linux-kernel - Re: [PATCH V5 4/6] mm: reclaim MADV

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Message-ID: <20170227163212.GN26504@dhcp22.suse.cz>
Date:   Mon, 27 Feb 2017 17:32:12 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Shaohua Li <shli@...com>
Cc:     Minchan Kim <minchan@...nel.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, Kernel-team@...com, hughd@...gle.com,
        hannes@...xchg.org, riel@...hat.com, mgorman@...hsingularity.net,
        akpm@...ux-foundation.org
Subject: Re: [PATCH V5 4/6] mm: reclaim MADV_FREE pages

On Mon 27-02-17 08:19:08, Shaohua Li wrote:
> On Mon, Feb 27, 2017 at 03:33:15PM +0900, Minchan Kim wrote:
[...]
> > > --- a/include/linux/rmap.h
> > > +++ b/include/linux/rmap.h
> > > @@ -298,6 +298,6 @@ static inline int page_mkclean(struct page *page)
> > >  #define SWAP_AGAIN	1
> > >  #define SWAP_FAIL	2
> > >  #define SWAP_MLOCK	3
> > > -#define SWAP_LZFREE	4
> > > +#define SWAP_DIRTY	4
> > 
> > I still don't convinced why we should introduce SWAP_DIRTY in try_to_unmap.
> > https://marc.info/?l=linux-mm&m=148797879123238&w=2
> > 
> > We have been SetPageMlocked in there but why cannot we SetPageSwapBacked
> > in there? It's not a thing to change LRU type but it's just indication
> > we found the page's status changed in late.
> 
> This one I don't have strong preference. Personally I agree with Johannes,
> handling failure in vmscan sounds better. But since the failure handling is
> just one statement, this probably doesn't make too much difference. If Johannes
> and you made an agreement, I'll follow.

FWIW I like your current SWAP_DIRTY and the later handling at the vmscan
level more.
-- 
Michal Hocko
SUSE Labs