linux-kernel - Re: [PATCH v4 45/66] acct: Use VMA iterator instead of linked list

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Date:   Wed, 19 Jan 2022 17:44:05 +0100
From:   Vlastimil Babka <vbabka@...e.cz>
To:     Liam Howlett <liam.howlett@...cle.com>,
        "maple-tree@...ts.infradead.org" <maple-tree@...ts.infradead.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        Andrew Morton <akpm@...ux-foundation.org>
Cc:     Song Liu <songliubraving@...com>,
        Davidlohr Bueso <dave@...olabs.net>,
        "Paul E . McKenney" <paulmck@...nel.org>,
        Matthew Wilcox <willy@...radead.org>,
        Laurent Dufour <ldufour@...ux.ibm.com>,
        David Rientjes <rientjes@...gle.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        Suren Baghdasaryan <surenb@...gle.com>,
        Rik van Riel <riel@...riel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Michel Lespinasse <walken.cr@...il.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Minchan Kim <minchan@...gle.com>,
        Joel Fernandes <joelaf@...gle.com>,
        Rom Lemarchand <romlem@...gle.com>
Subject: Re: [PATCH v4 45/66] acct: Use VMA iterator instead of linked list

On 12/1/21 15:30, Liam Howlett wrote:
> From: "Liam R. Howlett" <Liam.Howlett@...cle.com>
> 
> The VMA iterator is faster than the linked list.
> 
> Signed-off-by: Matthew Wilcox (Oracle) <willy@...radead.org>
> Signed-off-by: Liam R. Howlett <Liam.Howlett@...cle.com>

Acked-by: Vlastimil Babka <vbabka@...e.cz>

> ---
>  kernel/acct.c | 11 +++++------
>  1 file changed, 5 insertions(+), 6 deletions(-)
> 
> diff --git a/kernel/acct.c b/kernel/acct.c
> index 3df53cf1dcd5..2e7bf8d41f04 100644
> --- a/kernel/acct.c
> +++ b/kernel/acct.c
> @@ -535,15 +535,14 @@ void acct_collect(long exitcode, int group_dead)
>  	unsigned long vsize = 0;
>  
>  	if (group_dead && current->mm) {
> +		struct mm_struct *mm = current->mm;
> +		VMA_ITERATOR(vmi, mm, 0);
>  		struct vm_area_struct *vma;
>  
> -		mmap_read_lock(current->mm);
> -		vma = current->mm->mmap;
> -		while (vma) {
> +		mmap_read_lock(mm);
> +		for_each_vma(vmi, vma)
>  			vsize += vma->vm_end - vma->vm_start;
> -			vma = vma->vm_next;
> -		}
> -		mmap_read_unlock(current->mm);
> +		mmap_read_unlock(mm);
>  	}
>  
>  	spin_lock_irq(&current->sighand->siglock);