From: Zhaoyang Huang <huangzhaoyang@gmail.com>
To: Michal Hocko <mhocko@suse.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Vladimir Davydov <vdavydov.dev@gmail.com>,
Zhaoyang Huang <zhaoyang.huang@unisoc.com>,
"open list:MEMORY MANAGEMENT" <linux-mm@kvack.org>,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH] mm: have kswapd only reclaiming use min protection on memcg
Date: Wed, 27 Oct 2021 17:19:56 +0800 [thread overview]
Message-ID: <CAGWkznHrZ=Y3kG5j5aYdTV2294QGrQbM6251zcdGphzCGUP6dw@mail.gmail.com> (raw)
In-Reply-To: <YXkNJjD4axYlmqQ5@dhcp22.suse.cz>
On Wed, Oct 27, 2021 at 4:26 PM Michal Hocko <mhocko@suse.com> wrote:
>
> On Wed 27-10-21 15:46:19, Zhaoyang Huang wrote:
> > On Wed, Oct 27, 2021 at 3:20 PM Michal Hocko <mhocko@suse.com> wrote:
> > >
> > > On Wed 27-10-21 15:01:50, Huangzhaoyang wrote:
> > > > From: Zhaoyang Huang <zhaoyang.huang@unisoc.com>
> > > >
> > > > For the kswapd only reclaiming, there is no chance to try again on
> > > > this group while direct reclaim has. fix it by judging gfp flag.
> > >
> > > There is no problem description (same as in your last submissions. Have
> > > you looked at the patch submission documentation as recommended
> > > previously?).
> > >
> > > Also this patch doesn't make any sense. Both direct reclaim and kswapd
> > > use a gfp mask which contains __GFP_DIRECT_RECLAIM (see balance_pgdat
> > > for the kswapd part)..
> > ok, but how does the reclaiming try with memcg's min protection on the
> > alloc without __GFP_DIRECT_RECLAIM?
>
> I do not follow. There is no need to protect memcg if the allocation
> request doesn't have __GFP_DIRECT_RECLAIM because that would fail the
> charge if a hard limit is reached, see try_charge_memcg and
> gfpflags_allow_blocking check.
>
> Background reclaim, on the other hand never breaches reclaim protection.
>
> What is the actual problem you want to solve?
Imagine there is an allocation with gfp_mask & ~GFP_DIRECT_RECLAIM and
all processes are under cgroups. Kswapd is the only hope here which
however has a low efficiency of get_scan_count. I would like to have
kswapd work as direct reclaim in 2nd round which will have
protection=memory.min.
>
> --
> Michal Hocko
> SUSE Labs
next prev parent reply other threads:[~2021-10-27 9:20 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-10-27 7:01 [RFC PATCH] mm: have kswapd only reclaiming use min protection on memcg Huangzhaoyang
2021-10-27 7:20 ` Michal Hocko
2021-10-27 7:46 ` Zhaoyang Huang
2021-10-27 8:26 ` Michal Hocko
2021-10-27 9:19 ` Zhaoyang Huang [this message]
2021-10-27 11:52 ` Michal Hocko
2021-10-27 12:05 ` Zhaoyang Huang
2021-10-27 12:31 ` Michal Hocko
2021-10-28 0:45 ` Zhaoyang Huang
2021-10-28 2:04 ` Chris Down
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