linux-kernel - Re: [RFC PATCH 00/30] Code tagging framework and applications

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Date:   Wed, 31 Aug 2022 22:05:28 -0700
From:   Suren Baghdasaryan <surenb@...gle.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Kent Overstreet <kent.overstreet@...ux.dev>,
        Michal Hocko <mhocko@...e.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Roman Gushchin <roman.gushchin@...ux.dev>,
        Mel Gorman <mgorman@...e.de>,
        Davidlohr Bueso <dave@...olabs.net>,
        Matthew Wilcox <willy@...radead.org>,
        "Liam R. Howlett" <liam.howlett@...cle.com>,
        David Vernet <void@...ifault.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Juri Lelli <juri.lelli@...hat.com>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        Peter Xu <peterx@...hat.com>,
        David Hildenbrand <david@...hat.com>,
        Jens Axboe <axboe@...nel.dk>, mcgrof@...nel.org,
        masahiroy@...nel.org, nathan@...nel.org, ytcoode@...il.com,
        Vincent Guittot <vincent.guittot@...aro.org>,
        Dietmar Eggemann <dietmar.eggemann@....com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Benjamin Segall <bsegall@...gle.com>,
        Daniel Bristot de Oliveira <bristot@...hat.com>,
        Valentin Schneider <vschneid@...hat.com>,
        Christopher Lameter <cl@...ux.com>,
        Pekka Enberg <penberg@...nel.org>,
        Joonsoo Kim <iamjoonsoo.kim@....com>, 42.hyeyoo@...il.com,
        Alexander Potapenko <glider@...gle.com>,
        Marco Elver <elver@...gle.com>, dvyukov@...gle.com,
        Shakeel Butt <shakeelb@...gle.com>,
        Muchun Song <songmuchun@...edance.com>, arnd@...db.de,
        jbaron@...mai.com, David Rientjes <rientjes@...gle.com>,
        Minchan Kim <minchan@...gle.com>,
        Kalesh Singh <kaleshsingh@...gle.com>,
        kernel-team <kernel-team@...roid.com>,
        linux-mm <linux-mm@...ck.org>, iommu@...ts.linux.dev,
        kasan-dev@...glegroups.com, io-uring@...r.kernel.org,
        linux-arch@...r.kernel.org, xen-devel@...ts.xenproject.org,
        linux-bcache@...r.kernel.org, linux-modules@...r.kernel.org,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [RFC PATCH 00/30] Code tagging framework and applications

On Wed, Aug 31, 2022 at 9:52 PM Oscar Salvador <osalvador@...e.de> 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.
> >
> > ===========================
> > Memory allocation tracking
> > ===========================
> > The goal for using codetags for memory allocation tracking is to minimize
> > performance and memory overhead. By recording only the call count and
> > allocation size, the required operations are kept at the minimum while
> > collecting statistics for every allocation in the codebase. With that
> > information, if users are interested in mode detailed context for a
> > specific allocation, they can enable more in-depth context tracking,
> > which includes capturing the pid, tgid, task name, allocation size,
> > timestamp and call stack for every allocation at the specified code
> > location.
> > Memory allocation tracking is implemented in two parts:
> >
> > part1: instruments page and slab allocators to record call count and total
> > memory allocated at every allocation in the source code. Every time an
> > allocation is performed by an instrumented allocator, the codetag at that
> > location increments its call and size counters. Every time the memory is
> > freed these counters are decremented. To decrement the counters upon free,
> > allocated object needs a reference to its codetag. Page allocators use
> > page_ext to record this reference while slab allocators use memcg_data of
> > the slab page.
> > The data is exposed to the user space via a read-only debugfs file called
> > alloc_tags.
>
> Hi Suren,
>
> I just posted a patch [1] and reading through your changelog and seeing your PoC,
> I think we have some kind of overlap.
> My patchset aims to give you the stacktrace <-> relationship information and it is
> achieved by a little amount of extra code mostly in page_owner.c/ and lib/stackdepot.
>
> Of course, your works seems to be more complete wrt. the information you get.
>
> I CCed you in case you want to have a look
>
> [1] https://lkml.org/lkml/2022/9/1/36

Hi Oscar,
Thanks for the note. I'll take a look most likely on Friday and will
follow up with you.
Thanks,
Suren.

>
> Thanks
>
>
> --
> Oscar Salvador
> SUSE Labs