linux-kernel - Re: [RFC PATCH v2 06/12] fs: proc: use pageblock_nr_pages for reschedule period in read

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Message-ID: <30dd7d1f-df39-ad89-94aa-d1562b84fa8b@redhat.com>
Date:   Tue, 23 Aug 2022 12:36:15 +0200
From:   David Hildenbrand <david@...hat.com>
To:     Zi Yan <ziy@...dia.com>, linux-mm@...ck.org
Cc:     Matthew Wilcox <willy@...radead.org>,
        Vlastimil Babka <vbabka@...e.cz>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        John Hubbard <jhubbard@...dia.com>,
        Yang Shi <shy828301@...il.com>,
        David Rientjes <rientjes@...gle.com>,
        James Houghton <jthoughton@...gle.com>,
        Mike Rapoport <rppt@...nel.org>, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH v2 06/12] fs: proc: use pageblock_nr_pages for
 reschedule period in read_kcore()

On 12.08.22 01:16, Zi Yan wrote:
> From: Zi Yan <ziy@...dia.com>
> 
> MAX_ORDER_NR_PAGES can be increased when it becomes a boot time parameter
> in later commits. To make sure read_kcore() reschedule its work in a
> constant period, use pageblock_nr_pages instead for reschedule period,
> since pageblock_nr_pages is a constant and either the same or half of
> MAX_ORDER_NR_PAGES.
> 
> Signed-off-by: Zi Yan <ziy@...dia.com>
> Cc: Mike Rapoport <rppt@...nel.org>
> Cc: David Hildenbrand <david@...hat.com>
> Cc: Oscar Salvador <osalvador@...e.de>
> Cc: Ying Chen <chenying.kernel@...edance.com>
> Cc: Feng Zhou <zhoufeng.zf@...edance.com>
> Cc: linux-fsdevel@...r.kernel.org
> Cc: linux-mm@...ck.org
> Cc: linux-kernel@...r.kernel.org
> ---
>  fs/proc/kcore.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/fs/proc/kcore.c b/fs/proc/kcore.c
> index dff921f7ca33..7dc09d211b48 100644
> --- a/fs/proc/kcore.c
> +++ b/fs/proc/kcore.c
> @@ -491,7 +491,7 @@ read_kcore(struct file *file, char __user *buffer, size_t buflen, loff_t *fpos)
>  			}
>  		}
>  
> -		if (page_offline_frozen++ % MAX_ORDER_NR_PAGES == 0) {
> +		if (page_offline_frozen++ % pageblock_nr_pages == 0) {
>  			page_offline_thaw();
>  			cond_resched();
>  			page_offline_freeze();

Yeah, the exact number doesn't actually matter here.

Reviewed-by: David Hildenbrand <david@...hat.com>

-- 
Thanks,

David / dhildenb