linux-kernel - Re: [PATCH][RFC] dirty balancing for cgroups

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Message-Id: <20080813071505.930965A75@siro.lan>
Date:	Wed, 13 Aug 2008 16:15:05 +0900 (JST)
From:	yamamoto@...inux.co.jp (YAMAMOTO Takashi)
To:	a.p.zijlstra@...llo.nl
Cc:	kamezawa.hiroyu@...fujitsu.com, linux-mm@...ck.org,
	menage@...gle.com, containers@...ts.linux-foundation.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH][RFC] dirty balancing for cgroups

hi,

> > @@ -485,7 +502,10 @@ unsigned long mem_cgroup_isolate_pages(unsigned long nr_to_scan,
> >  		if (PageUnevictable(page) ||
> >  		    (PageActive(page) && !active) ||
> >  		    (!PageActive(page) && active)) {
> > -			__mem_cgroup_move_lists(pc, page_lru(page));
> > +			if (try_lock_page_cgroup(page)) {
> > +				__mem_cgroup_move_lists(pc, page_lru(page));
> > +				unlock_page_cgroup(page);
> > +			}
> >  			continue;
> >  		}
> 
> This chunk seems unrelated and lost....

it's necessary to protect from mem_cgroup_{set,clear}_dirty
which modify pc->flags without holding mz->lru_lock.

> I presonally dislike the != 0, == 0 comparisons for bitmask operations,
> they seem to make it harder to read somewhow. I prefer to write !(flags
> & mask) and (flags & mask), instead.
> 
> I guess taste differs,...

yes, it seems different. :)

YAMAMOTO Takashi
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