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 C98B0C433EF for ; Wed, 1 Jun 2022 21:24:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S231521AbiFAVYF (ORCPT ); Wed, 1 Jun 2022 17:24:05 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:39814 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231539AbiFAVX4 (ORCPT ); Wed, 1 Jun 2022 17:23:56 -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 19B47121CD3 for ; Wed, 1 Jun 2022 14:23:54 -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 A97886137F for ; Wed, 1 Jun 2022 21:23:53 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C5328C385B8; Wed, 1 Jun 2022 21:23:52 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1654118633; bh=baI/1cZI79/wp6OfnaSzJG6jkPfaG7SAvX2xPJStV0U=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=S1JHdwp5rwuGpJRGBvPvtFKqIeTSaxNjhiQeKUhjBQ0l9XOrcbEdVMcGFelZSB8fr bR2+KBh0DUkUOw0zdTKPklwQvNK116WN2NT3TDNQCOPaQ6uNNkUNE8AuPddKmzkpu2 mlqDg99/N3K5r6hozbYudcjal27ZOi/rQWoSg1xI= Date: Wed, 1 Jun 2022 14:23:51 -0700 From: Andrew Morton To: Roman Gushchin Cc: linux-mm@kvack.org, Dave Chinner , linux-kernel@vger.kernel.org, Kent Overstreet , Hillf Danton , Christophe JAILLET , Muchun Song Subject: Re: [PATCH v5 6/6] mm: shrinkers: add scan interface for shrinker debugfs Message-Id: <20220601142351.5e04fea5586ca51898d8785f@linux-foundation.org> In-Reply-To: <20220601032227.4076670-7-roman.gushchin@linux.dev> References: <20220601032227.4076670-1-roman.gushchin@linux.dev> <20220601032227.4076670-7-roman.gushchin@linux.dev> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-redhat-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 31 May 2022 20:22:27 -0700 Roman Gushchin wrote: > Add a scan interface which allows to trigger scanning of a particular > shrinker and specify memcg and numa node. It's useful for testing, > debugging and profiling of a specific scan_objects() callback. > Unlike alternatives (creating a real memory pressure and dropping > caches via /proc/sys/vm/drop_caches) this interface allows to interact > with only one shrinker at once. Also, if a shrinker is misreporting > the number of objects (as some do), it doesn't affect scanning. > > .. > > --- a/mm/shrinker_debug.c > +++ b/mm/shrinker_debug.c > @@ -99,6 +99,78 @@ static int shrinker_debugfs_count_show(struct seq_file *m, void *v) > } > DEFINE_SHOW_ATTRIBUTE(shrinker_debugfs_count); > > +static int shrinker_debugfs_scan_open(struct inode *inode, struct file *file) > +{ > + file->private_data = inode->i_private; > + return nonseekable_open(inode, file); > +} > + > +static ssize_t shrinker_debugfs_scan_write(struct file *file, > + const char __user *buf, > + size_t size, loff_t *pos) > +{ > + struct shrinker *shrinker = file->private_data; > + unsigned long nr_to_scan = 0, ino; > + struct shrink_control sc = { > + .gfp_mask = GFP_KERNEL, > + }; > + struct mem_cgroup *memcg = NULL; > + int nid; > + char kbuf[72]; > + int read_len = size < (sizeof(kbuf) - 1) ? size : (sizeof(kbuf) - 1); size_t or ulong would be more appropriate. > + ssize_t ret; > + > + if (copy_from_user(kbuf, buf, read_len)) > + return -EFAULT; > + kbuf[read_len] = '\0'; > + > + if (sscanf(kbuf, "%lu %d %lu", &ino, &nid, &nr_to_scan) < 2) Was it intentional to permit more than three args? > + return -EINVAL; > + > + if (nid < 0 || nid >= nr_node_ids) > + return -EINVAL; > + > + if (nr_to_scan == 0) > + return size; > + > + if (shrinker->flags & SHRINKER_MEMCG_AWARE) { > + memcg = mem_cgroup_get_from_ino(ino); > + if (!memcg || IS_ERR(memcg)) > + return -ENOENT; > + > + if (!mem_cgroup_online(memcg)) { > + mem_cgroup_put(memcg); > + return -ENOENT; > + } > + } else if (ino != 0) { > + return -EINVAL; > + } > + > + ret = down_read_killable(&shrinker_rwsem); > + if (ret) { > + mem_cgroup_put(memcg); > + return ret; > + } > + > + sc.nid = nid; > + sc.memcg = memcg; > + sc.nr_to_scan = nr_to_scan; > + sc.nr_scanned = nr_to_scan; > + > + shrinker->scan_objects(shrinker, &sc); > + > + up_read(&shrinker_rwsem); > + mem_cgroup_put(memcg); > + > + return size; > +}