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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id DE8C8C433F5 for ; Mon, 18 Apr 2022 09:27:51 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S237505AbiDRJa1 (ORCPT ); Mon, 18 Apr 2022 05:30:27 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:49092 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S237497AbiDRJaX (ORCPT ); Mon, 18 Apr 2022 05:30:23 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 671AA15FEF for ; Mon, 18 Apr 2022 02:27:45 -0700 (PDT) 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 0635061178 for ; 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> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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.