linux-kernel - Re: [PATCH 1/3] IB/ehca: Replace vmalloc with kmalloc

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Date:	Wed, 22 Apr 2009 16:10:18 +0200
From:	michael <michael@...dence.eu.com>
To:	Stefan Roscher <ossrosch@...ux.vnet.ibm.com>
CC:	Roland Dreier <rdreier@...co.com>, fenkes@...ibm.com,
	LKML <linux-kernel@...r.kernel.org>,
	OF-EWG <ewg@...ts.openfabrics.org>,
	LinuxPPC-Dev <linuxppc-dev@...abs.org>, raisch@...ibm.com,
	alexschm@...ibm.com, stefan.roscher@...ibm.com
Subject: Re: [PATCH 1/3] IB/ehca: Replace vmalloc with kmalloc

Hi,

Stefan Roscher wrote:
> In case of large queue pairs there is the possibillity of allocation failures 
> due to memory fragmentationo with kmalloc().To ensure the memory is allocated even
> if kmalloc() can not find chunks which are big enough, we try to allocate the memory
> with vmalloc().
>
> Signed-off-by: Stefan Roscher <stefan.roscher@...ibm.com>
> ---
>
> On Tuesday 21 April 2009 07:34:30 pm Roland Dreier wrote:
>   
>>  > +	queue->queue_pages = kmalloc(nr_of_pages * sizeof(void *), GFP_KERNEL);
>>
>> How big might this buffer be?  Any chance of allocation failure due to
>> memory fragmentation?
>>
>>  - R.
>>     
> Hey Roland, 
> yes you are right and here is the patch to circumvent the described problem.
> It will apply on top of the patchset.
> regards Stefan
>
>   
I don't take the point, if it is not import use the vmalloc. Why you try 
with a kmalloc
alloc first? and why do not use kzalloc?
>  
>  drivers/infiniband/hw/ehca/ipz_pt_fn.c |   17 +++++++++++++----
>  1 files changed, 13 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/infiniband/hw/ehca/ipz_pt_fn.c b/drivers/infiniband/hw/ehca/ipz_pt_fn.c
> index a260559..1227c59 100644
> --- a/drivers/infiniband/hw/ehca/ipz_pt_fn.c
> +++ b/drivers/infiniband/hw/ehca/ipz_pt_fn.c
> @@ -222,8 +222,11 @@ int ipz_queue_ctor(struct ehca_pd *pd, struct ipz_queue *queue,
>  	/* allocate queue page pointers */
>  	queue->queue_pages = kmalloc(nr_of_pages * sizeof(void *), GFP_KERNEL);
>  	if (!queue->queue_pages) {
> -		ehca_gen_err("Couldn't allocate queue page list");
> -		return 0;
> +		queue->queue_pages = vmalloc(nr_of_pages * sizeof(void *));
> +		if (!queue->queue_pages) {
> +			ehca_gen_err("Couldn't allocate queue page list");
> +			return 0;
> +		}
>  	}
>  	memset(queue->queue_pages, 0, nr_of_pages * sizeof(void *));
>  
> @@ -240,7 +243,10 @@ int ipz_queue_ctor(struct ehca_pd *pd, struct ipz_queue *queue,
>  ipz_queue_ctor_exit0:
>  	ehca_gen_err("Couldn't alloc pages queue=%p "
>  		 "nr_of_pages=%x",  queue, nr_of_pages);
> -	kfree(queue->queue_pages);
> +	if (is_vmalloc_addr(queue->queue_pages))
> +		vfree(queue->queue_pages);
> +	else
> +		kfree(queue->queue_pages);
>  
>  	return 0;
>  }
> @@ -262,7 +268,10 @@ int ipz_queue_dtor(struct ehca_pd *pd, struct ipz_queue *queue)
>  			free_page((unsigned long)queue->queue_pages[i]);
>  	}
>  
> -	kfree(queue->queue_pages);
> +	if (is_vmalloc_addr(queue->queue_pages))
> +		vfree(queue->queue_pages);
> +	else
> +		kfree(queue->queue_pages);
>  
>  	return 1;
>  }
>   

Regards Michael
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