Re: [PATCH] [SCSI] mpt3sas: Added a driver module parameter max_msix_vectors

[Tomas Henzl <thenzl@redhat.com>]

On 08/14/2013 02:53 PM, Sreekanth Reddy wrote:
> Added a driver module parameter max_msix_vectors. Using this module parameter
> the maximum number of MSI-X vectors could be set.
>
> The number of MSI-X vectors used would be the minimum of MSI-X vectors supported by
> the HBA, the number of CPU cores and the value set to max_msix_vectors module parameter.
>
> The default value of this module parameter is set to 8. The default value of this parameter
> is set to 8 inorder to reduce the amount of memory required for Reply Descriptor Post queue.
> This is because with the higher MSI-X vectors, some times kernel is not able to allocate the
> requested amount of memory and crash is observed. To overcome this problem,
> the default value is set to 8.

Hi Sreekanth,
I don't know exactly which allocation fails, but wouldn't be for the user better to just try
to allocate and only when it fails lower the msi-x vectors count?
Tomas

>
> Signed-off-by: Sreekanth Reddy <Sreekanth.Reddy@lsi.com>
> --- 
>
> diff --git a/drivers/scsi/mpt3sas/mpt3sas_base.c b/drivers/scsi/mpt3sas/mpt3sas_base.c
> index a32d63b..d40ba0b 100644
> --- a/drivers/scsi/mpt3sas/mpt3sas_base.c
> +++ b/drivers/scsi/mpt3sas/mpt3sas_base.c
> @@ -82,6 +82,10 @@ static int msix_disable = -1;
>  module_param(msix_disable, int, 0);
>  MODULE_PARM_DESC(msix_disable, " disable msix routed interrupts (default=0)");
>  
> +static int max_msix_vectors = 8;
> +module_param(max_msix_vectors, int, 0);
> +MODULE_PARM_DESC(max_msix_vectors,
> +	" max msix vectors - (default=8)");
>  
>  static int mpt3sas_fwfault_debug;
>  MODULE_PARM_DESC(mpt3sas_fwfault_debug,
> @@ -1723,6 +1727,16 @@ _base_enable_msix(struct MPT3SAS_ADAPTER *ioc)
>  	ioc->reply_queue_count = min_t(int, ioc->cpu_count,
>  	    ioc->msix_vector_count);
>  
> +	printk(MPT3SAS_FMT "MSI-X vectors supported: %d, no of cores"
> +	  ": %d, max_msix_vectors: %d\n", ioc->name, ioc->msix_vector_count,
> +	  ioc->cpu_count, max_msix_vectors);
> +
> +	if (max_msix_vectors > 0) {
> +		ioc->reply_queue_count = min_t(int, max_msix_vectors,
> +			ioc->reply_queue_count);
> +		ioc->msix_vector_count = ioc->reply_queue_count;
> +	}
> +
>  	entries = kcalloc(ioc->reply_queue_count, sizeof(struct msix_entry),
>  	    GFP_KERNEL);
>  	if (!entries) {
>
> --
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