From: Mel Gorman <mgorman@suse.de>
To: Michel Lespinasse <walken@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Lin Feng <linfeng@cn.fujitsu.com>,
bcrl@kvack.org, viro@zeniv.linux.org.uk, khlebnikov@openvz.org,
kamezawa.hiroyu@jp.fujitsu.com, minchan@kernel.org,
riel@redhat.com, rientjes@google.com,
isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com,
laijs@cn.fujitsu.com, jiang.liu@huawei.com, linux-mm@kvack.org,
linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm: hotplug: implement non-movable version of get_user_pages() called get_user_pages_non_movable()
Date: Wed, 6 Feb 2013 10:41:17 +0000 [thread overview]
Message-ID: <20130206104117.GO21389@suse.de> (raw)
In-Reply-To: <CANN689GVFYTqs0wxX3bKZtyBcWf6=gLvS8hFG-65htsnPDknSA@mail.gmail.com>
On Tue, Feb 05, 2013 at 06:26:51PM -0800, Michel Lespinasse wrote:
> Just nitpicking, but:
>
> On Tue, Feb 5, 2013 at 3:57 AM, Mel Gorman <mgorman@suse.de> wrote:
> > +static inline bool zone_is_idx(struct zone *zone, enum zone_type idx)
> > +{
> > + /* This mess avoids a potentially expensive pointer subtraction. */
> > + int zone_off = (char *)zone - (char *)zone->zone_pgdat->node_zones;
> > + return zone_off == idx * sizeof(*zone);
> > +}
>
> Maybe:
> return zone == zone->zone_pgdat->node_zones + idx;
> ?
>
Not a nit at all. Yours is more readable but it generates more code. A
single line function that uses the helper generates 0x3f bytes of code
(mostly function entry/exit) with your version and 0x39 bytes with mine. The
difference in efficiency is marginal as your version uses lea to multiply
by a constant but it's still slightly heavier.
The old code is fractionally better, your version is more readable so it's
up to Andrew really. Right now I think he's gone with his own version with
zone_idx() in the name of readability whatever sparse has to say about
the matter.
--
Mel Gorman
SUSE Labs
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WARNING: multiple messages have this Message-ID (diff)
From: Mel Gorman <mgorman@suse.de>
To: Michel Lespinasse <walken@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>,
Lin Feng <linfeng@cn.fujitsu.com>,
bcrl@kvack.org, viro@zeniv.linux.org.uk, khlebnikov@openvz.org,
kamezawa.hiroyu@jp.fujitsu.com, minchan@kernel.org,
riel@redhat.com, rientjes@google.com,
isimatu.yasuaki@jp.fujitsu.com, wency@cn.fujitsu.com,
laijs@cn.fujitsu.com, jiang.liu@huawei.com, linux-mm@kvack.org,
linux-aio@kvack.org, linux-fsdevel@vger.kernel.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/2] mm: hotplug: implement non-movable version of get_user_pages() called get_user_pages_non_movable()
Date: Wed, 6 Feb 2013 10:41:17 +0000 [thread overview]
Message-ID: <20130206104117.GO21389@suse.de> (raw)
In-Reply-To: <CANN689GVFYTqs0wxX3bKZtyBcWf6=gLvS8hFG-65htsnPDknSA@mail.gmail.com>
On Tue, Feb 05, 2013 at 06:26:51PM -0800, Michel Lespinasse wrote:
> Just nitpicking, but:
>
> On Tue, Feb 5, 2013 at 3:57 AM, Mel Gorman <mgorman@suse.de> wrote:
> > +static inline bool zone_is_idx(struct zone *zone, enum zone_type idx)
> > +{
> > + /* This mess avoids a potentially expensive pointer subtraction. */
> > + int zone_off = (char *)zone - (char *)zone->zone_pgdat->node_zones;
> > + return zone_off == idx * sizeof(*zone);
> > +}
>
> Maybe:
> return zone == zone->zone_pgdat->node_zones + idx;
> ?
>
Not a nit at all. Yours is more readable but it generates more code. A
single line function that uses the helper generates 0x3f bytes of code
(mostly function entry/exit) with your version and 0x39 bytes with mine. The
difference in efficiency is marginal as your version uses lea to multiply
by a constant but it's still slightly heavier.
The old code is fractionally better, your version is more readable so it's
up to Andrew really. Right now I think he's gone with his own version with
zone_idx() in the name of readability whatever sparse has to say about
the matter.
