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 <CAJD7tkZh=M58Avfwx_D+UEXy6mm18Zx_hVKn8Gb8-+8-JQQfWw@mail.gmail.com> <20240202224117.GA341862@cmpxchg.org>
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From: "T.J. Mercier" <tjmercier@google.com>
Date: Fri, 2 Feb 2024 14:51:24 -0800
Message-ID: <CABdmKX3hqxd_0n1Rr=SL8V2HbsjjcCUQaGCQ85E72OHmZp-O_w@mail.gmail.com>
Subject: Re: [PATCH v2] mm: memcg: Use larger batches for proactive reclaim
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Yosry Ahmed <yosryahmed@google.com>, Michal Hocko <mhocko@kernel.org>, 
	Roman Gushchin <roman.gushchin@linux.dev>, Shakeel Butt <shakeelb@google.com>, 
	Muchun Song <muchun.song@linux.dev>, Andrew Morton <akpm@linux-foundation.org>, 
	Efly Young <yangyifei03@kuaishou.com>, android-mm@google.com, yuzhao@google.com, 
	mkoutny@suse.com, cgroups@vger.kernel.org, linux-mm@kvack.org, 
	linux-kernel@vger.kernel.org
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On Fri, Feb 2, 2024 at 2:41=E2=80=AFPM Johannes Weiner <hannes@cmpxchg.org>=
 wrote:
>
> On Fri, Feb 02, 2024 at 02:13:20PM -0800, Yosry Ahmed wrote:
> > On Fri, Feb 2, 2024 at 2:10=E2=80=AFPM T.J. Mercier <tjmercier@google.c=
om> wrote:
> > > @@ -6965,6 +6965,9 @@ static ssize_t memory_reclaim(struct kernfs_ope=
n_file *of, char *buf,
> > >         while (nr_reclaimed < nr_to_reclaim) {
> > >                 unsigned long reclaimed;
> > >
> > > +               /* Will converge on zero, but reclaim enforces a mini=
mum */
> > > +               unsigned long batch_size =3D (nr_to_reclaim - nr_recl=
aimed) / 4;
> > > +
> > >                 if (signal_pending(current))
> > >                         return -EINTR;
> > >
> > > @@ -6977,7 +6980,7 @@ static ssize_t memory_reclaim(struct kernfs_ope=
n_file *of, char *buf,
> > >                         lru_add_drain_all();
> > >
> > >                 reclaimed =3D try_to_free_mem_cgroup_pages(memcg,
> > > -                                       min(nr_to_reclaim - nr_reclai=
med, SWAP_CLUSTER_MAX),
> > > +                                       batch_size,
> > >                                         GFP_KERNEL, reclaim_options);
> >
> > I think the above two lines should now fit into one.
>
> Yeah might as well compact that again. The newline in the declarations
> is a bit unusual for this codebase as well, and puts the comment sort
> of away from the "reclaim" it refers to. This?
>
>                 /* Will converge on zero, but reclaim enforces a minimum =
*/
>                 batch_size =3D (nr_to_reclaim - nr_reclaimed) / 4;
>
>                 reclaimed =3D try_to_free_mem_cgroup_pages(memcg, batch_s=
ize,
>                                         GFP_KERNEL, reclaim_options);
>
> But agreed, it's all just nitpickety nickpicking. :)
>
> Acked-by: Johannes Weiner <hannes@cmpxchg.org>

-std=3Dgnu11 to the rescue

+               /* Will converge on zero, but reclaim enforces a minimum */
+               unsigned long batch_size =3D (nr_to_reclaim - nr_reclaimed)=
 / 4;
                reclaimed =3D try_to_free_mem_cgroup_pages(memcg,
-                                       min(nr_to_reclaim -
nr_reclaimed, SWAP_CLUSTER_MAX),
+                                       batch_size,
                                        GFP_KERNEL, reclaim_options);