From: Andrew Morton <akpm@linux-foundation.org>
To: Minchan Kim <minchan@kernel.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>,
Michal Nazarewicz <mina86@mina86.com>
Subject: Re: [PATCH v2] mm: remove MIGRATE_ISOLATE check in hotpath
Date: Tue, 15 Jan 2013 15:36:25 -0800 [thread overview]
Message-ID: <20130115153625.96265439.akpm@linux-foundation.org> (raw)
In-Reply-To: <1358209006-18859-1-git-send-email-minchan@kernel.org>
On Tue, 15 Jan 2013 09:16:46 +0900
Minchan Kim <minchan@kernel.org> wrote:
> Now mm several functions test MIGRATE_ISOLATE and some of those
> are hotpath but MIGRATE_ISOLATE is used only if we enable
> CONFIG_MEMORY_ISOLATION(ie, CMA, memory-hotplug and memory-failure)
> which are not common config option. So let's not add unnecessary
> overhead and code when we don't enable CONFIG_MEMORY_ISOLATION.
ugh. Better than nothing, I guess.
There remain call sites which do open-coded
get_pageblock_migratetype(page) != MIGRATE_ISOLATE
(undo_isolate_page_range() is one). Wanna clean these up as well?
>
> ...
>
> @@ -683,7 +683,7 @@ static void free_one_page(struct zone *zone, struct page *page, int order,
> zone->pages_scanned = 0;
>
> __free_one_page(page, zone, order, migratetype);
> - if (unlikely(migratetype != MIGRATE_ISOLATE))
> + if (unlikely(!is_migrate_isolate(migratetype)))
> __mod_zone_freepage_state(zone, 1 << order, migratetype);
> spin_unlock(&zone->lock);
> }
The code both before and after this patch is assuming that the
migratetype in free_one_page is likely to be MIGRATE_ISOLATE. Seems
wrong. If CONFIG_MEMORY_ISOLATION=n this ends up doing
if(unlikely(true)) which is harmless-but-amusing.
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next prev parent reply other threads:[~2013-01-15 23:36 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-01-15 0:16 [PATCH v2] mm: remove MIGRATE_ISOLATE check in hotpath Minchan Kim
2013-01-15 8:43 ` Michal Nazarewicz
2013-01-15 23:36 ` Andrew Morton [this message]
2013-02-25 2:13 ` Minchan Kim
2013-02-25 22:50 ` Andrew Morton
2013-02-26 0:00 ` Minchan Kim
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