linux-kernel - Re: [PATCH] mm: compare MIGRATE

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Message-ID: <20121223231547.GA2453@blaptop>
Date:	Mon, 24 Dec 2012 08:26:39 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Michal Nazarewicz <mina86@...a86.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: compare MIGRATE_ISOLATE selectively

On Fri, Dec 21, 2012 at 01:46:23PM +0100, Michal Nazarewicz wrote:
> > On Thu, Dec 20, 2012 at 04:49:44PM +0100, Michal Nazarewicz wrote:
> >> Perhaps “is_migrate_isolate” to match already existing “is_migrate_cma”?
> 
> On Fri, Dec 21 2012, Minchan Kim wrote:
> > Good poking. In fact, while I made this patch, I was very tempted by renaming
> > is_migrate_cma to cma_pageblock.
> >
> >         is_migrate_cma(mt)
> >
> > I don't know who start to use "mt" instead of "migratetype" but anyway, it's
> > not a good idea.
> >
> >         is_migrate_cma(migratetype)
> >
> > It's very clear for me because migratetype is per pageblock, we can know the
> > function works per pageblock unit.
> >
> >> Especially as the “mt_isolated_pageblock” sound confusing to me, it
> >> implies that it works on pageblocks which it does not.
> >
> > -ENOPARSE.
> >
> > migratetype works on pageblock.
> 
> migratetype is a number, which can be assigned to a pageblock.  In some
> transitional cases, the migratetype associated with a page can differ
> from the migratetype associated with the pageblock the page is in.  As
> such, I think it's confusing to add “pageblock” to the name of the
> function which does not read migratetype from pageblock but rather
> operates on the number it is provided.

Fair enough.

> 
> > I admit mt is really dirty but I used page_alloc.c already has lots of
> > mt, SIGH.
> 
> I don't really have an issue with “mt” myself, especially since the few
> times “mt” is used in page_alloc.c it is a local variable which I don't
> think needs a long descriptive name since context is all there.
> 
> > How about this?
> >
> > 1. Let's change all "mt" with "migratetype" again.
> > 2. use is_migrate_isolate and is_migrate_cma for "migratetype".
> > 3. use is_migrate_isolate_page instead of page_isolated_pageblock for
> >    "page".
> 
> Like I've said.  Personally I don't really think 1 is needed, but 2 and
> 3 look good to me.

Okay. It would be a first patch in New Year.
Thanks for the review, Michal.

> 
> -- 
> Best regards,                                         _     _
> .o. | Liege of Serenely Enlightened Majesty of      o' \,=./ `o
> ..o | Computer Science,  Michał “mina86” Nazarewicz    (o o)
> ooo +----<email/xmpp: mpn@...gle.com>--------------ooO--(_)--Ooo--





-- 
Kind regards,
Minchan Kim
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