linux-kernel - Re: [PATCH] mm/cma: add an API to enable/disable concurrent memory allocation for the CMA

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Message-ID: <Z5h0-qtjQvhhLH6j@infradead.org>
Date: Mon, 27 Jan 2025 22:11:06 -0800
From: Christoph Hellwig <hch@...radead.org>
To: yangge1116@....com
Cc: akpm@...ux-foundation.org, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, stable@...r.kernel.org,
	21cnbao@...il.com, david@...hat.com, baolin.wang@...ux.alibaba.com,
	aisheng.dong@....com, liuzixing@...on.cn
Subject: Re: [PATCH] mm/cma: add an API to enable/disable concurrent memory
 allocation for the CMA

On Fri, Jan 24, 2025 at 07:21:27PM +0800, yangge1116@....com wrote:
> From: yangge <yangge1116@....com>
> 
> Commit 60a60e32cf91 ("Revert "mm/cma.c: remove redundant cma_mutex lock"")
> simply reverts to the original method of using the cma_mutex to ensure
> that alloc_contig_range() runs sequentially. This change was made to avoid
> concurrency allocation failures. However, it can negatively impact
> performance when concurrent allocation of CMA memory is required.
> 
> To address this issue, we could introduce an API for concurrency settings,
> allowing users to decide whether their CMA can perform concurrent memory
> allocations or not.
> 
> Fixes: 60a60e32cf91 ("Revert "mm/cma.c: remove redundant cma_mutex lock"")
> Signed-off-by: yangge <yangge1116@....com>
> Cc: <stable@...r.kernel.org>

Umm, you're adding new unused functions while not even reporting what
the problem is.  This looks sketchy as hell and surely is not a stable
candidate.