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

Oscar Salvador
2022-09-01T04:53:04Z

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

Thanks

--
Oscar Salvador
SUSE Labs