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[198.145.29.99]) by mx.google.com with ESMTPS id j100si3053145pje.52.2019.07.02.14.33.41 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Tue, 02 Jul 2019 14:33:42 -0700 (PDT) Received-SPF: pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) client-ip=198.145.29.99; Authentication-Results: mx.google.com; dkim=pass header.i=@kernel.org header.s=default header.b=RBa6CBZo; spf=pass (google.com: domain of akpm@linux-foundation.org designates 198.145.29.99 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org Received: from akpm3.svl.corp.google.com (unknown [104.133.8.65]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id ED1AE218CA; Tue, 2 Jul 2019 21:33:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1562103221; bh=7BKwrn5ZR0EvyKBoBdw71Sjqy+1SUbMyW6AzU7/ufH4=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=RBa6CBZoD/h1b3spSkXt/s5mk4/LF71sNM0q6jPS2dnne68logM7RJmnQeYqnoPlk We4S37hoCXN1vJ/SylpXLdidWn8wQovBsN3zWD/thJwRlA5V0kPWzkSRUxdgTRtCMR lCSW1e94ZmkPHXhQYrDUGU4rHNsLYjp0UCC4jn8o= Date: Tue, 2 Jul 2019 14:33:40 -0700 From: Andrew Morton To: Waiman Long Cc: Christoph Lameter , Pekka Enberg , David Rientjes , Joonsoo Kim , Alexander Viro , Jonathan Corbet , Luis Chamberlain , Kees Cook , Johannes Weiner , Michal Hocko , Vladimir Davydov , linux-mm@kvack.org, linux-doc@vger.kernel.org, linux-fsdevel@vger.kernel.org, cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, Roman Gushchin , Shakeel Butt , Andrea Arcangeli Subject: Re: [PATCH] mm, slab: Extend slab/shrink to shrink all the memcg caches Message-Id: <20190702143340.715f771192721f60de1699d7@linux-foundation.org> In-Reply-To: <78879b79-1b8f-cdfd-d4fa-610afe5e5d48@redhat.com> References: <20190702183730.14461-1-longman@redhat.com> <20190702130318.39d187dc27dbdd9267788165@linux-foundation.org> <78879b79-1b8f-cdfd-d4fa-610afe5e5d48@redhat.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.32; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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: On Tue, 2 Jul 2019 16:44:24 -0400 Waiman Long wrote: > On 7/2/19 4:03 PM, Andrew Morton wrote: > > On Tue, 2 Jul 2019 14:37:30 -0400 Waiman Long wro= te: > > > >> Currently, a value of '1" is written to /sys/kernel/slab//shrink > >> file to shrink the slab by flushing all the per-cpu slabs and free > >> slabs in partial lists. This applies only to the root caches, though. > >> > >> Extends this capability by shrinking all the child memcg caches and > >> the root cache when a value of '2' is written to the shrink sysfs file. > > Why? > > > > Please fully describe the value of the proposed feature to or users.=20 > > Always. >=20 > Sure. Essentially, the sysfs shrink interface is not complete. It allows > the root cache to be shrunk, but not any of the memcg caches.=A0 But that doesn't describe anything of value. Who wants to use this, and why? How will it be used? What are the use-cases?