linux-kernel - Re: [PATCH] mm/mempolicy: fix NUMA_INTERLEAVE

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Date:   Tue, 3 Oct 2017 19:04:27 +0100
From:   Mel Gorman <mgorman@...hsingularity.net>
To:     Andrey Ryabinin <aryabinin@...tuozzo.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Kemi Wang <kemi.wang@...el.com>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm/mempolicy: fix NUMA_INTERLEAVE_HIT counter

On Tue, Oct 03, 2017 at 07:47:20PM +0300, Andrey Ryabinin wrote:
> Commit 3a321d2a3dde separated NUMA counters from zone counters, but
> the NUMA_INTERLEAVE_HIT call site wasn't updated to use the new interface.
> So alloc_page_interleave() actually increments NR_ZONE_INACTIVE_FILE
> instead of NUMA_INTERLEAVE_HIT.
> 
> Fix this by using __inc_numa_state() interface to increment
> NUMA_INTERLEAVE_HIT.
> 
> Fixes: 3a321d2a3dde ("mm: change the call sites of numa statistics items")
> Signed-off-by: Andrey Ryabinin <aryabinin@...tuozzo.com>
> ---
>  mm/mempolicy.c | 9 +++++++--
>  1 file changed, 7 insertions(+), 2 deletions(-)
> 
> diff --git a/mm/mempolicy.c b/mm/mempolicy.c
> index 006ba625c0b8..3a18f0a091c4 100644
> --- a/mm/mempolicy.c
> +++ b/mm/mempolicy.c
> @@ -1920,8 +1920,13 @@ static struct page *alloc_page_interleave(gfp_t gfp, unsigned order,
>  	struct page *page;
>  
>  	page = __alloc_pages(gfp, order, nid);
> -	if (page && page_to_nid(page) == nid)
> -		inc_zone_page_state(page, NUMA_INTERLEAVE_HIT);
> +	if (page && page_to_nid(page) == nid) {
> +		unsigned long flags;
> +
> +		local_irq_save(flags);
> +		__inc_numa_state(page_zone(page), NUMA_INTERLEAVE_HIT);
> +		local_irq_restore(flags);
> +	}
>  	return page;
>  }

alloc_page_interleave is only called from !irq contexts and the requirements
for __inc_numa_state should only require interrupt disabling if that
particular counter can be updated from interrupt context. Disabling
preemption should be sufficient for NUMA_INTERLEAVE_HIT and would be cheaper.

-- 
Mel Gorman
SUSE Labs