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 18:06:53 +0200
From:	Michal Hocko <mhocko@...nel.org>
To:	Dave Hansen <dave.hansen@...el.com>
Cc:	Lukasz Odzioba <lukasz.odzioba@...el.com>,
	linux-kernel@...r.kernel.org, linux-mm@...ck.org,
	akpm@...ux-foundation.org, kirill.shutemov@...ux.intel.com,
	aarcange@...hat.com, vdavydov@...allels.com, mingli199x@...com,
	minchan@...nel.org, lukasz.anaczkowski@...el.com
Subject: Re: [PATCH 1/1] mm/swap.c: flush lru_add pvecs on compound page
 arrival

On Wed 08-06-16 08:31:21, Dave Hansen wrote:
> 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?

Is it really worth bothering when we are talking about 56kB per CPU
(after this patch)?
-- 
Michal Hocko
SUSE Labs