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[96.67.55.147]) by mx.google.com with ESMTPS id o3si2936644qvl.30.2019.01.28.12.03.32 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 28 Jan 2019 12:03:32 -0800 (PST) Received-SPF: pass (google.com: best guess record for domain of riel@shelob.surriel.com designates 96.67.55.147 as permitted sender) client-ip=96.67.55.147; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of riel@shelob.surriel.com designates 96.67.55.147 as permitted sender) smtp.mailfrom=riel@shelob.surriel.com Received: from imladris.surriel.com ([96.67.55.152]) by shelob.surriel.com with esmtpsa (TLSv1.2:ECDHE-RSA-AES256-GCM-SHA384:256) (Exim 4.91) (envelope-from ) id 1goD7w-0006yz-Lt; Mon, 28 Jan 2019 15:03:28 -0500 Message-ID: <8ddf2ea674711f373062f4e056dd14fb81c5a2fe.camel@surriel.com> Subject: Re: [PATCH] mm,slab,vmscan: accumulate gradual pressure on small slabs From: Rik van Riel To: Andrew Morton Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@fb.com, Johannes Weiner , Chris Mason , Roman Gushchin , Michal Hocko Date: Mon, 28 Jan 2019 15:03:28 -0500 In-Reply-To: <20190128115424.df3f4647023e9e43e75afe67@linux-foundation.org> References: <20190128143535.7767c397@imladris.surriel.com> <20190128115424.df3f4647023e9e43e75afe67@linux-foundation.org> Content-Type: multipart/signed; micalg="pgp-sha256"; protocol="application/pgp-signature"; boundary="=-nGE8UQknFPEiL8nfsYnb" X-Mailer: Evolution 3.28.5 (3.28.5-1.fc28) Mime-Version: 1.0 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: --=-nGE8UQknFPEiL8nfsYnb Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Mon, 2019-01-28 at 11:54 -0800, Andrew Morton wrote: > On Mon, 28 Jan 2019 14:35:35 -0500 Rik van Riel > wrote: >=20 > > /* > > * Make sure we apply some minimal pressure on default priority > > - * even on small cgroups. Stale objects are not only consuming > > memory > > + * even on small cgroups, by accumulating pressure across > > multiple > > + * slab shrinker runs. Stale objects are not only consuming > > memory > > * by themselves, but can also hold a reference to a dying > > cgroup, > > * preventing it from being reclaimed. A dying cgroup with all > > * corresponding structures like per-cpu stats and kmem caches > > * can be really big, so it may lead to a significant waste of > > memory. > > */ > > - delta =3D max_t(unsigned long long, delta, min(freeable, > > batch_size)); > > + if (!delta) { > > + shrinker->small_scan +=3D freeable; > > + > > + delta =3D shrinker->small_scan >> priority; > > + shrinker->small_scan -=3D delta << priority; > > + > > + delta *=3D 4; > > + do_div(delta, shrinker->seeks); >=20 > What prevents shrinker->small_scan from over- or underflowing over > time? We only go into this code path if delta >> DEF_PRIORITY is zero. That is, freeable is smaller than 4096. > I'll add this: > whitespace fixes, per Roman Awesome, thank you! --=20 All Rights Reversed. --=-nGE8UQknFPEiL8nfsYnb Content-Type: application/pgp-signature; name="signature.asc" Content-Description: This is a digitally signed message part Content-Transfer-Encoding: 7bit -----BEGIN PGP SIGNATURE----- iQEzBAABCAAdFiEEKR73pCCtJ5Xj3yADznnekoTE3oMFAlxPYBAACgkQznnekoTE 3oN05AgAngaeuhkjCHuyhq8zG04YT0jvQFZoWcNexTYi/rVLmxraUqdOJhpgIvFl YMidQJwFi1448jznIdXf3/dgyvbu5JI+JoyhwlfmLv8wyHGWo59AfSkCT8bAPKR5 qHFY0TQCoOM/QyIW5Qeew5iHjNxceZfLvXNQVlt02jPoR5ysBWC9mudPYHAcTggZ 4fH8MkS8ukd8ykvx+WbEoO8GzTQrqwcc8bvPsl+mq7I+H2V6J1JhzQON3BSYZnNG 1SWKuzYdAYP6pxUXYweEl2YkTm4KtNgcxLPF3T8h99Gwa1/Nb9SvWSp6oZB4s9UD SWeY7MLKfnBK5aox7F+ilHrcYJrMfw== =O2ss -----END PGP SIGNATURE----- --=-nGE8UQknFPEiL8nfsYnb--