linux-kernel - Re: [Update][PATCH v5 7/9] mm/swap: Add cache for swap slots allocation

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Date:   Wed, 18 Jan 2017 19:15:21 +0100
From:   Michal Hocko <mhocko@...nel.org>
To:     Tim Chen <tim.c.chen@...ux.intel.com>
Cc:     "Huang, Ying" <ying.huang@...el.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        dave.hansen@...el.com, ak@...ux.intel.com, aaron.lu@...el.com,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Hugh Dickins <hughd@...gle.com>, Shaohua Li <shli@...nel.org>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Johannes Weiner <hannes@...xchg.org>,
        Hillf Danton <hillf.zj@...baba-inc.com>,
        Christian Borntraeger <borntraeger@...ibm.com>,
        Jonathan Corbet <corbet@....net>,
        Tim C Chen <tim.c.chen@...el.com>
Subject: Re: [Update][PATCH v5 7/9] mm/swap: Add cache for swap slots
 allocation

On Wed 18-01-17 10:03:27, Tim Chen wrote:
> On Wed, Jan 18, 2017 at 01:45:55PM +0100, Michal Hocko wrote:
> > On Tue 17-01-17 13:42:35, Tim Chen wrote:
> > [...]
> > > Logic wise, We do allow pre-emption as per cpu ptr cache->slots is
> > > protected by the mutex cache->alloc_lock.  We switch the
> > > inappropriately used this_cpu_ptr to raw_cpu_ptr for per cpu ptr
> > > access of cache->slots.
> > 
> > OK, that looks better. I would still appreciate something like the
> > following folded in
> > diff --git a/include/linux/swap_slots.h b/include/linux/swap_slots.h
> > index fb907346c5c6..0afe748453a7 100644
> > --- a/include/linux/swap_slots.h
> > +++ b/include/linux/swap_slots.h
> > @@ -11,6 +11,7 @@
> >  
> >  struct swap_slots_cache {
> >  	bool		lock_initialized;
> > +	/* protects slots, nr, cur */
> >  	struct mutex	alloc_lock;
> >  	swp_entry_t	*slots;
> >  	int		nr;
> > 
> 
> I've included here a patch for the comments.

Thanks!
-- 
Michal Hocko
SUSE Labs