linux-kernel - Re: [PATCH] sched_ext: Use kvzalloc for large exit

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Message-ID: <ad86c91d-f9a1-4d66-9cc0-efa6a17c77a0@igalia.com>
Date: Tue, 8 Apr 2025 10:19:09 +0900
From: Changwoo Min <changwoo@...lia.com>
To: Breno Leitao <leitao@...ian.org>, Tejun Heo <tj@...nel.org>,
 David Vernet <void@...ifault.com>, Andrea Righi <arighi@...dia.com>,
 Ingo Molnar <mingo@...hat.com>, Peter Zijlstra <peterz@...radead.org>,
 Juri Lelli <juri.lelli@...hat.com>,
 Vincent Guittot <vincent.guittot@...aro.org>,
 Dietmar Eggemann <dietmar.eggemann@....com>,
 Steven Rostedt <rostedt@...dmis.org>, Ben Segall <bsegall@...gle.com>,
 Mel Gorman <mgorman@...e.de>, Valentin Schneider <vschneid@...hat.com>
Cc: linux-kernel@...r.kernel.org, kernel-team@...a.com,
 stable@...r.kernel.org, Rik van Riel <riel@...riel.com>
Subject: Re: [PATCH] sched_ext: Use kvzalloc for large exit_dump allocation

Hi,

On 4/8/25 04:50, Breno Leitao wrote:
> Replace kzalloc with kvzalloc for the exit_dump buffer allocation, which
> can require large contiguous memory (up to order=9) depending on the
> implementation. This change prevents allocation failures by allowing the
> system to fall back to vmalloc when contiguous memory allocation fails.
> 
> Since this buffer is only used for debugging purposes, physical memory
> contiguity is not required, making vmalloc a suitable alternative.
> 
> Cc: stable@...r.kernel.org
> Fixes: 07814a9439a3b0 ("sched_ext: Print debug dump after an error exit")
> Suggested-by: Rik van Riel <riel@...riel.com>
> Signed-off-by: Breno Leitao <leitao@...ian.org>
> ---
>   kernel/sched/ext.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/kernel/sched/ext.c b/kernel/sched/ext.c
> index 66bcd40a28ca1..c82725f9b0559 100644
> --- a/kernel/sched/ext.c
> +++ b/kernel/sched/ext.c
> @@ -4639,7 +4639,7 @@ static struct scx_exit_info *alloc_exit_info(size_t exit_dump_len)
>   
>   	ei->bt = kcalloc(SCX_EXIT_BT_LEN, sizeof(ei->bt[0]), GFP_KERNEL);
>   	ei->msg = kzalloc(SCX_EXIT_MSG_LEN, GFP_KERNEL);
> -	ei->dump = kzalloc(exit_dump_len, GFP_KERNEL);
> +	ei->dump = kvzalloc(exit_dump_len, GFP_KERNEL);
>   
>   	if (!ei->bt || !ei->msg || !ei->dump) {
>   		free_exit_info(ei);
>

The change makes sense to me. But the kfree(ei->dump) in 
free_exit_info() also should be replaced with kvfree(ei->dump).

Regards,
Changwoo Min

> ---
> base-commit: 0af2f6be1b4281385b618cb86ad946eded089ac8
> change-id: 20250407-scx-11dbf94803c3
> 
> Best regards,