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

[Waiman Long <waiman.long@hp.com>]

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