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 16C3FC6FA8B for ; Mon, 5 Sep 2022 01:33:17 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235259AbiIEBdP (ORCPT ); Sun, 4 Sep 2022 21:33:15 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:43098 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229702AbiIEBdN (ORCPT ); Sun, 4 Sep 2022 21:33:13 -0400 Received: from mail-io1-xd31.google.com (mail-io1-xd31.google.com [IPv6:2607:f8b0:4864:20::d31]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DFFCF1EED1 for ; Sun, 4 Sep 2022 18:33:10 -0700 (PDT) Received: by mail-io1-xd31.google.com with SMTP id q81so5869171iod.9 for ; Sun, 04 Sep 2022 18:33:10 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date; bh=2RluQjqzTIUHmUhPkFaAucreOiCVZIKJVjpKNDHkTVI=; b=Q2SFjmrk55zpV9cBG3THFMLDJmuoc/8nrQ9p1qSD4f3cKratTElhXWpwlJpzLyLGdB dUdJn77SvWYU1bP95CNfftS8y/vUZXmtUUk048r8ICfLieWVmDGDmUW5u9pFn0Wimb2+ fjqU5NekUrHLRJIhO6WL/TlQwCGPS6j156hXfsaJx7lHdSgwEnbb8DWRFk8q7xjioT1t iG+0L8yNs39bpjd/CsZ4HREZ9tLgN3o/zOan5zEv/n3CDSIzOP4LnKLk4WpSk4BU0yEP 4AYwp1478Pf1dFxHmYXmnh+61qZlMLJPPjkGYHj5zdiNAcoW1tZU++xE8S7Db8in70AK L7BQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date; bh=2RluQjqzTIUHmUhPkFaAucreOiCVZIKJVjpKNDHkTVI=; b=oBBw5Sc3DtHrrIz/X379CgI9fgS+OoA1+0OzkX6jp7Eh+hwTmbMiiWT19f0UQt1+0M TLwLsqHKiJ9uwRCBTkR6A7+XQz355J92jqxwv4i0xBa0Lz70blXzev1qvT/CsJVi4n8N XP5wnG3QqmFXNEhW/2GDcWA3dr9qnvxidaonNzm6rTfsJF5tCXlKsdj5azrC22fDgIzo kP1PQe8EBMbkJypDop0oAnpf3gTNLsw50fs8W7WG1nEdVAO9THPmf2Gw63Y0BMsM9yW6 YEg/2kcEW00XSAZYV8q/NWY+dM09Rfypj6vgmjQj91WsST4msIy48AxfwFy7mctnUwor qWKw== X-Gm-Message-State: ACgBeo2LH73F8g/7O0v0Z3f3HghuNu49TsHkuX4xWi9CjrT7V9VtXKDz dVu7QAevfR707ceJ3BkcBCnOfqy7RwVrV3d2H7CgSg== X-Google-Smtp-Source: AA6agR5tFRVsPv1w5HQVwvNXMwt9PQzl6OY2wrpjmNL5au6axj2vXUaHdVOAmgfDNm2JaHEXPkzVG4QoN+UeQErwqKQ= X-Received: by 2002:a02:7b19:0:b0:34a:74d:118 with SMTP id q25-20020a027b19000000b0034a074d0118mr23960434jac.62.1662341590010; Sun, 04 Sep 2022 18:33:10 -0700 (PDT) MIME-Version: 1.0 References: <20220830214919.53220-1-surenb@google.com> <20220831084230.3ti3vitrzhzsu3fs@moria.home.lan> <20220831101948.f3etturccmp5ovkl@suse.de> <20220831190154.qdlsxfamans3ya5j@moria.home.lan> In-Reply-To: From: Suren Baghdasaryan Date: Sun, 4 Sep 2022 18:32:58 -0700 Message-ID: Subject: Re: [RFC PATCH 00/30] Code tagging framework and applications To: Michal Hocko Cc: Kent Overstreet , Mel Gorman , Peter Zijlstra , Andrew Morton , Vlastimil Babka , Johannes Weiner , Roman Gushchin , Davidlohr Bueso , Matthew Wilcox , "Liam R. Howlett" , David Vernet , Juri Lelli , Laurent Dufour , Peter Xu , David Hildenbrand , Jens Axboe , mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org, changbin.du@intel.com, ytcoode@gmail.com, Vincent Guittot , Dietmar Eggemann , Steven Rostedt , Benjamin Segall , Daniel Bristot de Oliveira , Valentin Schneider , Christopher Lameter , Pekka Enberg , Joonsoo Kim , 42.hyeyoo@gmail.com, Alexander Potapenko , Marco Elver , Dmitry Vyukov , Shakeel Butt , Muchun Song , arnd@arndb.de, jbaron@akamai.com, David Rientjes , Minchan Kim , Kalesh Singh , kernel-team , linux-mm , 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, LKML Content-Type: text/plain; charset="UTF-8" Precedence: bulk List-ID: X-Mailing-List: io-uring@vger.kernel.org On Thu, Sep 1, 2022 at 