Murray <timmurray@...gle.com>,
        Linux API <linux-api@...r.kernel.org>,
        Linux-MM <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Android Kernel Team <kernel-team@...roid.com>
Subject: Re: [PATCH 1/1] mm: introduce process_reap system call

On 02.07.21 17:27, Christian Brauner wrote:
> On Thu, Jul 01, 2021 at 03:59:48PM -0700, Suren Baghdasaryan wrote:
>> On Wed, Jun 30, 2021 at 5:44 PM Andy Lutomirski <luto@...nel.org> wrote:
>>>
>>> On Wed, Jun 30, 2021 at 2:45 PM Johannes Weiner <hannes@...xchg.org> wrote:
>>>>
>>>> On Wed, Jun 30, 2021 at 11:51:36AM -0700, Suren Baghdasaryan wrote:
>>>>> On Wed, Jun 30, 2021 at 11:26 AM Andy Lutomirski <luto@...nel.org> wrote:
>>>>>> Also, please consider removing all mention of the word "reap" from the
>>>>>> user API.  For better or for worse, "reap" in UNIX refers to what
>>>>>> happens when a dead task gets wait()ed.  I sincerely wish I could go
>>>>>> back in time and gently encourage whomever invented that particular
>>>>>> abomination to change their mind, but my time machine doesn't work.
>>>>>
>>>>> I see. Thanks for the note. How about process_mem_release() and
>>>>> replacing reap with release everywhere?
>>>>
>>>> I don't quite understand the objection. This syscall works on tasks
>>>> that are at the end of their life, right? Isn't something like
>>>> process_mreap() establishing exactly the mental link we want here?
>>>> Release is less descriptive for what this thing is to be used for.
>>>
>>> For better or for worse, "reap" means to make a zombie pid go away.
>>>  From the description, this new operation takes a dying process (not
>>> necessarily a zombie yet) and aggressively frees its memory.  This is
>>> a different optioneration.
>>>
>>> How about "free_dying_process_memory"?
>>
>> process_mreap sounds definitely better and in line with names like
>> process_madvise. So maybe we can use it?
> 
> That one was my favorite from the list I gave too but maybe we can
> satisfy Andy too if we use one of:
> - process_mfree()
> - process_mrelease()
> 

FWIW, I tend to like process_mrelease(), due to the implied "release" 
("free the memory if there are no other references") semantics. Further, 
a new syscall feels cleaner than some magic sysfs/procfs toggle. Just my 
2 cents.

-- 
Thanks,

David / dhildenb