linux-kernel - Re: [PATCH 00/40] Memory allocation profiling

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Message-ID: <20230503122839.0d9934c5@gandalf.local.home>
Date:   Wed, 3 May 2023 12:28:39 -0400
From:   Steven Rostedt <rostedt@...dmis.org>
To:     Suren Baghdasaryan <surenb@...gle.com>
Cc:     Michal Hocko <mhocko@...e.com>, akpm@...ux-foundation.org,
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Subject: Re: [PATCH 00/40] Memory allocation profiling

On Wed, 3 May 2023 08:09:28 -0700
Suren Baghdasaryan <surenb@...gle.com> wrote:

> There is another issue, which I think can be solved in a smart way but
> will either affect performance or would require more memory. With the
> tracing approach we don't know beforehand how many individual
> allocation sites exist, so we have to allocate code tags (or similar
> structures for counting) at runtime vs compile time. We can be smart
> about it and allocate in batches or even preallocate more than we need
> beforehand but, as I said, it will require some kind of compromise.

This approach is actually quite common, especially since tagging every
instance is usually overkill, as if you trace function calls in a running
kernel, you will find that only a small percentage of the kernel ever
executes. It's possible that you will be allocating a lot of tags that will
never be used. If run time allocation is possible, that is usually the
better approach.

-- Steve