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Date: Fri, 1 Jul 2016 08:21:21 +0900
From: Byungchul Park <byungchul.park@lge.com>
To: Peter Zijlstra <peterz@infradead.org>
Cc: mingo@kernel.org, linux-kernel@vger.kernel.org, npiggin@suse.de,
        walken@google.com, ak@suse.de, tglx@inhelltoy.tec.linutronix.de
Subject: Re: [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock
Message-ID: <20160630232121.GT2279@X58A-UD3R>
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On Thu, Jun 30, 2016 at 03:04:58PM +0200, Peter Zijlstra wrote:
> On Mon, Jun 20, 2016 at 01:55:23PM +0900, Byungchul Park wrote:
> > @@ -215,6 +219,11 @@ struct page {
> >  #ifdef LAST_CPUPID_NOT_IN_PAGE_FLAGS
> >  	int _last_cpupid;
> >  #endif
> > +
> > +#ifdef CONFIG_LOCKDEP_PAGELOCK
> > +	struct lockdep_map map;
> > +	struct cross_lock xlock;
> > +#endif
> >  }
> 
> So that's 32+64=96 bytes (CONFIG_LOCK_STAT=n) added to struct page,
> really!?

Yes... I concerned it at first, but I thought it would be ok since
CONFIG_LOCKDEP_PAGE is a debug feature. Anyway, I will try to reduce
the size of struct cross_lock which is only thing I can do to reduce
it, since we cannot avoid using lockdep_map if we want to make
lock_page() participate in the lockdep play.