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 93661C3DA6B for ; Wed, 31 Aug 2022 10:47:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230073AbiHaKri (ORCPT ); Wed, 31 Aug 2022 06:47:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42356 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229611AbiHaKrg (ORCPT ); Wed, 31 Aug 2022 06:47:36 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id D8F13C9E81; Wed, 31 Aug 2022 03:47:35 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 136B61F9EB; Wed, 31 Aug 2022 10:47:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.com; s=susede1; t=1661942854; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=aUzDVspS6J0BJDe/V//gF5+N5LyMdFoI/5xdVcYfQNM=; b=hx3jXnZOgBCn3O0WO5J/LlyY4IiYG5gqZXnpoO+NYEqMohd/U77AF74Flu0p9pljpDRGno sMp8XYRkBw5hCVEmHJBlQYPVx0BIUes6WerAjPMj8ahTkMIBlfO+J5Y3xm3LewxX5zGMbB lhArCO8EcmvjMet8opjkPdqbWHMxN8I= Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id DA44113A7C; Wed, 31 Aug 2022 10:47:33 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id 3HtANUU8D2PVawAAMHmgww (envelope-from ); Wed, 31 Aug 2022 10:47:33 +0000 Date: Wed, 31 Aug 2022 12:47:32 +0200 From: Michal Hocko To: Mel Gorman Cc: Kent Overstreet , Peter Zijlstra , Suren Baghdasaryan , akpm@linux-foundation.org, vbabka@suse.cz, hannes@cmpxchg.org, roman.gushchin@linux.dev, dave@stgolabs.net, willy@infradead.org, liam.howlett@oracle.com, void@manifault.com, juri.lelli@redhat.com, ldufour@linux.ibm.com, peterx@redhat.com, david@redhat.com, axboe@kernel.dk, mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, changbin.du@intel.com, ytcoode@gmail.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, bristot@redhat.com, vschneid@redhat.com, cl@linux.com, penberg@kernel.org, iamjoonsoo.kim@lge.com, 42.hyeyoo@gmail.com, glider@google.com, elver@google.com, dvyukov@google.com, shakeelb@google.com, songmuchun@bytedance.com, arnd@arndb.de, jbaron@akamai.com, rientjes@google.com, minchan@google.com, kaleshsingh@google.com, kernel-team@android.com, linux-mm@kvack.org, iommu@lists.linux.dev, kasan-dev@googlegroups.com, io-uring@vger.kernel.org, linux-arch@vger.kernel.org, xen-devel@lists.xenproject.org, linux-bcache@vger.kernel.org, linux-modules@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [RFC PATCH 00/30] Code tagging framework and applications Message-ID: References: <20220830214919.53220-1-surenb@google.com> <20220831084230.3ti3vitrzhzsu3fs@moria.home.lan> <20220831101948.f3etturccmp5ovkl@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220831101948.f3etturccmp5ovkl@suse.de> Precedence: bulk List-ID: X-Mailing-List: linux-bcache@vger.kernel.org On Wed 31-08-22 11:19:48, Mel Gorman wrote: > On Wed, Aug 31, 2022 at 04:42:30AM -0400, Kent Overstreet wrote: > > On Wed, Aug 31, 2022 at 09:38:27AM +0200, Peter Zijlstra wrote: > > > On Tue, Aug 30, 2022 at 02:48:49PM -0700, Suren Baghdasaryan wrote: > > > > =========================== > > > > Code tagging framework > > > > =========================== > > > > Code tag is a structure identifying a specific location in the source code > > > > which is generated at compile time and can be embedded in an application- > > > > specific structure. Several applications of code tagging are included in > > > > this RFC, such as memory allocation tracking, dynamic fault injection, > > > > latency tracking and improved error code reporting. > > > > Basically, it takes the old trick of "define a special elf section for > > > > objects of a given type so that we can iterate over them at runtime" and > > > > creates a proper library for it. > > > > > > I might be super dense this morning, but what!? I've skimmed through the > > > set and I don't think I get it. > > > > > > What does this provide that ftrace/kprobes don't already allow? > > > > You're kidding, right? > > It's a valid question. From the description, it main addition that would > be hard to do with ftrace or probes is catching where an error code is > returned. A secondary addition would be catching all historical state and > not just state since the tracing started. > > It's also unclear *who* would enable this. It looks like it would mostly > have value during the development stage of an embedded platform to track > kernel memory usage on a per-application basis in an environment where it > may be difficult to setup tracing and tracking. Would it ever be enabled > in production? Would a distribution ever enable this? If it's enabled, any > overhead cannot be disabled/enabled at run or boot time so anyone enabling > this would carry the cost without never necessarily consuming the data. > > It might be an ease-of-use thing. Gathering the information from traces > is tricky and would need combining multiple different elements and that > is development effort but not impossible. > > Whatever asking for an explanation as to why equivalent functionality > cannot not be created from ftrace/kprobe/eBPF/whatever is reasonable. Fully agreed and this is especially true for a change this size 77 files changed, 3406 insertions(+), 703 deletions(-) -- Michal Hocko SUSE Labs