linux-kernel - Re: [PATCH v3 00/35] Memory allocation profiling

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Date: Wed, 14 Feb 2024 10:01:14 -0500
From: Kent Overstreet <kent.overstreet@...ux.dev>
To: Michal Hocko <mhocko@...e.com>
Cc: Johannes Weiner <hannes@...xchg.org>, 
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Subject: Re: [PATCH v3 00/35] Memory allocation profiling

On Wed, Feb 14, 2024 at 03:46:33PM +0100, Michal Hocko wrote:
> On Wed 14-02-24 01:20:20, Johannes Weiner wrote:
> [...]
> > I agree we should discuss how the annotations are implemented on a
> > technical basis, but my take is that we need something like this.
> 
> I do not think there is any disagreement on usefulness of a better
> memory allocation tracking. At least for me the primary problem is the
> implementation. At LFSMM last year we have heard that existing tracing
> infrastructure hasn't really been explored much. Cover letter doesn't
> really talk much about those alternatives so it is really hard to
> evaluate whether the proposed solution is indeed our best way to
> approach this.

Michal, we covered this before.

To do this with tracing you'd have to build up data structures
separately, in userspace, that would mirror the allocator's data
structures; you would have to track every single allocation so that you
could match up the free event to the place it was allocated.

Even if it could be built, which I doubt, it'd be completely non viable
because the performance would be terrible.

Like I said, we covered all this before; if you're going to spend so
much time on these threads you really should be making a better attempt
at keeping up with what's been talked about.