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

From: Suren Baghdasaryan <surenb@google.com>
To: Oscar Salvador <osalvador@suse.de>
Cc: Andrew Morton <akpm@linux-foundation.org>,
	Kent Overstreet <kent.overstreet@linux.dev>,
	Michal Hocko <mhocko@suse.com>, Vlastimil Babka <vbabka@suse.cz>,
	Johannes Weiner <hannes@cmpxchg.org>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Mel Gorman <mgorman@suse.de>, Davidlohr Bueso <dave@stgolabs.net>,
	Matthew Wilcox <willy@infradead.org>,
	"Liam R. Howlett" <liam.howlett@oracle.com>,
	David Vernet <void@manifault.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Juri Lelli <juri.lelli@redhat.com>,
	Laurent Dufour <ldufour@linux.ibm.com>,
	Peter Xu <peterx@redhat.com>,
	David Hildenbrand <david@redhat.com>,
	Jens Axboe <axboe@kernel.dk>,
	mcgrof@kernel.org, masahiroy@kernel.org, nathan@kernel.org,
	ytcoode@gmail.com, Vincent Guittot <vincent.guittot@linaro.org>,
	Dietmar Eggemann <dietmar.eggemann@arm.com>,
	Steven Rostedt <rostedt@goodmis.org>,
	Benjamin Segall <bsegall@google.com>,
	Daniel Bristot de Oliveira <bristot@redhat.com>,
	Valentin Schneider <vschneid@redhat.com>,
	Christopher Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	42.hyeyoo@gmail.com, Alexander Potapenko <glider@google.com>,
	Marco Elver <elver@google.com>,
	dvyukov@google.com, Shakeel Butt <shakeelb@google.com>,
	Muchun Song <songmuchun@bytedance.com>,
	arnd@arndb.de, jbaron@akamai.com,
	David Rientjes <rientjes@google.com>,
	Minchan Kim <minchan@google.com>,
	Kalesh Singh <kaleshsingh@google.com>,
	kernel-team <kernel-team@android.com>,
	linux-mm <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,
	LKML <linux-kernel@vger.kernel.org>
Subject: Re: [RFC PATCH 00/30] Code tagging framework and applications
Date: Wed, 31 Aug 2022 22:05:28 -0700	[thread overview]
Message-ID: <CAJuCfpGxB0z1V1Vau3bXF9eHZVHnANdA7keMzCLUK+_gN6+HeA@mail.gmail.com> (raw)
In-Reply-To: <YxA6pCu0YNIiXkHf@localhost.localdomain>

On Wed, Aug 31, 2022 at 9:52 PM Oscar Salvador <osalvador@suse.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