Date: Thu, 26 Nov 2015 10:59:50 +0900
From: Joonsoo Kim <iamjoonsoo.kim@lge.com>
To: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
        Vlastimil Babka <vbabka@suse.cz>, Mel Gorman <mgorman@suse.de>,
        Yaowei Bai <bywxiaobai@163.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCH v2] mm/compaction: __compact_pgdat() code cleanuup
Message-ID: <20151126015950.GC13138@js1304-P5Q-DELUXE>
References: <1448429172-24961-1-git-send-email-iamjoonsoo.kim@lge.com>
 <alpine.DEB.2.10.1511250242100.32374@chino.kir.corp.google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.DEB.2.10.1511250242100.32374@chino.kir.corp.google.com>
User-Agent: Mutt/1.5.21 (2010-09-15)
Sender: linux-kernel-owner@vger.kernel.org
Content-Length: 2325
Lines: 67

On Wed, Nov 25, 2015 at 02:45:15AM -0800, David Rientjes wrote:
> On Wed, 25 Nov 2015, Joonsoo Kim wrote:
> 
> > This patch uses is_via_compact_memory() to distinguish direct compaction.
> 
> When I think of "direct compaction", I think of compaction triggered for 
> high-order allocations from the page allocator before direct reclaim.  
> This is the opposite of being triggered for is_via_compact_memory().

Okay. Will change it.

> 
> > And it also reduces indentation on compaction_defer_reset
> > by filtering failure case. There is no functional change.
> > 
> > Acked-by: Yaowei Bai <baiyaowei@cmss.chinamobile.com>
> > Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@lge.com>
> > ---
> >  mm/compaction.c | 13 +++++++------
> >  1 file changed, 7 insertions(+), 6 deletions(-)
> > 
> > diff --git a/mm/compaction.c b/mm/compaction.c
> > index de3e1e7..01b1e5e 100644
> > --- a/mm/compaction.c
> > +++ b/mm/compaction.c
> > @@ -1658,14 +1658,15 @@ static void __compact_pgdat(pg_data_t *pgdat, struct compact_control *cc)
> >  				!compaction_deferred(zone, cc->order))
> >  			compact_zone(zone, cc);
> >  
> > -		if (cc->order > 0) {
> > -			if (zone_watermark_ok(zone, cc->order,
> > -						low_wmark_pages(zone), 0, 0))
> > -				compaction_defer_reset(zone, cc->order, false);
> > -		}
> > -
> >  		VM_BUG_ON(!list_empty(&cc->freepages));
> >  		VM_BUG_ON(!list_empty(&cc->migratepages));
> > +
> > +		if (is_via_compact_memory(cc->order))
> > +			continue;
> 
> This will be the third call to is_via_compact_memory() in this function.  
> Maybe just do
> 
> 	const bool sysctl = is_via_compact_memory(cc->order);
> 
> early in the function since it won't change during the iteration?  (And 
> maybe get rid of that extra newline that already exists at the beginning 
> of the iteration?

I don't it's better. is_via_compact_memory() already express it's
meaning perfectly and no overhead here. Introducing extra variable
would confuse reader more than commonly used is_via_compact_memory().

> 
> Otherwise:
> 
> Acked-by: David Rientjes <rientjes@google.com>

Thanks.


--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@vger.kernel.org
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/