From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3F37C433EF for ; Mon, 18 Apr 2022 09:27:47 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B603F8D000C; Mon, 18 Apr 2022 05:27:46 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B106A8D0007; Mon, 18 Apr 2022 05:27:46 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9FF5B8D000C; Mon, 18 Apr 2022 05:27:46 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (relay.hostedemail.com [64.99.140.28]) by kanga.kvack.org (Postfix) with ESMTP id 91C3F8D0007 for ; Mon, 18 Apr 2022 05:27:46 -0400 (EDT) Received: from smtpin06.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay06.hostedemail.com (Postfix) with ESMTP id 6775F24663 for ; Mon, 18 Apr 2022 09:27:46 +0000 (UTC) X-FDA: 79369472532.06.4734751 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf25.hostedemail.com (Postfix) with ESMTP id DA339A0009 for ; Mon, 18 Apr 2022 09:27:45 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 0A54F61198; Mon, 18 Apr 2022 09:27:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 750EBC385A7; Mon, 18 Apr 2022 09:27:41 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1650274064; bh=78ipSubuEt83d9OlB0v+oZf6e8ais0MrE8bFB7G1RcQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=n52Vfu1vt31Ptm88LVO38DixE0LCJ7EYKQm/gUzeh5vUnwQW9/qtX7WQe+ZadYcVv 7uASQ1/Whmw9pXnPeYwyux3ZhqL21wP/Lp2nFtmh3iPxSvGbgzS6kjweeV8eZ8fXWz evtljKZda8KHeAJCRvSGV8u8KbO0B7OwoPeuGz6rRj2yh75LB/1EJKUKlWwLy9AV5U nh7gKT5h0FOT6nUcXLlmWPS448WUO96JBBj/APdxIt5HEc7GIK+H626OkFHgU01bfb p/+aVFuXvXP7kk1hnR6epH7Mm6Mp588TpwWG3C4SBgLV8hOtFepmzyj0k41QbmvwCg HwEo538L2X7Cw== Date: Mon, 18 Apr 2022 12:27:36 +0300 From: Mike Rapoport To: Roman Gushchin Cc: linux-mm@kvack.org, Andrew Morton , Dave Chinner , linux-kernel@vger.kernel.org, Johannes Weiner , Michal Hocko , Shakeel Butt , Yang Shi Subject: Re: [PATCH rfc 0/5] mm: introduce shrinker sysfs interface Message-ID: References: <20220416002756.4087977-1-roman.gushchin@linux.dev> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220416002756.4087977-1-roman.gushchin@linux.dev> Authentication-Results: imf25.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=n52Vfu1v; dmarc=pass (policy=none) header.from=kernel.org; spf=pass (imf25.hostedemail.com: domain of rppt@kernel.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=rppt@kernel.org X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: DA339A0009 X-Stat-Signature: ex1jed7e3p9xzfj3br6ihi8jr91oszc3 X-HE-Tag: 1650274065-286924 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 Fri, Apr 15, 2022 at 05:27:51PM -0700, Roman Gushchin wrote: > There are 50+ different shrinkers in the kernel, many with their own bells and > whistles. Under the memory pressure the kernel applies some pressure on each of > them in the order of which they were created/registered in the system. Some > of them can contain only few objects, some can be quite large. Some can be > effective at reclaiming memory, some not. > > The only existing debugging mechanism is a couple of tracepoints in > do_shrink_slab(): mm_shrink_slab_start and mm_shrink_slab_end. They aren't > covering everything though: shrinkers which report 0 objects will never show up, > there is no support for memcg-aware shrinkers. Shrinkers are identified by their > scan function, which is not always enough (e.g. hard to guess which super > block's shrinker it is having only "super_cache_scan"). They are a passive > mechanism: there is no way to call into counting and scanning of an individual > shrinker and profile it. > > To provide a better visibility and debug options for memory shrinkers > this patchset introduces a /sys/kernel/shrinker interface, to some extent > similar to /sys/kernel/slab. Wouldn't debugfs better fit the purpose of shrinker debugging? -- Sincerely yours, Mike.