From: Yafang Shao <laoar.shao@gmail.com>
To: Michal Hocko <mhocko@kernel.org>
Cc: Johannes Weiner <hannes@cmpxchg.org>,
Andrew Morton <akpm@linux-foundation.org>,
Roman Gushchin <guro@fb.com>, Chris Down <chris@chrisdown.name>,
Linux MM <linux-mm@kvack.org>
Subject: Re: [PATCH 0/3] mm: improve proportional memcg protection
Date: Tue, 28 Apr 2020 20:25:49 +0800 [thread overview]
Message-ID: <CALOAHbBDXRXX9c-svbuuoBRtAZtfz0FLz-ma2K+PkFeVC2yQGA@mail.gmail.com> (raw)
In-Reply-To: <20200428104300.GN28637@dhcp22.suse.cz>
On Tue, Apr 28, 2020 at 6:43 PM Michal Hocko <mhocko@kernel.org> wrote:
>
> On Tue 28-04-20 16:22:46, Yafang Shao wrote:
> > On Tue, Apr 28, 2020 at 4:05 PM Michal Hocko <mhocko@kernel.org> wrote:
> > >
> > > On Tue 28-04-20 09:45:27, Yafang Shao wrote:
> > > [...]
> > > > Seems we can't get an agreement on how to improve current code.
> > > > So I will submit a patch to revert the commit 9783aa9917f8 ("mm,
> > > > memcg: proportional memory.{low,min} reclaim") first.
> > >
> > > My current understanding is that the issue we are discussing here is
> > > mostly theoretical. Your changelog doesn't really talk about any real
> > > life workloads that would be suffering.
> >
> > Is real life workload really important ?
>
> It is really important to make cost vs. benefit decisions. Like whether
> to rever the said commit or not.
>
> > If so, why an issue[1] occured in the real workload report by me in
> > 2019 that memcg proection can't protect inactive pages (inodes) is
> > ignored again and again ?
>
> I do not think it is ignored. IIRC there was not an agreement on the way
> to fix this. I could get involved very much because there were other
> higher priority things to take care. People are simply busy.
>
In your theory - issues with real life workload has a higher priority,
you should pay more attention to that one, rather than wasting your
time on a comment war in this one.
Alright, the comment war really wastes time, that is not expected by me.
So let's turn back to the techichal discussion.
> > So I'm questioning that what is the real life workload ?
>
> It is a workload which does something useful for their users.
> [...]
> > > So it would be really more helpful to not insist on unrelated
> > > implementation details and focus on two things 1) split up the effective
> > > values calculation from the predicate (cleanup without any functional
> > > changes) 2) make the calculation more robust against racing reclaimers.
> > >
> >
> > Another thing should be considered as well, 0) don't access
> > memroy.emin and elow in get_scan_count().
>
> If you can achieve the gradual transition over protections by other
> means then I am really interested in more details.
sc->protection
I make my statement again - accessing the realy fragile emin & elow
in very deep reclaiming code is a totally horrible HACK, that is the
root of all evil.
--
Thanks
Yafang
next prev parent reply other threads:[~2020-04-28 12:26 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-25 15:24 Yafang Shao
2020-04-25 15:24 ` [PATCH 1/3] mm: move struct scan_control into internal.h Yafang Shao
2020-04-25 15:24 ` [PATCH 2/3] mm: add reclaim context as a new parameter in mem_cgroup_protected() Yafang Shao
2020-04-25 15:24 ` [PATCH 3/3] mm: improvements on memcg protection functions Yafang Shao
2020-04-27 9:40 ` Michal Hocko
2020-04-27 10:09 ` Yafang Shao
2020-04-27 10:50 ` Michal Hocko
2020-04-27 11:06 ` Yafang Shao
2020-04-27 11:24 ` Michal Hocko
2020-04-27 11:32 ` Yafang Shao
2020-04-27 17:05 ` [PATCH 0/3] mm: improve proportional memcg protection Johannes Weiner
2020-04-28 1:45 ` Yafang Shao
2020-04-28 3:37 ` Johannes Weiner
2020-04-28 6:00 ` Yafang Shao
2020-04-28 8:05 ` Michal Hocko
2020-04-28 8:22 ` Yafang Shao
2020-04-28 10:43 ` Michal Hocko
2020-04-28 12:25 ` Yafang Shao [this message]
2020-04-28 12:42 ` Michal Hocko
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