linux-kernel - Re: [PATCH v2] cma: introduce CMA_ALLOC

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Message-Id: <20230810095451.cada824810441ecc955e2b2e@linux-foundation.org>
Date:   Thu, 10 Aug 2023 09:54:51 -0700
From:   Andrew Morton <akpm@...ux-foundation.org>
To:     Bibek Kumar Patro <quic_bibekkum@...cinc.com>
Cc:     <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <quic_pkondeti@...cinc.com>, <quic_charante@...cinc.com>
Subject: Re: [PATCH v2] cma: introduce CMA_ALLOC_DEBUG config

On Wed, 9 Aug 2023 18:46:40 +0530 Bibek Kumar Patro <quic_bibekkum@...cinc.com> wrote:

> Currently enabling CONFIG_CMA_DEBUG enables DEBUG preprocessor macro.
> If DEBUG is defined, it's equivalent to a printk with KERN_DEBUG loglevel
> flooding the dmesg buffer with pr_debug prints from mm/cma driver and from
> included files as well. This results in excessive amount of CMA logging and
> also might distract the debug teams with unrelated KERN_DEBUG prints.One of
> the ways engineers currently tackle this problem is by passing loglevel=N
> though commandline to suppress KERN_DEBUG messages. This approach can
> sometimes become tiresome due to its repetitive nature.
> This patch proposes an alternative approach by introducing a simple new
> config CONFIG_CMA_ALLOC_DEBUG which only shows the cma bit allocation
> status in case of cma failure and do not enable DEBUG preprocessor macro
> from CONFIG_CMA_DEBUG avoiding excessive CMA logging from pr_debug.
> Engineers and tech teams seeking only for bitmap status in case of cma
> failure can use this simple config instead of worrying about changing
> the loglevel or trying other similar workarounds.

Would it be better to control this at runtime?  With a /proc or /sys tunable?