--
Mel Gorman
SUSE Labs
next prev parent reply other threads:[~2013-02-06 10:41 UTC|newest]
Thread overview: 88+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-04 10:04 [PATCH 0/2] mm: hotplug: implement non-movable version of get_user_pages() to kill long-time pin pages Lin Feng
2013-02-04 10:04 ` Lin Feng
2013-02-04 10:04 ` [PATCH 1/2] mm: hotplug: implement non-movable version of get_user_pages() called get_user_pages_non_movable() Lin Feng
2013-02-04 10:04 ` Lin Feng
2013-02-04 10:04 ` Lin Feng
2013-02-05 0:06 ` Andrew Morton
2013-02-05 0:06 ` Andrew Morton
2013-02-05 0:06 ` Andrew Morton
2013-02-05 0:18 ` Andrew Morton
2013-02-05 0:18 ` Andrew Morton
2013-02-05 3:09 ` Lin Feng
2013-02-05 3:09 ` Lin Feng
2013-02-05 3:09 ` Lin Feng
2013-02-05 21:13 ` Andrew Morton
2013-02-05 21:13 ` Andrew Morton
2013-02-05 21:13 ` Andrew Morton
2013-02-05 11:57 ` Mel Gorman
2013-02-05 11:57 ` Mel Gorman
2013-02-05 11:57 ` Mel Gorman
2013-02-05 13:32 ` Mel Gorman
2013-02-05 13:32 ` Mel Gorman
2013-02-05 13:32 ` Mel Gorman
2013-02-19 13:37 ` Lin Feng
2013-02-19 13:37 ` Lin Feng
2013-02-20 2:34 ` Lin Feng
2013-02-20 2:34 ` Lin Feng
2013-02-20 2:34 ` Lin Feng
2013-02-20 2:44 ` Wanpeng Li
2013-02-20 2:44 ` Wanpeng Li
2013-02-20 2:44 ` Wanpeng Li
2013-02-20 2:59 ` Lin Feng
2013-02-20 2:59 ` Lin Feng
2013-02-20 9:58 ` Simon Jeons
2013-02-20 9:58 ` Simon Jeons
2013-02-20 10:23 ` Lin Feng
2013-02-20 10:23 ` Lin Feng
2013-02-20 10:23 ` Lin Feng
2013-02-20 11:31 ` Simon Jeons
2013-02-20 11:31 ` Simon Jeons
2013-02-20 11:54 ` Lin Feng
2013-02-20 11:54 ` Lin Feng
2013-02-20 11:54 ` Lin Feng
2013-02-06 2:26 ` Michel Lespinasse
2013-02-06 2:26 ` Michel Lespinasse
2013-02-06 2:26 ` Michel Lespinasse
2013-02-06 10:41 ` Mel Gorman [this message]
2013-02-06 10:41 ` Mel Gorman
2013-02-18 10:34 ` Lin Feng
2013-02-18 10:34 ` Lin Feng
2013-02-18 10:34 ` Lin Feng
2013-02-18 15:17 ` Mel Gorman
2013-02-18 15:17 ` Mel Gorman
2013-02-18 15:17 ` Mel Gorman
2013-02-19 9:55 ` Lin Feng
2013-02-19 9:55 ` Lin Feng
2013-02-19 10:34 ` Mel Gorman
2013-02-19 10:34 ` Mel Gorman
2013-02-19 10:34 ` Mel Gorman
2013-02-04 10:04 ` [PATCH 2/2] fs/aio.c: use get_user_pages_non_movable() to pin ring pages when support memory hotremove Lin Feng
2013-02-04 10:04 ` Lin Feng
2013-02-04 10:04 ` Lin Feng
2013-02-04 15:18 ` Jeff Moyer
2013-02-04 15:18 ` Jeff Moyer
2013-02-04 15:18 ` Jeff Moyer
2013-02-04 23:02 ` Zach Brown
2013-02-04 23:02 ` Zach Brown
2013-02-04 23:02 ` Zach Brown
2013-02-05 5:35 ` Lin Feng
2013-02-05 5:35 ` Lin Feng
2013-02-05 5:35 ` Lin Feng
2013-02-05 5:06 ` Lin Feng
2013-02-05 5:06 ` Lin Feng
2013-02-05 0:58 ` [PATCH 0/2] mm: hotplug: implement non-movable version of get_user_pages() to kill long-time pin pages Minchan Kim
2013-02-05 0:58 ` Minchan Kim
2013-02-05 0:58 ` Minchan Kim
2013-02-05 4:42 ` Lin Feng
2013-02-05 4:42 ` Lin Feng
2013-02-05 5:25 ` Minchan Kim
2013-02-05 5:25 ` Minchan Kim
2013-02-05 5:25 ` Minchan Kim
2013-02-05 6:18 ` Lin Feng
2013-02-05 6:18 ` Lin Feng
2013-02-05 7:45 ` Minchan Kim
2013-02-05 7:45 ` Minchan Kim
2013-02-05 7:45 ` Minchan Kim
2013-02-05 8:27 ` Lin Feng
2013-02-05 8:27 ` Lin Feng
2013-02-05 8:27 ` Lin Feng
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