linux-kernel - Re: [PATCH 1/1] mm/swap.c: flush lru_add pvecs on compound page arrival

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Date:	Wed, 8 Jun 2016 08:31:21 -0700
From:	Dave Hansen <dave.hansen@...el.com>
To:	Lukasz Odzioba <lukasz.odzioba@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	mhocko@...e.com, aarcange@...hat.com, vdavydov@...allels.com,
	mingli199x@...com, minchan@...nel.org
Cc:	lukasz.anaczkowski@...el.com
Subject: Re: [PATCH 1/1] mm/swap.c: flush lru_add pvecs on compound page
 arrival

On 06/08/2016 07:35 AM, Lukasz Odzioba wrote:
> diff --git a/mm/swap.c b/mm/swap.c
> index 9591614..3fe4f18 100644
> --- a/mm/swap.c
> +++ b/mm/swap.c
> @@ -391,9 +391,8 @@ static void __lru_cache_add(struct page *page)
>  	struct pagevec *pvec = &get_cpu_var(lru_add_pvec);
>  
>  	get_page(page);
> -	if (!pagevec_space(pvec))
> +	if (!pagevec_add(pvec, page) || PageCompound(page))
>  		__pagevec_lru_add(pvec);
> -	pagevec_add(pvec, page);
>  	put_cpu_var(lru_add_pvec);
>  }

Lukasz,

Do we have any statistics that tell us how many pages are sitting the
lru pvecs?  Although this helps the problem overall, don't we still have
a problem with memory being held in such an opaque place?

I think if we're going to be hacking around this area, we should also
add something to vmstat or zoneinfo to spell out how many of these
things there are.