linux-kernel - Re: [PATCH 2.6.28-rc4]lock_stat: Add "con-hungry" to show that how many person-time fight for the ticket spinlock

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Date:	Sun, 23 Nov 2008 02:40:26 +0100
From:	Peter Zijlstra <a.p.zijlstra@...llo.nl>
To:	Yang Xi <yangxilkm@...il.com>
Cc:	linux-kernel@...r.kernel.org, mingo@...e.hu,
	chyyuu <chyyuu@...il.com>
Subject: Re: [PATCH 2.6.28-rc4]lock_stat: Add "con-hungry" to show that how
 many person-time fight for the ticket spinlock

On Thu, 2008-11-20 at 16:09 +0800, Yang Xi wrote:
> > I of course meant folding cpu and isspinlock into a combined bitfield
> > (sorry for not being more clear), thereby saving space, this still takes
> > 2*sizeof(int).
> >
> > We can safely take some bits from the cpu number as there currently are
> > no plans for a 2g cpu machine, right SGI? :-)
> Thanks, ok, 31bits enough for cpu at now stage. 1bit for isticketspinlock.
> Here is the new one. Welcome more comments :).

Looks good, one more question :-)

> --- a/include/linux/spinlock.h
> +++ b/include/linux/spinlock.h
> @@ -127,6 +127,12 @@ do {
>                  \
>  #define spin_is_contended(lock)
> __raw_spin_is_contended(&(lock)->raw_lock)
>  #endif
> 
> +#ifdef CONFIG_HAVE_TICKET_SPINLOCK
> +#define spin_nr_contended(lock) __ticket_spin_nr_contended(&(lock)->raw_lock)
> +#else
> +#define spin_nr_contended(lock) (0)
> +#endif
> +

Does it make sense to make the alternative case return
spin_is_contended()?

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