Re: [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock

From	"Kirill A. Shutemov" <kirill@shutemov.name>
Newsgroups	linux.kernel
Subject	Re: [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock
Date	2016-07-01 13:30 +0200
Message-ID	<rQ4NX-60Z-1@gated-at.bofh.it> (permalink)
References	<rLZMR-42g-3@gated-at.bofh.it> <rLZMS-42g-33@gated-at.bofh.it> <rPJTc-1y9-15@gated-at.bofh.it> <rPTzb-7lm-7@gated-at.bofh.it>
Organization	linux.* mail to news gateway

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On Fri, Jul 01, 2016 at 08:21:21AM +0900, Byungchul Park wrote:
> 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.

Please use page_ext instead. With boottime switch to enable.

This way we can have this compile-time debug option enabled on more
machines without unnecessary runtime overhead.

And, please, CC linux-mm next time.

-- 
 Kirill A. Shutemov

Thread

Re: [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock Peter Zijlstra <peterz@infradead.org> - 2016-06-30 15:10 +0200
  Re: [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock Byungchul Park <byungchul.park@lge.com> - 2016-07-01 01:30 +0200
    Re: [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock Peter Zijlstra <peterz@infradead.org> - 2016-07-01 10:20 +0200
    Re: [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock "Kirill A. Shutemov" <kirill@shutemov.name> - 2016-07-01 13:30 +0200
      Re: [RFC 08/12] lockdep: Apply crossrelease to PG_locked lock Byungchul Park <byungchul.park@lge.com> - 2016-07-04 06:40 +0200

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