12:15 PM Michal Hocko wrote: > > On Thu 01-09-22 08:33:19, Suren Baghdasaryan wrote: > > On Thu, Sep 1, 2022 at 12:18 AM Michal Hocko wrote: > [...] > > > So I find Peter's question completely appropriate while your response to > > > that not so much! Maybe ftrace is not the right tool for the intented > > > job. Maybe there are other ways and it would be really great to show > > > that those have been evaluated and they are not suitable for a), b) and > > > c) reasons. > > > > That's fair. > > For memory tracking I looked into using kmemleak and page_owner which > > can't match the required functionality at an overhead acceptable for > > production and pre-production testing environments. > > Being more specific would be really helpful. Especially when your cover > letter suggests that you rely on page_owner/memcg metadata as well to > match allocation and their freeing parts. > > > traces + BPF I > > haven't evaluated myself but heard from other members of my team who > > tried using that in production environment with poor results. I'll try > > to get more specific information on that. > > That would be helpful as well. > > > > E.g. Oscar has been working on extending page_ext to track number of > > > allocations for specific calltrace[1]. Is this 1:1 replacement? No! But > > > it can help in environments where page_ext can be enabled and it is > > > completely non-intrusive to the MM code. > > > > Thanks for pointing out this work. I'll need to review and maybe > > profile it before making any claims. > > > > > > > > If the page_ext overhead is not desirable/acceptable then I am sure > > > there are other options. E.g. kprobes/LivePatching framework can hook > > > into functions and alter their behavior. So why not use that for data > > > collection? Has this been evaluated at all? > > > > I'm not sure how I can hook into say alloc_pages() to find out where > > it was called from without capturing the call stack (which would > > introduce an overhead at every allocation). Would love to discuss this > > or other alternatives if they can be done with low enough overhead. > > Yes, tracking back the call trace would be really needed. The question > is whether this is really prohibitively expensive. How much overhead are > we talking about? There is no free lunch here, really. You either have > the overhead during runtime when the feature is used or on the source > code level for all the future development (with a maze of macros and > wrappers). As promised, I profiled a simple code that repeatedly makes 10 allocations/frees in a loop and measured overheads of code tagging, call stack capturing and tracing+BPF for page and slab allocations. Summary: Page allocations (overheads are compared to get_free_pages() duration): 6.8% Codetag counter manipulations (__lazy_percpu_counter_add + __alloc_tag_add) 8.8% lookup_page_ext 1237% call stack capture 139% tracepoint with attached empty BPF program Slab allocations (overheads are compared to __kmalloc() duration): With CONFIG_MEMCG_KMEM=y 39% Codetag counter manipulations(__lazy_percpu_counter_add + __alloc_tag_add) 55% get_slab_tag_ref 3.9% __ksize 3027% call stack capture 397% tracepoint with attached empty BPF program With CONFIG_MEMCG_KMEM=n 26% Codetag counter manipulation(__lazy_percpu_counter_add + __alloc_tag_add) 