linux-kernel - Re: [PATCH v2 17/18] lib/stackdepot: various comments clean-ups

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Message-ID: <CAG_fn=VM34NfOhir_3y86=SKxZ=PqbC3DFuFVAmLEYp8Z9Ax3A@mail.gmail.com>
Date:   Mon, 13 Feb 2023 14:26:10 +0100
From:   Alexander Potapenko <glider@...gle.com>
To:     andrey.konovalov@...ux.dev
Cc:     Marco Elver <elver@...gle.com>,
        Andrey Konovalov <andreyknvl@...il.com>,
        Vlastimil Babka <vbabka@...e.cz>, kasan-dev@...glegroups.com,
        Evgenii Stepanov <eugenis@...gle.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org,
        Andrey Konovalov <andreyknvl@...gle.com>
Subject: Re: [PATCH v2 17/18] lib/stackdepot: various comments clean-ups

On Fri, Feb 10, 2023 at 10:18 PM <andrey.konovalov@...ux.dev> wrote:
>
> From: Andrey Konovalov <andreyknvl@...gle.com>
>
> Clean up comments in include/linux/stackdepot.h and lib/stackdepot.c:
>
> 1. Rework the initialization comment in stackdepot.h.
> 2. Rework the header comment in stackdepot.c.
> 3. Various clean-ups for other comments.
>
> Also adjust whitespaces for find_stack and depot_alloc_stack call sites.
>
> No functional changes.
>
> Signed-off-by: Andrey Konovalov <andreyknvl@...gle.com>
Reviewed-by: Alexander Potapenko <glider@...gle.com>

> - * Instead, stack depot maintains a hashtable of unique stacktraces. Since alloc
> - * and free stacks repeat a lot, we save about 100x space.
> - * Stacks are never removed from depot, so we store them contiguously one after
> - * another in a contiguous memory allocation.
> + * For example, KASAN needs to save allocation and free stack traces for each

s/free/deallocation, maybe? (Here and below)
> + * object. Storing two stack traces per object requires a lot of memory (e.g.
> + * SLUB_DEBUG needs 256 bytes per object for that). Since allocation and free
> + * stack traces often repeat, using stack depot allows to save about 100x space.