linux-kernel - Re: [PATCH] mm/hugetlb: avoid unnecessary hugetlb_acct

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Message-ID: <853d6aa4-b84c-7ac2-00d4-402893fcf6b3@redhat.com>
Date:   Thu, 14 Jan 2021 13:32:03 +0100
From:   David Hildenbrand <david@...hat.com>
To:     Miaohe Lin <linmiaohe@...wei.com>, akpm@...ux-foundation.org,
        mike.kravetz@...cle.com
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/hugetlb: avoid unnecessary hugetlb_acct_memory() call

On 14.01.21 12:31, Miaohe Lin wrote:
> When gbl_reserve is 0, hugetlb_acct_memory() will do nothing except holding
> and releasing hugetlb_lock.

So, what's the deal then? Adding more code?

If this is a performance improvement, we should spell it out. Otherwise
I don't see a real benefit of this patch.

> 
> Signed-off-by: Miaohe Lin <linmiaohe@...wei.com>
> ---
>  mm/hugetlb.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> index 737b2dce19e6..fe2da9ad6233 100644
> --- a/mm/hugetlb.c
> +++ b/mm/hugetlb.c
> @@ -5241,7 +5241,8 @@ long hugetlb_unreserve_pages(struct inode *inode, long start, long end,
>  	 * reservations to be released may be adjusted.
>  	 */
>  	gbl_reserve = hugepage_subpool_put_pages(spool, (chg - freed));
> -	hugetlb_acct_memory(h, -gbl_reserve);
> +	if (gbl_reserve)
> +		hugetlb_acct_memory(h, -gbl_reserve);
>  
>  	return 0;
>  }
> 


-- 
Thanks,

David / dhildenb