Re: [PATCH 1/3] ipr: Reduce queuecommand lock time

[Matthew Wilcox <matthew@wil.cx>]

On Mon, Jul 16, 2012 at 03:48:08PM -0500, Brian King wrote:
> +static int ipr_queuecommand(struct Scsi_Host *shost,
> +			    struct scsi_cmnd *scsi_cmd)
>  {
>  	struct ipr_ioa_cfg *ioa_cfg;
>  	struct ipr_resource_entry *res;
>  	struct ipr_ioarcb *ioarcb;
>  	struct ipr_cmnd *ipr_cmd;
> +	unsigned long lock_flags = 0;

You don't need to initialise lock_flags.

Looking at the rest of the code, you drop the lock in the middle,
then re-acquire it.  That'll help with hold time, but I'm not convinced
it'll help with performance.  Have you done performance testing with
these changes?  I seem to remember we used an eight-socket box to show
host_lock problems in the past.

-- 
Matthew Wilcox				Intel Open Source Technology Centre
"Bill, look, we understand that you're interested in selling us this
operating system, but compare it to ours.  We can't possibly take such
a retrograde step."