72% get_slab_tag_ref 7.4% __ksize 2789% call stack capture 345% tracepoint with attached empty BPF program Details: _get_free_pages is used as page allocation duration baseline __kmalloc is used as slab allocation duration baseline 1. Profile with instrumented page allocator |--50.13%--my__get_free_page | | | |--38.99%--_get_free_pages | | | | | |--34.75%--__alloc_pages | | | | | | | |--27.59%--get_page_from_freelist | | | | | --3.98%--_alloc_pages | | | | | --0.53%--policy_node | | | |--3.45%--lookup_page_ext | | | |--1.59%--__lazy_percpu_counter_add | | | | | --0.80%--pcpu_alloc | | memset_orig | | | --1.06%--__alloc_tag_add | | | --0.80%--__lazy_percpu_counter_add | |--35.28%--free_unref_page | | | |--23.08%--_raw_spin_unlock_irqrestore | | | |--2.39%--preempt_count_add | | | | | --0.80%--in_lock_functions | | | |--1.59%--free_pcp_prepare | | | |--1.33%--preempt_count_sub | | | --0.80%--check_preemption_disabled | |--4.24%--__free_pages | --1.59%--free_pages 2. Profile with non-instrumented page allocator and call stack capturing |--84.18%--my__get_free_page | | | --83.91%--stack_depot_capture_stack | | | |--77.99%--stack_trace_save | | | | | --77.53%--arch_stack_walk | | | | | |--37.17%--unwind_next_frame | | | | | | | |--8.44%--__orc_find | | | | | | |--10.57%-stack_trace_consume_entry | | | | | --9.64%--unwind_get_return_address | | | --5.78%--__stack_depot_save | |--6.78%--__get_free_pages | | | |--5.85%--__alloc_pages | | | | | --3.86%--get_page_from_freelist | | | | | --1.33%--_raw_spin_unlock_irqrestore | | | --0.80%--alloc_pages | |--5.19%--free_unref_page | | | |--2.73%--_raw_spin_unlock_irqrestore | | | --0.60%--free_pcp_prepare | --0.73%--__free_pages 3. Profile with non-instrumented page allocator and BPF attached to tracepoint |--42.42%--my__get_free_page | | | --38.53%--perf_trace_kmem_alloc | | | |--25.76%--perf_trace_run_bpf_submit | | | | | |--21.86%--trace_call_bpf | | | | | | | |--4.76%--migrate_enable | | | | | | | |--4.55%--migrate_disable | | | | | | | |--3.03%--check_preemption_disabled | | | | | | | |--0.65%--__this_cpu_preempt_check | | | | | | | --0.65%--__rcu_read_unlock | | | | | --0.87%--check_preemption_disabled | | | |--8.01%--perf_trace_buf_alloc | | | | | |--3.68%--perf_swevent_get_recursion_context | | | | | | | --0.87%--check_preemption_disabled | | | | | --1.30%--check_preemption_disabled | | | --0.87%--check_preemption_disabled | |--27.71%--__get_free_pages | | | |--23.38%--__alloc_pages | | | | | --17.75%--get_page_from_freelist | | | | | |--8.66%--_raw_spin_unlock_irqrestore | | | | | | | --1.95%--preempt_count_sub | | | | | --1.08%--preempt_count_add | | | --4.33%--alloc_pages | | | |--0.87%--policy_node | | | --0.65%--policy_nodemask | |--15.37%--free_unref_page | | | |--6.71%--_raw_spin_unlock_irqrestore | | | |--1.52%--check_preemption_disabled | | | |--0.65%--free_pcp_prepare | | | --0.65%--preempt_count_add |--4.98%--__free_pages 4. Profile with instrumented slab allocator CONFIG_MEMCG_KMEM=y |--51.28%--my__get_free_page | | | |--21.79%--__kmalloc | | | | | |--3.42%--memcg_slab_post_alloc_hook | | | | | |--1.71%--kmalloc_slab | | | | | --0.85%--should_failslab | | | |--11.97%--get_slab_tag_ref | | | |--5.56%--__alloc_tag_add | | | | | --2.56%--__lazy_percpu_counter_add | | | |--2.99%--__lazy_percpu_counter_add | | | --0.85%--__ksize | --35.90%--kfree | |--13.68%--get_slab_tag_ref | |--6.41%--__alloc_tag_sub | | | --4.70%--__lazy_percpu_counter_add | --2.14%--__ksize 5. Profile with non-instrumented slab allocator and call stack capturing CONFIG_MEMCG_KMEM=y |--91.50%--my__get_free_page | | | --91.13%--stack_depot_capture_stack | | | |--85.48%--stack_trace_save | | | | | --85.12%--arch_stack_walk | | | | | |--40.54%--unwind_next_frame | | | | | |--14.30%--__unwind_start | | | | | |--11.95%-unwind_get_return_address | | | | | --10.48%-stack_trace_consume_entry | | | --4.99%--__stack_depot_save | | | --0.66%--filter_irq_stacks | |--3.01%--__kmalloc | |--2.05%--kfree 6. Profile with non-instrumented slab allocator and BPF attached to a tracepoint CONFIG_MEMCG_KMEM=y |--72.39%--__kmalloc | | | |--57.84%--perf_trace_kmem_alloc | | | | | |--38.06%--perf_trace_run_bpf_submit | | | | | | | --33.96%--trace_call_bpf | | | | | | | |--10.07%--migrate_disable | | | | | | | |--4.85%--migrate_enable | | | | | | | |--4.10%--check_preemption_disabled | | | | | | | |--1.87%--__rcu_read_unlock | | | | | | | --0.75%--__rcu_read_lock | | | | | --9.70%--perf_trace_buf_alloc | | | | | |--2.99%--perf_swevent_get_recursion_context | | | | | |--1.12%--check_preemption_disabled | | | | | --0.75%--debug_smp_processor_id | | | |--2.24%--kmalloc_slab | | | |--1.49%--memcg_slab_post_alloc_hook | | | --1.12%--__cond_resched | |--7.84%--kfree 7. Profile with instrumented slab allocator CONFIG_MEMCG_KMEM=n |--49.39%--my__get_free_page | | | |--22.04%--__kmalloc | | | | | |--3.27%--kmalloc_slab | | | | | --0.82%--asm_sysvec_apic_timer_interrupt | | sysvec_apic_timer_interrupt | | __irq_exit_rcu | | __softirqentry_text_start | | | |--15.92%--get_slab_tag_ref | | | |--3.27%--__alloc_tag_add | | | | | --2.04%--__lazy_percpu_counter_add | | | --2.45%--__lazy_percpu_counter_add | |--35.51%--kfree | | | |--13.88%--get_slab_tag_ref | | | |--11.84%--__alloc_tag_sub | | | | | --5.31%--__lazy_percpu_counter_add | | | --1.63%--__ksize 8. Profile with non-instrumented slab allocator and call stack capturing CONFIG_MEMCG_KMEM=n |--91.70%--my__get_free_page | | | --91.48%--stack_depot_capture_stack | | | |--85.29%--stack_trace_save | | | | | --85.07%--arch_stack_walk | | | | | |--45.23%--unwind_next_frame | | | | | |--12.89%--__unwind_start | | | | | |--10.20%-unwind_get_return_address | | | | | --10.12%-stack_trace_consume_entry | | | --5.75%--__stack_depot_save | | | --0.87%--filter_irq_stacks | |--3.28%--__kmalloc | --1.89%--kfree 9. Profile with non-instrumented slab allocator and BPF attached to a tracepoint CONFIG_MEMCG_KMEM=n |--71.65%--__kmalloc | | | |--55.56%--perf_trace_kmem_alloc | | | | | |--38.31%--perf_trace_run_bpf_submit | | | | | | | |--31.80%--trace_call_bpf | | | | | | | | | |--9.96%--migrate_enable | | | | | | | | | |--4.98%--migrate_disable | | | | | | | | | |--1.92%--check_preemption_disabled | | | | | | | | | |--1.92%--__rcu_read_unlock | | | | | | | | | --1.15%--__rcu_read_lock | | | | | | | --0.77%--check_preemption_disabled | | | | | --11.11%--perf_trace_buf_alloc | | | | | --4.98%--perf_swevent_get_recursion_context | | | | | --1.53%--check_preemption_disabled | | | |--2.68%--kmalloc_slab | | | --1.15%--__cond_resched | --9.58%--kfree > > Thanks! > -- > Michal Hocko > SUSE Labs