linux-kernel - Re: [PATCH 2/9] lib/ref_tracker: compact stacktraces before printing

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Date:   Fri, 18 Feb 2022 05:01:04 -0800
From:   Eric Dumazet <edumazet@...gle.com>
To:     Andrzej Hajda <andrzej.hajda@...el.com>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        intel-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
        netdev <netdev@...r.kernel.org>,
        Jani Nikula <jani.nikula@...ux.intel.com>,
        Daniel Vetter <daniel@...ll.ch>,
        Lucas De Marchi <lucas.demarchi@...el.com>,
        Chris Wilson <chris.p.wilson@...el.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>
Subject: Re: [PATCH 2/9] lib/ref_tracker: compact stacktraces before printing

On Fri, Feb 18, 2022 at 2:55 AM Andrzej Hajda <andrzej.hajda@...el.com> wrote:
>

> OK, could be faster and less invasive.
> Other solution would be keeping the array in dir and update in every
> tracker alloc/free, this way we avoid iteration over potentially big
> list, but it would cost memory and since printing is rather rare I am
> not sure if it is worth.

printing is extremely rare [1]

We want to use ref_tracker in production, we need to keep the fast
path as fast as possible ;)

[1] If you think about providing access to the traces from sysfs, we
might need to make sure we do not hold the dir spinlock
during the expensive generation of the output data.