linux-kernel - Re: [patch V2 RESEND 3/6] perf/core: Split out VM accounting

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Message-ID: <3be7fd83-e209-49ec-8d81-ba6a60d4da94@lucifer.local>
Date: Mon, 11 Aug 2025 13:58:24 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: Thomas Gleixner <tglx@...utronix.de>
Cc: LKML <linux-kernel@...r.kernel.org>,
        Linus Torvalds <torvalds@...uxfoundation.org>,
        Peter Zijlstra <peterz@...radead.org>, Ingo Molnar <mingo@...nel.org>,
        Namhyung Kim <namhyung@...nel.org>,
        Arnaldo Carvalho de Melo <acme@...hat.com>,
        Kees Cook <kees@...nel.org>
Subject: Re: [patch V2 RESEND 3/6] perf/core: Split out VM accounting

On Mon, Aug 11, 2025 at 02:36:33PM +0200, Thomas Gleixner wrote:
> Similary to the mlock limit calculation the VM accounting is required for

NIT: Similary -> similarly

> both the ringbuffer and the AUX buffer allocations.
>
> To prepare for splitting them out into seperate functions, move the

NIT: seperate -> separate

> accounting into a helper function.
>
> Signed-off-by: Thomas Gleixner <tglx@...utronix.de>
> Reviewed-by: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
>
> ---
>  kernel/events/core.c |   13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
>
> --- a/kernel/events/core.c
> +++ b/kernel/events/core.c
> @@ -6962,10 +6962,17 @@ static bool perf_mmap_calc_limits(struct
>  	return locked <= lock_limit || !perf_is_paranoid() || capable(CAP_IPC_LOCK);
>  }
>
> +static void perf_mmap_account(struct vm_area_struct *vma, long user_extra, long extra)
> +{
> +	struct user_struct *user = current_user();
> +
> +	atomic_long_add(user_extra, &user->locked_vm);
> +	atomic64_add(extra, &vma->vm_mm->pinned_vm);
> +}
> +
>  static int perf_mmap(struct file *file, struct vm_area_struct *vma)
>  {
>  	struct perf_event *event = file->private_data;
> -	struct user_struct *user = current_user();
>  	unsigned long vma_size, nr_pages;
>  	long user_extra = 0, extra = 0;
>  	struct mutex *aux_mutex = NULL;
> @@ -7136,9 +7143,7 @@ static int perf_mmap(struct file *file,
>
>  unlock:
>  	if (!ret) {
> -		atomic_long_add(user_extra, &user->locked_vm);
> -		atomic64_add(extra, &vma->vm_mm->pinned_vm);
> -
> +		perf_mmap_account(vma, user_extra, extra);
>  		atomic_inc(&event->mmap_count);
>  	} else if (rb) {
>  		/* AUX allocation failed */
>
>
>