Re: [PATCH v4 1/3] qspinlock: Introducing a 4-byte queue spinlock implementation

[Waiman Long]

On 02/18/2014 02:30 AM, Peter Zijlstra wrote:
> On Mon, Feb 17, 2014 at 03:41:22PM -0500, Waiman Long wrote:
> > +/*
> > + * The queue node structure
> > + *
> > + * This structure is essentially the same as the mcs_spinlock structure
> > + * in mcs_spinlock.h file. This structure is retained for future extension
> > + * where new fields may be added.
> > + */
> > +struct qnode {
> > +	u32		 wait;		/* Waiting flag		*/
> > +	struct qnode	*next;		/* Next queue node addr */
> > +};
> > +
> > +struct qnode_set {
> > +	int		node_idx;	/* Current node to use */
> > +	struct qnode	nodes[MAX_QNODES];
> > +};
> > +
> > +/*
> > + * Per-CPU queue node structures
> > + */
> > +static DEFINE_PER_CPU(struct qnode_set, qnset) ____cacheline_aligned
> > +	= { 0 };
> You really didn't pay attention did you.
>
> That should be DEFINE_PER_CPU_ALIGNED()
>
> Furthermore, your structure is bigger than 1 cacheline; your struct
> qnode is 16 bytes, 4*16=64, and then you add that int.

Thank for letting me know about that. This is a minor problem that I 
will fix in the next version.

-Longman
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